Author Topic: RDRSSTC - Project Build  (Read 9396 times)

Offline ZakW

  • High Voltage Technician
  • ***
  • Posts: 179
  • Karma: +6/-0
  • YouTube @QZW_Labs
    • View Profile
RDRSSTC - Project Build
« on: October 01, 2023, 11:01:03 PM »
Hello,

While I am still wrapping up my RSSTC I'd like to start planning my next build. For that I want to step up to DRSSTC territory. I want this to be a ramped coil as well that will hopefully help prepare me for a QCWDRSSTC in the future.



High level plan:

My aim is a compact design with the best secondary to arc length ratio.



Driver Questions:
  • Considering the UD1.3b, how crucial is phase lead? I've noticed it in later UD versions. Should I integrate it into UD1.3? https://kaizerpowerelectronics.dk/files/stevehv.4hv.org_files/universal_driver_1.3b/DRSSTC_pndriver1_3b.pdf
  • For a more compact RDRSSTC, would driving the IGBTs at around 18-20v vs. the UCC27423's 15v max make a significant difference, considering the improvement in current capabilities?
  • Can I bypass the push/pull MOSFET output stage and simply use two UCC27423s, given that a single UCC27425 was adequate for my half bridge RSSTC?
  • Are there notable differences between regular and ramped DRSSTCs in terms of component stress and operation, aside from the arc appearance?



Thank you!
 
« Last Edit: October 03, 2023, 02:09:20 AM by ZakW »

Offline Lucasww

  • High Voltage Experimenter
  • **
  • Posts: 51
  • Karma: +4/-0
    • View Profile
Re: RDRSSTC - Project Build
« Reply #1 on: October 03, 2023, 08:21:23 AM »
Phase lead will be very helpful if you are planning to run long on-times, which you will be doing with a ramped coil.

With 15v input on your GDT, assuming 1:1 turns ratio, you will realistically be able to get 13-14v consistently on your igbt gates. The FGH75T65SHD datasheet shows that they should be fine at that voltage. However, what concerns me more is the possibility of ringing on your gates causing the voltage to drop potentially below 10v, which could easily cause desaturation. This isn't as much of an issue with the typical 18-24v gate drive most use. I'm using FGH75T65SHD in my QCWDRSSTC and have had no issues driving them at 19v.

Whether or not you can bypass the output mosfets is really up to what gate drive voltage you want. If you want the voltage to be above 15v, you will either need the mosfets, or a higher voltage gate drive chip. Most higher voltage chips with suitable rise times and propagation delays are SMD and quite small, so you may have trouble keeping them cool. I would recommend just using the mosfets.

As far as operation and component stress, You will generally want higher coupling, and a higher impedance primary circuit. The stress on your components ultimately depends on tuning, current and on-time. Properly tuned phase lead will greatly reduce switching stress, especially with long on-time.

Offline ZakW

  • High Voltage Technician
  • ***
  • Posts: 179
  • Karma: +6/-0
  • YouTube @QZW_Labs
    • View Profile
Re: RDRSSTC - Project Build
« Reply #2 on: October 03, 2023, 07:36:37 PM »
Hello Lucasww, I appreciate the insight!

Quote
Phase lead will be very helpful if you are planning to run long on-times, which you will be doing with a ramped coil.
Thank you for confirming that. I will see about adding it. I assume I can copy the phase lead portion from the UD2.7 into the UD1.3?

I would like to build the UD1.3 from scratch, is that typically not advised? It would be a good chunk of work but give me a lot of experience using PCB software, I have an okay foundation. Ideally, I would have the whole DRSSTC on one PCB or at most two. Similar to Loneoceans full bridge SSTC build on a single PCB.

Quote
With 15v input on your GDT, assuming 1:1 turns ratio, you will realistically be able to get 13-14v consistently on your igbt gates. The FGH75T65SHD datasheet shows that they should be fine at that voltage. However, what concerns me more is the possibility of ringing on your gates causing the voltage to drop potentially below 10v, which could easily cause desaturation. This isn't as much of an issue with the typical 18-24v gate drive most use. I'm using FGH75T65SHD in my QCWDRSSTC and have had no issues driving them at 19v.
Looking back on some scope captures of my gate drive signal from my SSTC using a UCC27425 at 15V Vcc I was getting 15.6-16V on the gate. I used a commercial 1:1 GDT.  Not quite as low as you mentioned but it sounds like a good idea to include the push/pull stage to achieve a higher gate drive voltage. I will aim for 18v or so.

Quote
As far as operation and component stress, You will generally want higher coupling, and a higher impedance primary circuit. The stress on your components ultimately depends on tuning, current and on-time. Properly tuned phase lead will greatly reduce switching stress, especially with long on-time.
I have read that higher coupling and impedance is beneficial. Is a higher impedance achieved by more primary turns and a smaller resonant capacitor?

Good to hear that phase lead is so effective!


Thanks again!



Offline Lucasww

  • High Voltage Experimenter
  • **
  • Posts: 51
  • Karma: +4/-0
    • View Profile
Re: RDRSSTC - Project Build
« Reply #3 on: October 07, 2023, 08:51:39 AM »
Quote
I would like to build the UD1.3 from scratch, is that typically not advised? It would be a good chunk of work but give me a lot of experience using PCB software, I have an okay foundation. Ideally, I would have the whole DRSSTC on one PCB or at most two. Similar to Loneoceans full bridge SSTC build on a single PCB.
Building a board from scratch is fine, although it is quite a bit more work, as you mentioned. make sure you use large ground planes to help avoid interference, which is an issue when driving tesla coils.

Quote
Looking back on some scope captures of my gate drive signal from my SSTC using a UCC27425 at 15V Vcc I was getting 15.6-16V on the gate. I used a commercial 1:1 GDT.  Not quite as low as you mentioned but it sounds like a good idea to include the push/pull stage to achieve a higher gate drive voltage. I will aim for 18v or so.
Interesting that you got higher voltages on the gate than you have on the input. Still, the mosfet push/pull buffer is a good idea. 18v should be perfectly fine.

Quote
I have read that higher coupling and impedance is beneficial. Is a higher impedance achieved by more primary turns and a smaller resonant capacitor?
Yes. For QCW coils with >20ms on-time people usually use 7-15nF capacitance, and whatever inductance gives the right frequency. For a mains-ramped coil, your ontime will be probably under 5ms, so slightly more capacitance may be good to get a bit more current. Maybe somewhere around 20-30nF. Typical DRSSTCs use much higher capacitances like 100-500nF

Offline Mads Barnkob

  • Administrator
  • Executive Board Member
  • *****
  • Posts: 2243
  • Karma: +70/-0
  • Denmark
    • View Profile
    • Kaizer Power Electronics
Re: RDRSSTC - Project Build
« Reply #4 on: October 11, 2023, 07:38:51 PM »
Quote
Looking back on some scope captures of my gate drive signal from my SSTC using a UCC27425 at 15V Vcc I was getting 15.6-16V on the gate. I used a commercial 1:1 GDT.  Not quite as low as you mentioned but it sounds like a good idea to include the push/pull stage to achieve a higher gate drive voltage. I will aim for 18v or so.
Interesting that you got higher voltages on the gate than you have on the input. Still, the mosfet push/pull buffer is a good idea. 18v should be perfectly fine.

A high voltage could indicate that you have ringing being rectified or your measurements are not fast enough to capture the ringing.

Why not drive the gates even harder, if you are worried about switching losses? Usually 24VDC is used in the UD1.x/UD2.x drivers. Limiting gate voltage in commercial applications is a way to limit the C-E maximum current, we are beyond trying to nurse our IGBTs like that.
https://kaizerpowerelectronics.dk - Tesla coils, high voltage, pulse power, audio and general electronics
https://www.youtube.com/KaizerPowerElectronicsDk60/join - Please consider supporting the forum, websites and youtube channel!

Offline ZakW

  • High Voltage Technician
  • ***
  • Posts: 179
  • Karma: +6/-0
  • YouTube @QZW_Labs
    • View Profile
Re: RDRSSTC - Project Build
« Reply #5 on: October 11, 2023, 09:14:42 PM »
Quote
Building a board from scratch is fine, although it is quite a bit more work, as you mentioned. make sure you use large ground planes to help avoid interference, which is an issue when driving tesla coils.
I already started, much more complicated than my last SSTC. Going to be a lot of work.

Quote
Yes. For QCW coils with >20ms on-time people usually use 7-15nF capacitance, and whatever inductance gives the right frequency. For a mains-ramped coil, your ontime will be probably under 5ms, so slightly more capacitance may be good to get a bit more current. Maybe somewhere around 20-30nF. Typical DRSSTCs use much higher capacitances like 100-500nF
Good to know, I will keep this in mind!

Quote
A high voltage could indicate that you have ringing being rectified or your measurements are not fast enough to capture the ringing.
Quote
Interesting that you got higher voltages on the gate than you have on the input. Still, the mosfet push/pull buffer is a good idea. 18v should be perfectly fine.
Regarding the higher gate voltage. I attached a picture of my SSTC gate waveform. It is at 15.6V so probably a little bit of ringing, other than that I think it looks great.



Quote
Why not drive the gates even harder, if you are worried about switching losses? Usually 24VDC is used in the UD1.x/UD2.x drivers. Limiting gate voltage in commercial applications is a way to limit the C-E maximum current, we are beyond trying to nurse our IGBTs like that.
Haha great point, Mads! I was planning on driving them at a higher voltage but just never landed on a value. I agree though, no real point in going easy on them given how they are being used.




Offline Lucasww

  • High Voltage Experimenter
  • **
  • Posts: 51
  • Karma: +4/-0
    • View Profile
Re: RDRSSTC - Project Build
« Reply #6 on: October 11, 2023, 10:25:23 PM »
Waveforms look great. You might be able to get away with slightly less gate resistance for faster transitions, but it's probably perfectly good as is, especially if you decide to raise the voltage

Offline ZakW

  • High Voltage Technician
  • ***
  • Posts: 179
  • Karma: +6/-0
  • YouTube @QZW_Labs
    • View Profile
Re: RDRSSTC - Project Build
« Reply #7 on: October 12, 2023, 12:43:59 AM »
Quote
Waveforms look great. You might be able to get away with slightly less gate resistance for faster transitions, but it's probably perfectly good as is, especially if you decide to raise the voltage

Thank you. Just to clarify that scope capture was the gate drive from my Ramped SSTC that I was referencing when looking at potentially excluding the push/pull buffer stage from the UD1.3.

For a coil like this, providing a higher gate drive voltage seems to be the best way to go. I will be sure to include the push/pull buffer so I can increase the voltage.


Offline ZakW

  • High Voltage Technician
  • ***
  • Posts: 179
  • Karma: +6/-0
  • YouTube @QZW_Labs
    • View Profile
Re: RDRSSTC - Project Build
« Reply #8 on: December 23, 2023, 10:49:07 PM »
Hello,

Picked this project back up and have a few questions before I start working on the PCB.

1. Half wave vs full wave rectification for the bridge - I used a single diode in my RSSTC for halfwave rectification for the bridge. It was a SMD 600v 10A 100A peak standard diode, never had any failures with it. Since this is a Ramped DRSSTC currents should be much higher. My assumption is that a full bridge part/package would be better suited to handle the power and heat dissipation, could I also get away with using a beefier single diode instead? Although, I never did have a heating issue with using a single diode in my RSSTC. I am not sure which solution is better.
       - If I use a full bridge but my ZCD is only half wave rectification via a single 1N4148, would there be an issue with the bridge being powered from both cycles instead of just the half cycles like with a single diode? The ZCD wont trigger and power the
               bridge on for all cycles since it is only outputting a signal on the positive half cycle, which is fine. I only run the interrupter at low BPS, I don't care much for higher BPS.

2. I am aiming for as little bridge inductance as possible but I would still like to include TVS diodes across CE. Are two 1.5kW 220V in series better or can I get away with a single diode 1.5kW 400v type for each?
       - 220v https://www.mouser.com/ProductDetail/652-1.5SMC220CA
       - 400v https://www.mouser.com/ProductDetail/576-1.5SMC400CA

3.Since I am trying to simplify the design a bit I really just added the phase adjust to the UD 1.3b. However, the push/pull transistor stage parts after the UCC27423 are outdated. I have seen other use IRF530/IRF9530, 100v 17A parts but I don't think I need such highly rated MOSFETs. Plus they have much high Qg compared to lower voltage parts. While I have found other parts with better characteristics https://www.mouser.com/ProductDetail/Diodes-Incorporated/DMN6068LK3-13?qs=4YT44p7w2bsq47X783VrzA%3D%3D it is hard to find if they have a PNP counterpart, like the IRF530 vs the IRF9530. Does anyone know of a way to identify a close alternative for a complimentary NPN/PNP stage?
       - Most PNP parts I have found differ slightly, is this expected and still usable or should Vdss and Id match a close as possible?
       - Example of something that might match the PNP DMN6068LK3 above -  https://www.mouser.com/ProductDetail/Diodes-Incorporated/ZXMP6A16KTC?qs=7EMYER6HMn3fGPb2RALoHA%3D%3D

4.Finally, for my last few builds I have cascaded the logic power section instead of tying each linear regulator to DC input (~22v). I guess it comes down to causing more heating in the main 20v regulator and less in the 9v and 5v. With this method I haven't noticed excessive heating in the first regulator. I also have small SMD heatsinks I can also stick on if I need to help dissipate heat. Is there a 'right' way to do it?

Thanks,
Zak


« Last Edit: January 07, 2024, 09:47:08 AM by ZakW »

Offline ZakW

  • High Voltage Technician
  • ***
  • Posts: 179
  • Karma: +6/-0
  • YouTube @QZW_Labs
    • View Profile
Re: RDRSSTC - Project Build
« Reply #9 on: December 28, 2023, 08:34:05 PM »
Quote
1. Half wave vs full wave rectification for the bridge - I used a single diode in my RSSTC for halfwave rectification for the bridge. It was a SMD 600v 10A 200A peak standard diode, never had any failures with it. Since this is a Ramped DRSSTC currents should be much higher. My assumption is that a full bridge part/package would be better suited to handle the power and heat dissipation, could I also get away with using a beefier single diode instead? Although, I never did have a heating issue with using a single diode in my RSSTC. I am not sure which solution is better.
       - If I use a full bridge but my ZCD is only half wave rectification via a single 1N4148, would their be an issue with the bridge being powered from both cycles instead of just the half cycles like with a single diode? The ZCD wont trigger and power the
               bridge on for all cycles since it is only outputting a signal on the positive half cycle, which is fine. I only run the interrupter at low BPS, I don't care much for higher BPS.
Going to just use the same single diode and I will see how it goes.

Quote
2. I am aiming for as little bridge inductance as possible but I would still like to include TVS diodes across CE. Are two 1.5kW 220V in series better or can I get away with a single diode 1.5kW 400v type for each?
       - 220v https://www.mouser.com/ProductDetail/652-1.5SMC220CA
       - 400v https://www.mouser.com/ProductDetail/576-1.5SMC400CA
Looks like others have used a single 400v TVS. I will do the same.

Quote
3.Since I am trying to simplify the design a bit I really just added the phase adjust to the UD 1.3b. However, the push/pull transistor stage parts after the UCC27423 are outdated. I have seen other use IRF530/IRF9530, 100v 17A parts but I don't think I need such highly rated MOSFETs. Plus they have much high Qg compared to lower voltage parts. While I have found other parts with better characteristics https://www.mouser.com/ProductDetail/Diodes-Incorporated/DMN6068LK3-13?qs=4YT44p7w2bsq47X783VrzA%3D%3D it is hard to find if they have a PNP counterpart, like the IRF530 vs the IRF9530. Does anyone know of a way to identify a close alternative for a complimentary NPN/PNP stage?
       - Most PNP parts I have found differ slightly, is this expected and still usable or should Vdss and Id match a close as possible?
       - Example of something that might match the PNP DMN6068LK3 above -  https://www.mouser.com/ProductDetail/Diodes-Incorporated/ZXMP6A16KTC?qs=7EMYER6HMn3fGPb2RALoHA%3D%3D
Sounds like the IRF530 vs the IRF9530 pair work well. I might try and find complimentary parts with similar but better characteristics if possible.

Quote
4.Finally, for my last few builds I have cascaded the logic power section instead of tying each linear regulator to DC input (~22v). I guess it comes down to causing more heating in the main 20v regulator and less in the 9v and 5v. With this method I haven't noticed excessive heating in the first regulator. I also have small SMD heatsinks I can also stick on if I need to help dissipate heat. Is their a 'right' way to do it?
I am just going to cascade the regulators and add a small SMD heatsink to the 20v regulator if needed.



Finished my first pass on the UD 1.3b with added phase lead. I incorporated the staccato interrupter onto the same PCB. Finally, I redesigned the full bridge layout to be similar to Loneoceans easy bridge setup. IGBTs will lay flat and mount to the top of the heatsink.

Here are my designs so far. Feedback would be appreciated. I still need to go through my schematic a few extra times to ensure I did not make a mistake.



















-Zak




Offline davekni

  • Executive Board Member
  • *******
  • Posts: 2680
  • Karma: +127/-1
  • Physicist, engineer (electronic), and hobbiest
    • View Profile
Re: RDRSSTC - Project Build
« Reply #10 on: December 28, 2023, 09:16:47 PM »
Generally looks good.  You may want to add tape where IGBT leads cross other planes.  Solder mask by itself may be good enough, but not reliable at high voltages.

If you want to use higher current bridge rectifier, use it as a single diode.  Two bridge diodes can be paralleled to double current.  Wire bridge's two AC terminals together.  Use that and either + or - output (but not both) as the two diode leads.
David Knierim

Offline ZakW

  • High Voltage Technician
  • ***
  • Posts: 179
  • Karma: +6/-0
  • YouTube @QZW_Labs
    • View Profile
Re: RDRSSTC - Project Build
« Reply #11 on: December 28, 2023, 09:33:53 PM »
Quote
Generally looks good.  You may want to add tape where IGBT leads cross other planes.  Solder mask by itself may be good enough, but not reliable at high voltages.
Thanks, Dave. The IGBTs will be mounted either above or below the PCB (limitation of the 3d model) so the leads will be curved to allow some clearance from the PCB. 

Quote
If you want to use higher current bridge rectifier, use it as a single diode.  Two bridge diodes can be paralleled to double current.  Wire bridge's two AC terminals together.  Use that and either + or - output (but not both) as the two diode leads.
There isn't really enough room for a full bridge, worse case I could also stack two single diodes on one another to increase current capabilities. I did also find higher current diodes in the same package so I am not too worried.
« Last Edit: January 07, 2024, 09:45:50 AM by ZakW »

Offline ZakW

  • High Voltage Technician
  • ***
  • Posts: 179
  • Karma: +6/-0
  • YouTube @QZW_Labs
    • View Profile
Re: RDRSSTC - Project Build
« Reply #12 on: January 07, 2024, 02:50:26 AM »
Alright, modified UD 1.3b is assembled and so is the new bridge. I have been working like a mad man the last couple of days on this.









Nailed the 3D printed clamp first try. Printed with 100% infill and seems plenty rigid, doesn't flex as far as I can tell. Had to redo the heatsink and ended up making the IGBT leads/spacing a little bit too long but I already have a couple things I want to change anyway.



Testing and first issue:

Powered up the driver with the GDT connected to the full bridge. Signal generator connected to + pin of the CT feedback, running at 400kHz. At 25v it draws around 0.11A, nothing gets hot. Onboard interrupter is working. The damn OCD LED is stuck on though...I have tried adjusting the variable 10k pot but I cant seem to get it to turn off.

Any ideas as to why it would be on as soon as it is powered up? I am not supplying any power to the full bridge yet. Retracing the 1.3b driver so far, I have matched the sections exactly in my schematic. I will continue probing around to see if I can figure anything out in the mean time. I am just not very familiar with this driver at all.

EDIT: Fixed the issue. Turns out I was missing a ground connection for the OCD feedback input section. Soldered a small jumper and the light is off now! I will start testing other parts of the driver now that everything isn't disabled.


Thanks!



Alright, not out of the woods yet. I think I made a mistake in my PCB. Here are the schematics I referenced, 1.3b and 2.1c



Links to both:
1.3b - https://kaizerpowerelectronics.dk/files/stevehv.4hv.org_files/universal_driver_1.3b/DRSSTC_pndriver1_3b.pdf
2.1b - https://kaizerpowerelectronics.dk/files/stevehv.4hv.org_files/universal_driver_2.1b/UD2_1revbschem.pdf

When I was looking at how I was going to add phase lead into the 1.3b schematic I excluded the 74hc14 inverting stage, circled in red in the 1.3b schematic. Looking at the 2.1b there is an extra inverting stage, also circled in red. I added all of the highlighted section in 2.1b nothing else. Scoping the output of my driver it looks like it is constantly running and stops only when the interrupter pulses, which is the opposite of what it should be doing. Seems like the missing inverting stage is the cause.

Here is my schematic for reference:



I would really appreciate if someone would be willing to take a look and confirm my error.

If I did miss a stage I might be able to cut some traces and use jumper wires to at least correct the issue and test the board. I can then work on fixing the issues and eventually ordering another one.


« Last Edit: January 07, 2024, 09:45:27 AM by ZakW »

Offline davekni

  • Executive Board Member
  • *******
  • Posts: 2680
  • Karma: +127/-1
  • Physicist, engineer (electronic), and hobbiest
    • View Profile
Re: RDRSSTC - Project Build
« Reply #13 on: January 07, 2024, 04:20:51 AM »
Quote
Nailed the 3D printed clamp first try. Printed with 100% infill and seems plenty rigid, doesn't flex as far as I can tell. Had to redo the heatsink and ended up making the IGBT leads/spacing a little bit too long but I already have a couple things I want to change anyway.
Clamps look great!
Yes, lead spacing is long and likely to cause problems.  I'd mount IGBT bodies up against ECB edges to get leads as short as possible.  Given ECB layout, leads can't be as short as would be ideal (ie. with pads at ECB edges).

Quote
Fixed the issue. Turns out I was missing a ground connection for the OCD feedback input section. Soldered a small jumper and the light is off now! I will start testing other parts of the driver now that everything isn't disabled.
Ground should be as close to a solid copper plane as possible.  If a section is floating, I'd connect it with several wires at different locations to be a closer approximation to a ground plane.

Overall looks like great progress.
David Knierim

Offline AstRii

  • High Voltage Engineer
  • ****
  • Posts: 255
  • Karma: +7/-0
  • Czech Technical University in Prague
    • View Profile
    • UHVlab - Tesla Coils | High Voltage | Education
Re: RDRSSTC - Project Build
« Reply #14 on: January 07, 2024, 04:21:41 AM »
What is the purpose of the 3D printed clamp? You could mount the transistors directly to the heatsink. That extra metal pad between IGBT and thermal pad also seems unnecessary. It's all adding high thermal resistance and so the cooling will be worse.
I also believe a thermal pad on its own is not good enough, it should be used in combination with thermal paste (maybe I'm wrong on this?)
Bc. Marek Novotny
Czech Republic, Czech Technical University in Prague
www.uhvlab.org

Offline ZakW

  • High Voltage Technician
  • ***
  • Posts: 179
  • Karma: +6/-0
  • YouTube @QZW_Labs
    • View Profile
Re: RDRSSTC - Project Build
« Reply #15 on: January 07, 2024, 04:30:01 AM »
Thanks, Dave! Looks like I missed your response while I was editing my last post with another issue.

Quote
Yes, lead spacing is long and likely to cause problems.  I'd mount IGBT bodies up against ECB edges to get leads as short as possible.  Given ECB layout, leads can't be as short as would be ideal (ie. with pads at ECB edges).
Quote
Ground should be as close to a solid copper plane as possible.  If a section is floating, I'd connect it with several wires at different locations to be a closer approximation to a ground plane.
Noted, I will make these changes to the next version.

Quote
What is the purpose of the 3D printed clamp? You could mount the transistors directly to the heatsink. That extra metal pad between IGBT and thermal pad also seems unnecessary. It's all adding high thermal resistance and so the cooling will be worse.
I also believe a thermal pad on its own is not good enough, it should be used in combination with thermal paste (maybe I'm wrong on this?)
The clamps are better for distributing the force of the mounting screw to the body of the IGBT or MOSFET for increased thermal transfer. The screw, if too tight, can cause the IGBT to even lift a bit too. The small aluminum pieces are there for thermal mass to absorb rapid spikes in temperature due to the ramped nature of the coil, the heat is then more slowly distributed to the larger heatsink. I do have thermal paste on the IGBT to the aluminum pieces.
« Last Edit: January 07, 2024, 09:47:27 AM by ZakW »

Offline davekni

  • Executive Board Member
  • *******
  • Posts: 2680
  • Karma: +127/-1
  • Physicist, engineer (electronic), and hobbiest
    • View Profile
Re: RDRSSTC - Project Build
« Reply #16 on: January 07, 2024, 04:51:55 AM »
Quote
The small aluminum pieces are their for thermal mass to absorb rapid spikes in temperature due to the ramped nature of the coil, the heat is then more slowly distributed to the larger heatsink. I do have thermal paste on the IGBT to the aluminum pieces.
Thought about suggesting this on my previous reply:  The "small" aluminum pieces would be better if larger, and even better yet if copper.  If necessary to shorten leads, they could be thicker.  Thickness is a trade-off.  Increases thermal mass and reduces thermal spreading resistance, but does also increase vertical thermal resistance a bit.  Overall I'd guess somewhat thicker would be net benefit for thermals besides allowing shorter leads.  Larger area would make the most improvement.
Are your thermal pads compliant?  If rigid such as mica or ceramic, then thermal paste is needed on each side of pads too.

Quote
Looking at the 2.1b their is an extra inverting stage, also circled in red. I added all of the highlighted section in 2.1b nothing else. Scoping the output of my driver it looks like it is constantly running and stops only when the interrupter pulses, which is the opposite of what it should be doing. Seems like the missing inverting stage is the cause.
That "also circled in red" inverter appears to be a limit on maximum on-time and duty cycle.  Would cause trouble for a coil running 5ms on-time.  Sounds like you have another inversion mistake somewhere, perhaps a FF Q instead of QN output or such.  I have a hard time following schematics drawn without normal FF and gate symbols, so not sure where your inversion error is.  (BTW, I moved to KiCad from DesignSpark largely because KiCad has better symbols available.)
David Knierim

Offline ZakW

  • High Voltage Technician
  • ***
  • Posts: 179
  • Karma: +6/-0
  • YouTube @QZW_Labs
    • View Profile
Re: RDRSSTC - Project Build
« Reply #17 on: January 07, 2024, 05:13:51 AM »
Quote
Thought about suggesting this on my previous reply:  The "small" aluminum pieces would be better if larger, and even better yet if copper.  If necessary to shorten leads, they could be thicker.  Thickness is a trade-off.  Increases thermal mass and reduces thermal spreading resistance, but does also increase vertical thermal resistance a bit.  Overall I'd guess somewhat thicker would be net benefit for thermals besides allowing shorter leads.  Larger area would make the most improvement.
Tried using what I had on hand. If it gets too hot I can always add thicker aluminum.

Quote
Are your thermal pads compliant?  If rigid such as mica or ceramic, then thermal paste is needed on each side of pads too.
I am using soft silicone pad material.

Quote
That "also circled in red" inverter appears to be a limit on maximum on-time and duty cycle.  Would cause trouble for a coil running 5ms on-time.  Sounds like you have another inversion mistake somewhere, perhaps a FF Q instead of QN output or such.  I have a hard time following schematics drawn without normal FF and gate symbols, so not sure where your inversion error is.  (BTW, I moved to KiCad from DesignSpark largely because KiCad has better symbols available.)
I use KiCad as well. I have a plug in that I use to download footprints and 3D models directly from Mouser, it is really useful and streamlined. Download the file and it auto adds it to the library.

I will look through my schematic some more tomorrow. Been working on this for about 9 hours straight today.

Update:

Using my function generator I input a 200kHz signal into the CT input and measured the interrupter output as well as the driver output. Confirmed that the coil is running until the interrupter signal starts which is backwards.

Yellow = GDT output
Purple = Interrupter output







« Last Edit: January 07, 2024, 07:27:17 AM by ZakW »

Offline flyingperson23

  • High Voltage Technician
  • ***
  • Posts: 107
  • Karma: +5/-2
  • noob :)
    • View Profile
Re: RDRSSTC - Project Build
« Reply #18 on: January 07, 2024, 03:59:49 PM »
The small aluminum pieces look very close to the heatsink and are electrically connected to the igbt. Maybe make the thermal pad a little bigger than the aluminum on all sides so it doesn't arc over like in https://highvoltageforum.net/index.php?topic=2643.0

Offline ZakW

  • High Voltage Technician
  • ***
  • Posts: 179
  • Karma: +6/-0
  • YouTube @QZW_Labs
    • View Profile
Re: RDRSSTC - Project Build
« Reply #19 on: January 08, 2024, 01:34:00 AM »
Quote
The small aluminum pieces look very close to the heatsink and are electrically connected to the igbt. Maybe make the thermal pad a little bigger than the aluminum on all sides so it doesn't arc over like in https://highvoltageforum.net/index.php?topic=2643.0
Good call, thanks for pointing that out. Better safe than sorry. The pack of sheets I have come in varying thicknesses I will get a thicker sheet with more clearance.

Offline ZakW

  • High Voltage Technician
  • ***
  • Posts: 179
  • Karma: +6/-0
  • YouTube @QZW_Labs
    • View Profile
Re: RDRSSTC - Project Build
« Reply #20 on: January 08, 2024, 02:25:29 AM »
Fixed the output, the driver appears to be switching correctly now. Got a crash course on the logic used and followed it to the driver IC. I used an non invert/invert instead of a dual inverting driver IC. Must have mixed up that parts along the way and installed the wrong IC.

Looking at the bridge now!

Update:using my signal generator I was able to get a small breakout at 400kHz using my variac. The coil seems to be running CW and is not being interrupted. Still looking into it.

Quote
That "also circled in red" inverter appears to be a limit on maximum on-time and duty cycle.  Would cause trouble for a coil running 5ms on-time.
Can you explain a bit more about this? I don't see the equivalent in the 1.3 driver.
« Last Edit: January 08, 2024, 03:33:01 AM by ZakW »

Offline davekni

  • Executive Board Member
  • *******
  • Posts: 2680
  • Karma: +127/-1
  • Physicist, engineer (electronic), and hobbiest
    • View Profile
Re: RDRSSTC - Project Build
« Reply #21 on: January 08, 2024, 04:22:12 AM »
Quote
Can you explain a bit more about this? I don't see the equivalent in the 1.3 driver.
The R/C network on the inverter input is a delay that monitors enable signal.  If on too long, the inverter input goes high, output low, which removes enable.  After a longer off-time delay, inverter output goes back high, allowing enable to pass through the AND gate again.  This helps prevent coil burn-out if enable is accidentally stuck on or set to too-high a duty cycle.  That feature appears to have been added after UD1.3.
David Knierim

Offline ZakW

  • High Voltage Technician
  • ***
  • Posts: 179
  • Karma: +6/-0
  • YouTube @QZW_Labs
    • View Profile
Re: RDRSSTC - Project Build
« Reply #22 on: January 08, 2024, 05:03:07 AM »
Quote
The R/C network on the inverter input is a delay that monitors enable signal.  If on too long, the inverter input goes high, output low, which removes enable.  After a longer off-time delay, inverter output goes back high, allowing enable to pass through the AND gate again.  This helps prevent coil burn-out if enable is accidentally stuck on or set to too-high a duty cycle.  That feature appears to have been added after UD1.3.
Thanks for the clarification.

So after scouring post after post it sounded like the typical fiber connector inverts the interrupter signal. I cut the trace from pin 2 of the 74hc14 and wired it directly to pin 3 of the 74hc74 and it is working!!! The driver only runs during the interrupter pulse, current consumption is way lower (of course). Now I just cant get it to work off of CT feedback.

I can get it to work using my signal generator but that is it. Using a 400kHz signal I am getting about 3in arcs. I tried flipping the phase but scoping the bridge and driver I am not seeing the coil trying to oscillate.

First core (white wire) has 1 turn through both blue and green wire cores. 32 turns on all cores.



Update: Right now I am just trying to get the primary to oscillate so I removed the secondary. I have a chunk of metal inside the primary to absorb some energy.

Primary: 7 turns or 18awg wire, 6.8nF cap. JavaTC says it should oscillate around 877kHz. That is about twice as high as I want so I will try increasing the capacitance to 20nF, that should get me to 511kHz. Still though, I should be seeing the primary oscillate even if it is around 880kHz, right?

I also tested at what voltage is too low for using the signal generator as feedback. Anything under 2v and the output of the driver becomes unstable, cutting out completely at around 1.3v. I rewound a new CT using 2 N87 cores with 22T on each for ~500:1. Flipped phasing around, still cannot get it to oscillate on its own.


Update #2: Referencing Dave's suggestion here - https://highvoltageforum.net/index.php?topic=1373.msg10197#msg10197
Quote
My favorite way to fix startup issues is to make the driver self-oscillating near the coil's resonant frequency.  That can be done to UD2.7 by adding a ~50k resistor from positive comparitor output (IC8 pin 7) to its inverting input (IC8 pin 3), removing R7, and adjusting the value of C33 to get a reasonable frequency.  This works only when jumper SV1 is inserted.  Adding the 50k resistor may be easier soldering by using the open pad for R7 as a connection to IC8-7 and and one end of D1, D2, or R2 for a connection to IC8-3.

50k did not work for me though. I added a 100k pot and tried different values. I still need to measure the resistance but at a certain point I can get the driver to oscillate and subsequently the primary does as well. This is with CT feedback. I added the secondary in there to see if I could get any output. The variac was thumping hard, I tried removing the ferrite rod from my DIY inductor and the thumping was less loud, however when I removed the jumper (no phase lead) the coil came alive! I referenced Loneoceans suggested inductor size but I likely need to fine tune it.

So it seems to be working with self-oscillation as well as no phase lead.

Update #3: Correction, it is working intermittently with phase lead. The self oscillation seems unstable and very finicky. I also switched to a larger secondary I had on hand. I was using one of my mini 2in coils but the larger coil is easier to test on. Managed to get ~10in arcs at around 75v but they were not very straight.

New coil Fres (unloaded) is 500kHz.

JavaTC says 5 turns @ 20nF should put me around 457kHz with 0.324 coupling.
 
« Last Edit: January 09, 2024, 05:31:42 AM by ZakW »

Offline davekni

  • Executive Board Member
  • *******
  • Posts: 2680
  • Karma: +127/-1
  • Physicist, engineer (electronic), and hobbiest
    • View Profile
Re: RDRSSTC - Project Build
« Reply #23 on: January 09, 2024, 05:38:07 AM »
Quote
I cut the trace from pin 2 of the 74hc14 and wired it directly to pin 3 of the 74hc74 and it is working!!!
I'm not quite following this mod, but if you are bypassing an HC14 stage, you may be missing out on HC14 hysteresis.  Slow rise and/or fall times from optical receiver may trigger subsequent logic at different voltages and therefore different times if not cleaned up by HC14 hysteresis.  Generally best to add an extra stage of HC14 inversion rather than removing one.  Though I'm not certain exactly whether your mod has this issue or not.  Obviously working for now.  Just a risk of possible issues in the future.

Quote
50k did not work for me though. I added a 100k pot and tried different values. I still need to measure the resistance but at a certain point I can get the driver to oscillate and subsequently the primary does as well. This is with CT feedback. I added the secondary in there to see if I could get any output. The variac was thumping hard, I tried removing the ferrite rod from my DIY inductor and the thumping was less loud, however when I removed the jumper (no phase lead) the coil came alive! I referenced Loneoceans suggested inductor size but I likely need to fine tune it.
You may need to decrease size of C6 to get your relatively high frequency with a reasonable self-oscillation feedback resistor value.
BTW, QCW and ramped coils are particularly prone to startup problems, since bus voltage is low when oscillation needs to start.  QCW coils often use FPGAs or other logic to force some number of startup cycles, or use a PLL to have oscillation running prior to feedback being sufficient.  My self-oscillation modification is an alternative, one I use in my QCW coil.
David Knierim

Offline ZakW

  • High Voltage Technician
  • ***
  • Posts: 179
  • Karma: +6/-0
  • YouTube @QZW_Labs
    • View Profile
Re: RDRSSTC - Project Build
« Reply #24 on: January 10, 2024, 06:16:43 AM »
Quote
I'm not quite following this mod, but if you are bypassing an HC14 stage, you may be missing out on HC14 hysteresis.  Slow rise and/or fall times from optical receiver may trigger subsequent logic at different voltages and therefore different times if not cleaned up by HC14 hysteresis.  Generally best to add an extra stage of HC14 inversion rather than removing one.  Though I'm not certain exactly whether your mod has this issue or not.  Obviously working for now.  Just a risk of possible issues in the future.
I skipped IC1F pins 5 & 6 and wired my interrupter directly to pin 1 of IC2A (74HC08). My signal was being inverted one too many times, that seemed to have fixed the issue. Might not be the best solution but at least it got it working for now.



Quote
You may need to decrease size of C6 to get your relatively high frequency with a reasonable self-oscillation feedback resistor value.
BTW, QCW and ramped coils are particularly prone to startup problems, since bus voltage is low when oscillation needs to start.  QCW coils often use FPGAs or other logic to force some number of startup cycles, or use a PLL to have oscillation running prior to feedback being sufficient.  My self-oscillation modification is an alternative, one I use in my QCW coil.
I tried adjusting this but I cant seem to get consistent results. Tuning this does impact the look and sound of the arcs, sort of like my previous coil. Once adjusted correctly the popping and snapping is minimal.

Speaking of which, I cant seem to get good sword arcs with a topload attached. I took a short video and some scope captures. My secondary Fres is 500kHz unloaded so my primary is still out of tune at around 550kHz. I know the topload is lowering the Fres even more but is that why the arc sounds snappy and loud? In the pictures below you can see the blue trace (bridge output) how the sword arcs make a really uniform smooth output but when the arcs are snapping it is more trumpet shape.


Blue = Bridge output
Yellow = TL3116 output (pin 7)
purple = CT feedback (SV1 jumper)

No topload



Blue = Vge


Notice how this waveform is uniform compared to when a topload is used.


Blue= bridge output



Topload on






Do the 'no topload' waveforms look alright? I haven't tried tuning phase lead yet.

« Last Edit: January 10, 2024, 07:47:37 AM by ZakW »

Offline davekni

  • Executive Board Member
  • *******
  • Posts: 2680
  • Karma: +127/-1
  • Physicist, engineer (electronic), and hobbiest
    • View Profile
Re: RDRSSTC - Project Build
« Reply #25 on: January 11, 2024, 05:05:06 AM »
Quote
I skipped IC1F pins 5 & 6 and wired my interrupter directly to pin 1 of IC2A (74HC08). My signal was being inverted one too many times, that seemed to have fixed the issue. Might not be the best solution but at least it got it working for now.
Yes, not the best solution.  Missing hysteresis of HC14.  Would be better to patch in the spare HC14 instead.  Might stay working fine as is.  I haven't analyzed in detail what issues could be caused by this specific circuit missing hysteresis.

Quote
purple = CT feedback (SV1 jumper)
Triangle-wave shape looks like running in SSTC mode rather than DRSSTC.  Would expect closer to a sine wave.  Even SSTCs with reasonable coupling factor look more sine wave like than your captures, which are all triangle-wave shaped.  Is MMC way too large or perhaps failed shorted?

Quote
Speaking of which, I cant seem to get good sword arcs with a topload attached. I took a short video and some scope captures.
I think the issue is too short a breakout on top of the top load.  Top load shields breakout tip, reducing electric field at tip.  Takes higher secondary voltage before breakout starts.  Breakout is already well up line quarter-cycle ramp.  Once breakout occurs, voltage is high enough to make arc grow too fast for sword sparks, fast like normal DRSSTC arcs.

Quote
My secondary Fres is 500kHz unloaded so my primary is still out of tune at around 550kHz. I know the topload is lowering the Fres even more but is that why the arc sounds snappy and loud?
Even farther out of tune may contribute to arc behavior.  However, QCW coils (and I presume RDRSSTC coils too) work best operating at upper pole.  Two ways to get upper-pole operation.  One is to keep primary frequency a bit above secondary (unlike normal DRSSTC tuning).  Other is to have pre-startup oscillation at a higher frequency (upper pole frequency).  Latter approach works only if coupling is high enough and secondary frequency is not too far above primary frequency.
David Knierim

Offline ZakW

  • High Voltage Technician
  • ***
  • Posts: 179
  • Karma: +6/-0
  • YouTube @QZW_Labs
    • View Profile
Re: RDRSSTC - Project Build
« Reply #26 on: January 11, 2024, 06:02:41 PM »
Quote
Yes, not the best solution.  Missing hysteresis of HC14.  Would be better to patch in the spare HC14 instead.  Might stay working fine as is.  I haven't analyzed in detail what issues could be caused by this specific circuit missing hysteresis.
I will make an update to my schematic and PCB file to include an extra stage.

Quote
Triangle-wave shape looks like running in SSTC mode rather than DRSSTC.  Would expect closer to a sine wave.  Even SSTCs with reasonable coupling factor look more sine wave like than your captures, which are all triangle-wave shaped.  Is MMC way too large or perhaps failed shorted?
I am having issues getting the coil to run at different frequencies. It seems to always oscillate much higher than what javaTC predicts, I know it is just an estimation but I cannot seem to change the frequency much regardless of MMC value or primary. It tends to always be around 500kHz even though I aim for 400kHz or a little lower.

I did notice that after increasing coupling, changing the MMC amount and turn count the feedback signal (purple) was a lot more sinusoidal.

Quote
I think the issue is too short a breakout on top of the top load.  Top load shields breakout tip, reducing electric field at tip.  Takes higher secondary voltage before breakout starts.  Breakout is already well up line quarter-cycle ramp.  Once breakout occurs, voltage is high enough to make arc grow too fast for sword sparks, fast like normal DRSSTC arcs.
You were right, I increased the length and the snapping went away!  ;D

Quote
Even farther out of tune may contribute to arc behavior.  However, QCW coils (and I presume RDRSSTC coils too) work best operating at upper pole.  Two ways to get upper-pole operation.  One is to keep primary frequency a bit above secondary (unlike normal DRSSTC tuning).  Other is to have pre-startup oscillation at a higher frequency (upper pole frequency).  Latter approach works only if coupling is high enough and secondary frequency is not too far above primary frequency.
Sounds good, I have been reading as much as I can about tuning.

Question regarding checking secondary and primary tuning with a signal generator. I found this video https://www.youtube.com/watch?v=GLyW1zRZymk and they show this diagram for how everything is all connected:



Is that correct? I always see the MMC in series with the primary unlike the diagram. I followed the diagram and was able to find the resonant frequency of my current MMC & primary as well as the secondary with a 20in wire to simulate loading. Secondary with topload and wire was 360kHz and the primary was 310kHz  but again when I ran the coil it was quite a bit higher than what was measured. I am at a loss for this.

Edit: I see your post here https://highvoltageforum.net/index.php?topic=783.msg5109#msg5109
Quote
What values do you have for L1, C32, and C33?  Also, what IGBTs are being used?
I am using the standard values per the schematic, 150nF 150pF for C32 and 220pF for C33. What impact does adjusting C32 have?
Quote
2) C33 should be a bit lower for your relatively-high frequency operation of 280kHz.  I'd suggest 470pF, or 680pF at most.
Per Loneoceans notes, I think 220pF for C33 is correct. Ideally I want to operate somewhere in the range of 350-450kHz, depending on the secondary used. I am using a place holder until I get everything running correctly.

Update: Seems like it is the phase adjustment portion of the driver that is causing the issues, copied from the 2.1b and added to 1.3b. When the SV1 jumper is in place the primary fres is around 555kHz, hardly changes with added capacitance. If I remove the jumper fres drops to ~320kHz and responds when MMC is adjusted.
« Last Edit: January 12, 2024, 05:53:15 AM by ZakW »

Offline davekni

  • Executive Board Member
  • *******
  • Posts: 2680
  • Karma: +127/-1
  • Physicist, engineer (electronic), and hobbiest
    • View Profile
Re: RDRSSTC - Project Build
« Reply #27 on: January 12, 2024, 05:05:30 AM »
Quote
I did notice that after increasing coupling, changing the MMC amount and turn count the feedback signal (purple) was a lot more sinusoidal.
Good, sounds like progress.

Quote
Is that correct? I always see the MMC in series with the primary unlike the diagram. I followed the diagram and was able to find the resonant frequency of my current MMC & primary as well as the secondary with a 20in wire to simulate loading. Secondary with topload and wire was 360kHz and the primary was 310kHz  but again when I ran the coil it was quite a bit higher than what was measured. I am at a loss for this.
That video is measuring frequency of a parallel-resonant circuit, seeing where impedance peaks (maximum impedance frequency).  If measuring series resonant, drive impedance will be minimum at resonance.  Either works for primary.  However, was secondary removed for primary measurement?  Presence of secondary changes primary frequency due to coupling.  For secondary, series resonant mode is the only reasonable way to check.  Any connection to top will change capacitance.  For measuring secondary, it can be in place, but primary coil must be open-circuit to not affect secondary.
Any pair of coupled resonant circuits has two resonant frequencies, neither of which are same as individual frequencies.  Upper pole and lower pole frequencies.  Most QCW and ramped DRSSTC coils run at upper pole frequency.  You can measure those two frequencies by measuring with both coils in place, secondary bottom grounded, and MMC connected.

Quote
I am using the standard values per the schematic, 150nF for C32 and 220pF for C33. What impact does adjusting C32 have?
C32 is a small cap just to filter out any high-frequency noise (such as coupled from bridge output switching events) that might cause unintended comparitor switching.  Presuming we are looking at the same schematic, C32 is the capacitor across CT secondary.  Value is usually 150pF.  If you are using 150nF that could explain problems!  C33 value of 220pF should be good for your frequencies.

Quote
When the SV1 jumper is in place the primary fres is around 555kHz, hardly changes with added capacitance. If I remove the jumper fres drops to ~320kHz and responds when MMC is adjusted.
Operating with SV1 removed is likely to damage circuitry with excess CT output voltage.  I'd check R2 to see if it is still 1k.  Although if you really have 150nF for C32, that would avoid the damage, providing sufficient load to CT output.
« Last Edit: January 12, 2024, 05:07:01 AM by davekni »
David Knierim

Offline ZakW

  • High Voltage Technician
  • ***
  • Posts: 179
  • Karma: +6/-0
  • YouTube @QZW_Labs
    • View Profile
Re: RDRSSTC - Project Build
« Reply #28 on: January 12, 2024, 06:36:33 AM »
Quote
Good, sounds like progress.
Maybe a little, but tuning it today was frustrating.

Quote
That video is measuring frequency of a parallel-resonant circuit, seeing where impedance peaks (maximum impedance frequency).  If measuring series resonant, drive impedance will be minimum at resonance.  Either works for primary.
Thanks for the clarification. If I understand you correctly, I can have the MMC series or parallel? Are there any benefits or drawback to either configuration? When I google DRSSTC schematics I only see MMC in series with the primary.

Quote
However, was secondary removed for primary measurement?  Presence of secondary changes primary frequency due to coupling.  For secondary, series resonant mode is the only reasonable way to check.  Any connection to top will change capacitance.  For measuring secondary, it can be in place, but primary coil must be open-circuit to not affect secondary.
I took several measurements today and noted all of the values. I also measured under different configurations: with and without primary in place, different toploads, finally a 20in wire to simulate arc.

For the secondary testing I just connect my signal gen to the base and hang a probe near by. Tested various size toploads and noted the Fres.

For the primary I set it up like the schematic suggested so I guess I was measuring parallel-resonance instead. I took measurements with and without the primary around the secondary. Another thing I noticed was the impact of grounding the secondary. I wasn't sure which was correct so I noted those values as well. Grounding the secondary made the Fres quite a bit lower.

Quote
primary coil must be open-circuit
As in not being connected to the MMC?

Quote
Any pair of coupled resonant circuits has two resonant frequencies, neither of which are same as individual frequencies.  Upper pole and lower pole frequencies.  Most QCW and ramped DRSSTC coils run at upper pole frequency.  You can measure those two frequencies by measuring with both coils in place, secondary bottom grounded, and MMC connected.
So if I know the Fres of the secondary is say 500kHz but when the primary is in place and the MMC is connected (secondary is grounded) I can remeasure and determine the upper pole and lower pole? Will the Fres peak higher than 500kHz for upper and the same for a Fres below 500kHz for lower? I was reading Loneoceans DRSSTC and QCW pages but he never explained how he took these measurements.

Quote
C32 is a small cap just to filter out any high-frequency noise (such as coupled from bridge output switching events) that might cause unintended comparitor switching.  Presuming we are looking at the same schematic, C32 is the capacitor across CT secondary.  Value is usually 150pF.  If you are using 150nF that could explain problems!  C33 value of 220pF should be good for your frequencies.
That was a typo  :( I updated my post to correct it. I did install a 150pF cap like the schematic suggests.

Quote
Operating with SV1 removed is likely to damage circuitry with excess CT output voltage.  I'd check R2 to see if it is still 1k.  Although if you really have 150nF for C32, that would avoid the damage, providing sufficient load to CT output.
I did notice without SV1 that feedback voltage was high, I think around 6.4V at times. I only removed it out of frustration. I will check R2 to verify its value and run it with the jumper installed going forward.

Final note on testing: I am using a multi turn primary with 8 turns. I have several caps soldered in place to be able to easily add and remove them. I use two 10nF caps as well as several small 6.8nF for smaller increments. I measured the primary Fres which came out to 310kHz but when the coil was running , bridge output and feedback both showed it running over 500kHz... what could cause this? The secondary Fres without a topload was 530kHz, with a topload and 20in wire, it dropped to 360kHz. So the primary seems to be running far off from resonance.

Sometimes I get what looks like a good primary tap & MMC but then OCD trips at or near120v. So I make a slight adjustment but then OCD trips at a much lower voltage. If it doesn't trip then the arcs are loud, snappy and branched.  >:( 

How might I assume a safe primary current for my IGBTs? I know Loneoceans has a section on how OCD CT voltage correlates to current and how to adjust that voltage via R10 but I am wondering how you can assume this part can run a 250A or 500A? I can double check the datasheet if the answer is there but I assumed since the IGBTs are being driven harder we assume they can handle higher peak currents.

Offline davekni

  • Executive Board Member
  • *******
  • Posts: 2680
  • Karma: +127/-1
  • Physicist, engineer (electronic), and hobbiest
    • View Profile
Re: RDRSSTC - Project Build
« Reply #29 on: January 13, 2024, 07:38:18 PM »
Quote
Thanks for the clarification. If I understand you correctly, I can have the MMC series or parallel? Are there any benefits or drawback to either configuration? When I google DRSSTC schematics I only see MMC in series with the primary.
Any given inductor and capacitor together can form a resonant circuit.  Frequency is the same whether driven in series or parallel.  Most DRSSTC primaries are driven in parallel.  (Only exception I'm aware of is ZVS driven coils.)  Measuring primary frequency can be done in parallel or series configuration.  Doesn't matter.  Frequency is the same.

Quote
As in not being connected to the MMC?
OK to have one primary lead connected to MMC as long as other lead is open or other side of MMC is open.  Just avoid any closed circuit on primary.  Break that closed circuit at any one point, where ever is convenient.

Quote
So if I know the Fres of the secondary is say 500kHz but when the primary is in place and the MMC is connected (secondary is grounded) I can remeasure and determine the upper pole and lower pole? Will the Fres peak higher than 500kHz for upper and the same for a Fres below 500kHz for lower? I was reading Loneoceans DRSSTC and QCW pages but he never explained how he took these measurements.
Yes for the two pole frequencies.  Probably easiest to measure the assembled system through the primary.  Have secondary in place, bottom grounded and top to top load (and arc simulation wire if you want loaded frequencies).  Then measure frequencies the same way you measured the single isolated primary frequency.

Quote
I did notice without SV1 that feedback voltage was high, I think around 6.4V at times. I only removed it out of frustration. I will check R2 to verify its value and run it with the jumper installed going forward.
SV1 can be installed in either position (with or without phase lead), just not left open.  UD2.7 CT (SV1) voltages are intended to be high, often peak at 50 to 100V.  Without SV1 installed, voltage can go even higher, so fry resistors.  However, in your case, perhaps CT secondary current is too low for reliable US2.7 feedback.  Perhaps CT ratio is too high for a relatively low primary current coil.

Quote
Final note on testing: I am using a multi turn primary with 8 turns. I have several caps soldered in place to be able to easily add and remove them. I use two 10nF caps as well as several small 6.8nF for smaller increments. I measured the primary Fres which came out to 310kHz but when the coil was running , bridge output and feedback both showed it running over 500kHz... what could cause this? The secondary Fres without a topload was 530kHz, with a topload and 20in wire, it dropped to 360kHz. So the primary seems to be running far off from resonance.
Once you measure upper pole frequency, see if that is close.  For initial experiments I'd include top load but no arc-simulation wire.  If operating frequency doesn't match upper pole, then perhaps self-oscillation component values are such that it oscillates at too high a frequency.  Might help to post your schematic as it is now including any self-oscillation modifications.

Quote
Sometimes I get what looks like a good primary tap & MMC but then OCD trips at or near120v. So I make a slight adjustment but then OCD trips at a much lower voltage. If it doesn't trip then the arcs are loud, snappy and branched.  >:( 
Scope current during these conditions to see what actual values are, along with frequency and shape.  Scoping across 51 ohm CT burden resistor is a good option (doesn't require another CT just for scoping).  If SV1 is set for phase lead, scope across just 51 ohms, not including phase-lead inductor.

Quote
How might I assume a safe primary current for my IGBTs? I know Loneoceans has a section on how OCD CT voltage correlates to current and how to adjust that voltage via R10 but I am wondering how you can assume this part can run a 250A or 500A?
Ramped coils have long on-times (quarter or half line cycle).  Rated peak currents are generally for 1ms, 225A I think for your part.  I wouldn't go above 250A for a ramped coil.
David Knierim

Offline ZakW

  • High Voltage Technician
  • ***
  • Posts: 179
  • Karma: +6/-0
  • YouTube @QZW_Labs
    • View Profile
Re: RDRSSTC - Project Build
« Reply #30 on: January 14, 2024, 02:27:58 AM »
Quote
Yes for the two pole frequencies.  Probably easiest to measure the assembled system through the primary.  Have secondary in place, bottom grounded and top to top load (and arc simulation wire if you want loaded frequencies).  Then measure frequencies the same way you measured the single isolated primary frequency.
I'll give that a shot.

Quote
SV1 can be installed in either position (with or without phase lead), just not left open.  UD2.7 CT (SV1) voltages are intended to be high, often peak at 50 to 100V.  Without SV1 installed, voltage can go even higher, so fry resistors.  However, in your case, perhaps CT secondary current is too low for reliable US2.7 feedback.  Perhaps CT ratio is too high for a relatively low primary current coil.
Being completely unfamiliar with the UD, I only installed a 2 pin header instead of a 3 pin. I see now why it is a 3 pin header. My only option is to run SV1 closed unless I remove the inductor and short the connection.

I still need to check the 1K resistor (R6) to make sure it is not fried.

For the inductor I took apart a misc part that I had on hand and added a couple layers and measured with LC meter until I was around "9 - 15uH; works well with TO247 IGBTs" - loneoceans. I can move the slug up or down to vary the inductance. I think that should be fine.



Quote
Scope current during these conditions to see what actual values are, along with frequency and shape.  Scoping across 51 ohm CT burden resistor is a good option (doesn't require another CT just for scoping).  If SV1 is set for phase lead, scope across just 51 ohms, not including phase-lead inductor.
ground lead would be connected to TP1, but are you saying to then scope at TP2 or 3?



Updated schematic using logic symbols instead of IC's. Added notes about things I need to update but this schematic is accurate for the modifications I have made so far.



Quote
However, in your case, perhaps CT secondary current is too low for reliable US2.7 feedback.  Perhaps CT ratio is too high for a relatively low primary current coil.
Quote
Ramped coils have long on-times (quarter or half line cycle).  Rated peak currents are generally for 1ms, 225A I think for your part.  I wouldn't go above 250A for a ramped coil.
My CT is 33:1:25, so 825:1

I'll have to check loneoceans notes on calculating the output voltage given my turns ratio in order to figure out how to set the OCD to the correct value. So far nothing as died so I am grateful for that. Wish my last SSTC had OCD, would have save so much $$$!

Thanks for the all the information!

Offline davekni

  • Executive Board Member
  • *******
  • Posts: 2680
  • Karma: +127/-1
  • Physicist, engineer (electronic), and hobbiest
    • View Profile
Re: RDRSSTC - Project Build
« Reply #31 on: January 14, 2024, 03:38:08 AM »
Quote
ground lead would be connected to TP1, but are you saying to then scope at TP2 or 3?
Yes, ground to TP1 and probe to TP2.  That is scoping directly across 51 ohm resistor.  Represents current that way.  (TP3 includes phase lead, so would be leading actual current phase and a bit higher amplitude too.)

Quote
Updated schematic using logic symbols instead of IC's. Added notes about things I need to update but this schematic is accurate for the modifications I have made so far.
Thank you.  Makes discussion much clearer.  BTW, self oscillation may work better if R6 is increased from 1k to ~5k as mentioned near the end of this post:
    https://highvoltageforum.net/index.php?topic=1914.msg14854#msg14854
Above post recommends changing R2, the label from common UD2.7 schematics.  This is R6 for your schematic.  Increasing R6 value should help make self-oscillation frequency more stable and easier to adjust.

Without self-oscillation, using 4148 diodes increases CT feedback voltage necessary to start oscillation, relative to UD2.7 schematic that uses schottky diodes.  (Some UD2.7 versions use 1N4148 instead.)  However, 1N4148 or equivalent is good for a self-oscillating version as you now have.

Quote
My CT is 33:1:25, so 825:1
Thus for feedback CT input, +-250A primary becomes 250/825=0.303A, which is +-15.45V across 51 ohms.  Should be fine.

Quote
I'll have to check loneoceans notes on calculating the output voltage given my turns ratio in order to figure out how to set the OCD to the correct value.
Hope I'm not encouraging you to become too lazy by calculating for you.  Fairly simple.  0.303V becomes 3.03V across 10 ohm OCD burden resistor.  Because shutdown takes a cycle (where current can continue to increase slightly), set trip point slightly under 3.03V.

Quote
For the inductor I took apart a misc part that I had on hand and added a couple layers and measured with LC meter until I was around "9 - 15uH; works well with TO247 IGBTs" - loneoceans. I can move the slug up or down to vary the inductance. I think that should be fine.
For a crude approximation, 9uH/51ohms=176ns.  15uH/51ohms=294ns.  This approximation only works when frequency is low enough where 294ns is a small fraction of 90 degrees (of 1/4 cycle).  In your high frequency use, time lead will be less than this simple calculation.  So you may need more inductance depending on both IGBT speed and delay through driver.  Driver delay can be reduced a little by using AC08 instead of HC08.  But AC08 requires good ground plane and supply bypassing due to fast switching.  Use only if ECB layout is good and AC08 is not in a socket.

Quote
Thanks for the all the information!
You're welcome.  Glad it's been useful.
David Knierim

Offline ZakW

  • High Voltage Technician
  • ***
  • Posts: 179
  • Karma: +6/-0
  • YouTube @QZW_Labs
    • View Profile
Re: RDRSSTC - Project Build
« Reply #32 on: January 14, 2024, 04:21:43 AM »
Quote
Thank you.  Makes discussion much clearer.  BTW, self oscillation may work better if R6 is increased from 1k to ~5k as mentioned near the end of this post:
I missed that recommendation. I will give that a try.

Quote
Without self-oscillation, using 4148 diodes increases CT feedback voltage necessary to start oscillation
Not quite sure I follow. Regardless of the self-oscillation mod are you suggesting to swap out D1 & D2 with 4148 type diodes?



Quote
Hope I'm not encouraging you to become too lazy by calculating for you.  Fairly simple.  0.303V becomes 3.03V across 10 ohm OCD burden resistor.  Because shutdown takes a cycle (where current can continue to increase slightly), set trip point slightly under 3.03V.
Not at all. On the contrary, I was trying not to be a burden by asking you for step by step instructions but I appreciate you doing it. I am adding as much as I can to my notes so I can reference these calculations in the future. Growing up I always copied schematics and never invested time into learning theory. So now I am trying to increase my understanding via projects but it can be tough.

Quote
For a crude approximation, 9uH/51ohms=176ns.  15uH/51ohms=294ns.  This approximation only works when frequency is low enough where 294ns is a small fraction of 90 degrees (of 1/4 cycle).  In your high frequency use, time lead will be less than this simple calculation.  So you may need more inductance depending on both IGBT speed and delay through driver.  Driver delay can be reduced a little by using AC08 instead of HC08.  But AC08 requires good ground plane and supply bypassing due to fast switching.  Use only if ECB layout is good and AC08 is not in a socket.
That makes sense, I guess I can make that determination after I scope across the CT resistor. I am comparing the CT feedback to the primary output, right? A lot of DRSSTC scope shots I see dont always label the traces.







« Last Edit: January 14, 2024, 04:38:47 AM by ZakW »

Offline davekni

  • Executive Board Member
  • *******
  • Posts: 2680
  • Karma: +127/-1
  • Physicist, engineer (electronic), and hobbiest
    • View Profile
Re: RDRSSTC - Project Build
« Reply #33 on: January 14, 2024, 04:52:35 AM »
Quote
Not quite sure I follow. If I wasn't using the self-oscillation mod are you suggesting to swap out D1 & D2 with 4148 type diodes or add diodes like the OCD CT input?
The schematic you show in above post shows MBR0530, a schottky diode as used in most UD2.7 schematics.  This is best for standard UD2.7 without self-oscillating mods.  This post explains normal (not self-oscillating) startup a bit, though for an SSTC circuit with HC14 feedback:
    https://highvoltageforum.net/index.php?topic=840.msg5667#msg5667
UD2.7 input startup is similar.  CT feedback voltage required from first half-cycle is the forward voltage drop of D1 with ~14uA of current flowing through it (quiescent current through 100k R27).  Schottky diodes have much lower Vf, especially at low current, making startup easier.  (D1 is from above post, which is D6 in your schematic.  R27 is R3 in your schematic.)
However, for self-oscillation, schottky diodes clamp the self-oscillation feedback voltage to a low value, reducing frequency stability.  1N4148 diodes allow more voltage there for cleaner self-oscillation.  Because voltage is already oscillating at close to operating frequency, little additional CT feedback voltage is needed to lock to coil frequency.  The higher Vf doesn't increase required startup CT feedback voltage in self-oscillating configuration.

Quote
Not at all. On the contrary, I was trying not to be a burden by asking you for step by step instructions but I appreciate you doing it. I am adding as much as I can to my notes so I can reference these calculations in the future. Growing up I always copied schematics and never invested time into learning theory. So now I am trying to increase my understanding via projects but it can be tough.
An excellent way to increase understanding is with analog simulation.  Many free options available.  My favorite is LTSpice.  Analyzing self oscillation of just the comparitor circuit would be a good place to start.  Doesn't require simulating entire coil.

Quote
I am comparing the CT feedback to the primary output, right?
Yes,  CT feedback current across 51 ohm resistor only (TP2 to TP1 from previous post).  Or some people use a third CT with separate burden resistor for scoping.

Quote
A lot of DRSSTC scope shots I see dont always label the traces.
Yes, that is a common problem that I sometimes complain about.  Hard to respond appropriately to unlabeled scope traces.
« Last Edit: January 14, 2024, 04:54:09 AM by davekni »
David Knierim

Offline ZakW

  • High Voltage Technician
  • ***
  • Posts: 179
  • Karma: +6/-0
  • YouTube @QZW_Labs
    • View Profile
Re: RDRSSTC - Project Build
« Reply #34 on: January 14, 2024, 05:04:58 AM »
Quote
The schematic you show in above post shows MBR0530, a schottky diode as used in most UD2.7 schematics.  This is best for standard UD2.7 without self-oscillating mods.  This post explains normal (not self-oscillating) startup a bit, though for an SSTC circuit with HC14 feedback:
    https://highvoltageforum.net/index.php?topic=840.msg5667#msg5667
UD2.7 input startup is similar.  CT feedback voltage required from first half-cycle is the forward voltage drop of D1 with ~14uA of current flowing through it (quiescent current through 100k R27).  Schottky diodes have much lower Vf, especially at low current, making startup easier.  (D1 is from above post, which is D6 in your schematic.  R27 is R3 in your schematic.)
However, for self-oscillation, schottky diodes clamp the self-oscillation feedback voltage to a low value, reducing frequency stability.  1N4148 diodes allow more voltage there for cleaner self-oscillation.  Because voltage is already oscillating at close to operating frequency, little additional CT feedback voltage is needed to lock to coil frequency.  The higher Vf doesn't increase required startup CT feedback voltage in self-oscillating configuration.
Thanks for that, I will take a look at that post. I copied the 2.1b schematic which uses MCL4148 diodes instead of the MBR0530. I have some regular 1N4148W diodes I can try in their place.

Quote
An excellent way to increase understanding is with analog simulation.  Many free options available.  My favorite is LTSpice.  Analyzing self oscillation of just the comparitor circuit would be a good place to start.  Doesn't require simulating entire coil.
I have been meaning to get more into simulation. It is on my list to start practicing.


Offline davekni

  • Executive Board Member
  • *******
  • Posts: 2680
  • Karma: +127/-1
  • Physicist, engineer (electronic), and hobbiest
    • View Profile
Re: RDRSSTC - Project Build
« Reply #35 on: January 14, 2024, 05:15:53 AM »
Quote
Thanks for that, I will take a look at that post. I copied the 2.1b schematic which uses MCL4148 diodes instead of the MBR0530. I have some regular 1N4148W diodes I can try in their place.
I expect any diode with "4148" in part number has similar characteristics to the original 1N4148.  No reason to change parts.
David Knierim

Offline ZakW

  • High Voltage Technician
  • ***
  • Posts: 179
  • Karma: +6/-0
  • YouTube @QZW_Labs
    • View Profile
Re: RDRSSTC - Project Build
« Reply #36 on: January 14, 2024, 05:22:38 AM »
I decreased R6 (normally a 1K (R2 in 2,1b)) to 560ohms and now I am getting a much better closer to operating frequency output range. Before I swapped out the 1K resistor with a 5K and the TL3116 was oscillating at most several mHz anything lower than 1mHz was not stable. I am using a 50k POT for adjustment.

I will take the other measurements and share my findings, probably tomorrow.


Offline davekni

  • Executive Board Member
  • *******
  • Posts: 2680
  • Karma: +127/-1
  • Physicist, engineer (electronic), and hobbiest
    • View Profile
Re: RDRSSTC - Project Build
« Reply #37 on: January 14, 2024, 05:31:22 AM »
Quote
I decreased R6 (normally a 1K (R2 in 2,1b)) to 560ohms and now I am getting a much better closer to operating frequency output range. Before I swapped out the 1K resistor with a 5K and the TL3116 was oscillating at most several mHz anything lower than 1mHz was not stable. I am using a 50k POT for adjustment.
Just looked back at your updated schematic from a few posts ago.  C15 will need to be larger than 220pF, ~1nF, to go along with 5K for R6.  I'd recommend changing C15 rather than going so low for R6 value.
David Knierim

Offline ZakW

  • High Voltage Technician
  • ***
  • Posts: 179
  • Karma: +6/-0
  • YouTube @QZW_Labs
    • View Profile
Re: RDRSSTC - Project Build
« Reply #38 on: January 14, 2024, 06:15:53 AM »
Here are scope captures showing phase lag/lead.

Purple = probe across 51 ohm resistor
Blue = bridge output
Yellow = TL3116 output (I don't think it applies, just had the input on during captures)

This is with the ferrite slug fully seated





Switching looks good to me, not a lot of spikes.



This is with the slug removed





Switching looks worse, is that too much lead?

Edit: Looking at the first picture I am trying to calculate the primary current.

Isecondary=Vburden/Rburden

4.56V/51ohms = 0.089A

Iprimary = Isecondary * Turns ratio

0.089A * 825 turns = 73.43A flowing through the primary?
« Last Edit: January 14, 2024, 06:30:05 AM by ZakW »

Offline davekni

  • Executive Board Member
  • *******
  • Posts: 2680
  • Karma: +127/-1
  • Physicist, engineer (electronic), and hobbiest
    • View Profile
Re: RDRSSTC - Project Build
« Reply #39 on: January 14, 2024, 07:53:58 PM »
Quote
This is with the ferrite slug fully seated
Quote
Switching looks good to me, not a lot of spikes.
Looks reasonable, but would be better with slightly more phase lead.  You'll need a bit higher inductance to get enough.

Quote
Switching looks worse, is that too much lead?
No, this is far too little phase lead.  Slug removed is minimum inductance so minimum phase lead.

Quote
0.089A * 825 turns = 73.43A flowing through the primary?
Yes.

BTW, for a bit of detail, look at the little bumps in bridge out just prior to switching in your first two slug-in scope captures.  In the second of those first two (at 50ns/div), the bump lasts roughly from division 3 to 4, with the main switching starting at division 4.6.  The beginning of that bump at division 3 is when one set of IGBTs turns off.  The end of the bump at division 4 is when current reverses, pulling bridge output back to it's previous value.  Then opposite set of IGBTs turns on starting at division 4.6.  (Current sense trace appears to be ~70ns delayed from reality.  Not sure exactly why, but seems somewhat common.  Perhaps due to parasitics of CT.)  With ideal phase lead, that bump becomes the real output transition and opposite IGBTs turn on just as current is passing through zero, around 100ns more phase lead than you have now.
David Knierim

Offline ZakW

  • High Voltage Technician
  • ***
  • Posts: 179
  • Karma: +6/-0
  • YouTube @QZW_Labs
    • View Profile
Re: RDRSSTC - Project Build
« Reply #40 on: January 14, 2024, 09:38:24 PM »
Quote
Looks reasonable, but would be better with slightly more phase lead.  You'll need a bit higher inductance to get enough.
More phase lead. Inductor values: With slug 34.1uH, without 7.1uH.

Currently, I have it about halfway seated. If the goal was to reduce that dip as much as possible I think where I have it set now is it.







Quote
No, this is far too little phase lead.  Slug removed is minimum inductance so minimum phase lead.
Oops, I was looking at that backwards.

Quote
BTW, for a bit of detail, look at the little bumps in bridge out just prior to switching in your first two slug-in scope captures.  In the second of those first two (at 50ns/div), the bump lasts roughly from division 3 to 4, with the main switching starting at division 4.6.  The beginning of that bump at division 3 is when one set of IGBTs turns off.  The end of the bump at division 4 is when current reverses, pulling bridge output back to it's previous value.  Then opposite set of IGBTs turns on starting at division 4.6.  (Current sense trace appears to be ~70ns delayed from reality.  Not sure exactly why, but seems somewhat common.  Perhaps due to parasitics of CT.)  With ideal phase lead, that bump becomes the real output transition and opposite IGBTs turn on just as current is passing through zero, around 100ns more phase lead than you have now.
I appreciate the breakdown, thanks!



The arcs seem to all be splitting, usually into two from the breakout. I have yet to get a single straight arc. In an effort to get straighter arcs I am going to try and increase primary impedance by winding a new primary. Currently I am using high MMC value with few turns. I am going to try and reverse that to see if I can slow arc growth down a bit to reduce branching.

Offline davekni

  • Executive Board Member
  • *******
  • Posts: 2680
  • Karma: +127/-1
  • Physicist, engineer (electronic), and hobbiest
    • View Profile
Re: RDRSSTC - Project Build
« Reply #41 on: January 15, 2024, 02:50:56 AM »
Quote
Currently, I have it about halfway seated. If the goal was to reduce that dip as much as possible I think where I have it set now is it.
Looks good, though I'd consider setting it for slightly more phase lead still (slug farther in).

Quote
The arcs seem to all be splitting, usually into two from the breakout. I have yet to get a single straight arc. In an effort to get straighter arcs I am going to try and increase primary impedance by winding a new primary. Currently I am using high MMC value with few turns. I am going to try and reverse that to see if I can slow arc growth down a bit to reduce branching.
Sounds like a good plan.  I'm certainly no expert on making single straight arcs, but slower ramp rate fits my limited experience.
Edit:  Another change to try is increasing breakout point length.  Found with my QCW coil that if breakout was too short more voltage was required to start arc (as expected).  That higher voltage caused immediate branching as arc grew rapidly initially.
« Last Edit: January 15, 2024, 03:33:08 AM by davekni »
David Knierim

Offline yourboi

  • High Voltage Enthusiast
  • *
  • Posts: 26
  • Karma: +0/-0
    • View Profile
Re: RDRSSTC - Project Build
« Reply #42 on: January 18, 2024, 10:40:47 PM »
Hi I'm just lurking around this thread. Do you have a copy of the 3d print file for the igbt clips? They look pretty solid. Thank you for your time.

Offline ZakW

  • High Voltage Technician
  • ***
  • Posts: 179
  • Karma: +6/-0
  • YouTube @QZW_Labs
    • View Profile
Re: RDRSSTC - Project Build
« Reply #43 on: January 19, 2024, 03:31:23 AM »
Quote
Hi I'm just lurking around this thread. Do you have a copy of the 3d print file for the igbt clips? They look pretty solid. Thank you for your time.
Sure happy too!

I just tired uploading the .OBJ file and .stil but I am not allowed to on this site. I will try saving them to a google drive and linking them.

Edit: Sent you a pm
« Last Edit: January 19, 2024, 04:06:50 AM by ZakW »

Offline ZakW

  • High Voltage Technician
  • ***
  • Posts: 179
  • Karma: +6/-0
  • YouTube @QZW_Labs
    • View Profile
Re: RDRSSTC - Project Build
« Reply #44 on: January 19, 2024, 10:06:31 PM »
Bit of an update, in my quest for straighter arcs that split and branch less I am starting to run into an issue. I have tested MANY configurations and so far haven't found a solution yet but I am now noticing some odd behavior from the driver.

I am not sure if it is due to the self-oscillation mod but the driver wont lock onto the primary feedback and oscillate at that frequency. Regardless of what I have the self-oscillation signal set at at, above or below the primary Fres it doesn't seem to kick it out of that mode. It typically oscillates around 250kHz. This occurs the closer I get to matching the primary Fres with the secondary. If it was the oscillation mod I would expect to see the feedback frequency change as I adjust the POT but it doesn't.

Here is an example of what is happening. The coil is running at around 270kHz in the beginning and then switches to running at 397kHz, which happens to be what I measured the secondary Fres at with the current topload and primary in place (open circuit). If I change the primary Fres by added or reducing capacitance I can get the coil to run on feedback again but of course the output suffers. I know that ideally the primary is detuned slightly to compensate for arc loading but I just wanted to share this behavior.

Blue= bridge output
purple= primary feedback across CT resistor

Phase lead isn't ideal either, I was just doing some quick tests.






This shows where the transition occurs.


Any ideas what could cause this? Sometimes the whole on-time of the coil will be with it running around 250-270kHz, primary current (purple) just stays flat around 2 volts depending. When it is operating on primary feedback the current usually spikes towards peak voltage.

Update: So I was messing with it some more and noticed when I turned the self oscillation frequency too high the arcs were curving downward and striking the MMC. I am running it without a topload since arcs seem to be a bit more straight. The low side resulted in louder arcs and more branching.

I was curious to see if the higher self oscitation freq was causing the arcs to curve due to being above the sweet spot (350-450ishKHz).

Purple = CT feedback
Blue = bridge output
yellow = tl3116 pin 7 output.

Overall ramp profile

Zooming in on the beginning we can see it is running at off of the self oscillation frequency +600kHz before it switches to the actual primary frequency. 




I can get straighter arcs by setting the mod closer to the primary Fres but they are still splitting. The only time I managed to get short straight arcs was when I used around 20turns on a primary and low capacitance. Output was poor but they were straight. Any other ideas for how I might get them to stop splitting initially?

« Last Edit: January 20, 2024, 02:24:47 AM by ZakW »

Offline davekni

  • Executive Board Member
  • *******
  • Posts: 2680
  • Karma: +127/-1
  • Physicist, engineer (electronic), and hobbiest
    • View Profile
Re: RDRSSTC - Project Build
« Reply #45 on: January 20, 2024, 06:02:14 AM »
Quote
This shows where the transition occurs.
H-bridge output voltage is varying, probably due to a parasitic resonance of local bridge snubber cap(s) and bulk cap(s).  Such resonances are common and usually not a problem.  However, occasionally they are problematic, such as when at 2x coil operating frequency.  Not sure if this is contributing to any of your issues or not.  You can try adding snubber capacitance or reducing interconnect inductance to bulk caps to see if either helps.
Edit:  Forgot, no bulk caps on an ramped coil.  Perhaps some other resonance between snubber caps or ...

Quote
Here is an example of what is happening. The coil is running at around 270kHz in the beginning and then switches to running at 397kHz, which happens to be what I measured the secondary Fres at with the current topload and primary in place (open circuit).
Looks like switching from lower pole frequency to upper pole frequency.  Much more common problem is reverse of that.  Perhaps upper pole frequency with a bit of arc loading happens to match your measured secondary frequency.

What self-resonant values are you using now?  Did you make any changes per my reply #37?

Feedback amplitude is on the low side of typical.  1000:1 CT may be too high a ratio for your relatively-low-current coil.  I'd consider reducing CT ratio for more reliable feedback.  However, that may make no difference.  Even your low feedback amplitude appears to be sufficient.

Quote
The only time I managed to get short straight arcs was when I used around 20turns on a primary and low capacitance. Output was poor but they were straight. Any other ideas for how I might get them to stop splitting initially?
Yes, slow ramps make for straight arcs.  The hard part is getting ramp fast enough for long arcs while starting smoothly enough to avoid branching.  Being limited to ramp shape of line quarter-cycle is an extra constraint compared to QCW.  However, I see successful line ramped coils here.  Perhaps someone with a good result can offer ideas.
« Last Edit: January 20, 2024, 06:06:23 PM by davekni »
David Knierim

Offline ZakW

  • High Voltage Technician
  • ***
  • Posts: 179
  • Karma: +6/-0
  • YouTube @QZW_Labs
    • View Profile
Re: RDRSSTC - Project Build
« Reply #46 on: January 21, 2024, 10:18:40 PM »
Quote
H-bridge output voltage is varying, probably due to a parasitic resonance of local bridge snubber cap(s) and bulk cap(s).  Such resonances are common and usually not a problem.  However, occasionally they are problematic, such as when at 2x coil operating frequency.  Not sure if this is contributing to any of your issues or not.  You can try adding snubber capacitance or reducing interconnect inductance to bulk caps to see if either helps.
Edit:  Forgot, no bulk caps on an ramped coil.  Perhaps some other resonance between snubber caps or ...
I will try adding some snubber capacitors. My leads from the full bridge PCB to the MMC and coil primary are longer than I want but make testing easier, I know that is not ideal.

Using the formula from Mads site https://kaizerpowerelectronics.dk/tesla-coils/drsstc-design-guide/snubber-capacitor/:

Assumptions:
Ls = 200nH
Ipeak = 200A
Vtransient = 500V
Vbus = 200V

= 88.9nF, just wanted to get a rough estimate.

Quote
Looks like switching from lower pole frequency to upper pole frequency.  Much more common problem is reverse of that.  Perhaps upper pole frequency with a bit of arc loading happens to match your measured secondary frequency.

What self-resonant values are you using now?
5 turns on my primary and 20-30nF for my resonant cap. The issue doesn't seem to show up when I am above the resonant frequency of the secondary. I check my primary output and CT feedback frequency if it is to high I add a small amount (2.2nF) and remeasure, I see the primary frequency drop accordingly but as soon as I get close to resonance (coil with topload = 462kHz) the primary switches to a much lower frequency (around 350Khz), much lower than what adding a single 2.2nF cap would cause.

Quote
  Did you make any changes per my reply #37?
I am missing where the post number is, can you link it for me?

Offline davekni

  • Executive Board Member
  • *******
  • Posts: 2680
  • Karma: +127/-1
  • Physicist, engineer (electronic), and hobbiest
    • View Profile
Re: RDRSSTC - Project Build
« Reply #47 on: January 21, 2024, 10:30:44 PM »
Quote
5 turns on my primary and 20-30nF for my resonant cap. The issue doesn't seem to show up when I am above the resonant frequency of the secondary. I check my primary output and CT feedback frequency if it is to high I add a small amount (2.2nF) and remeasure, I see the primary frequency drop accordingly but as soon as I get close to resonance (coil with topload = 462kHz) the primary switches to a much lower frequency (around 350Khz), much lower than what adding a single 2.2nF cap would cause.
This is normal behavior for standard drivers without self-oscillation.  If primary frequency is slightly above secondary, oscillation is at upper pole.  If primary is slightly below secondary, jumps to lower pole.  Self-oscillation can help force upper pole operation, but only if primary frequency isn't too far below secondary.

Quote
I am missing where the post number is, can you link it for me?
Look at the top of each post to any thread.  There's a line such as this one from your last post:
     « Reply #46 on: Today at 10:18:40 PM »
I'm referring to reply 37 of this thread, 9 posts before your above one.  It's in page 2 of this thread.  In case that isn't clear enough:
    https://highvoltageforum.net/index.php?topic=2651.msg20288#msg20288
David Knierim

Offline ZakW

  • High Voltage Technician
  • ***
  • Posts: 179
  • Karma: +6/-0
  • YouTube @QZW_Labs
    • View Profile
Re: RDRSSTC - Project Build
« Reply #48 on: January 22, 2024, 01:00:02 AM »
Quote
Look at the top of each post to any thread.  There's a line such as this one from your last post:
     « Reply #46 on: Today at 10:18:40 PM »
I'm referring to reply 37 of this thread, 9 posts before your above one.  It's in page 2 of this thread.  In case that isn't clear enough:
    https://highvoltageforum.net/index.php?topic=2651.msg20288#msg20288
Got it, I see the post number now. Missed that earlier.

Quote
Just looked back at your updated schematic from a few posts ago.  C15 will need to be larger than 220pF, ~1nF, to go along with 5K for R6.  I'd recommend changing C15 rather than going so low for R6 value.
I did update the values and it helped to reduce the upper limit frequency. Making adjustments easier.

Quote
This is normal behavior for standard drivers without self-oscillation.
I am confused because I am using self oscillation.

Like you mentioned I probably want to aim for upper pole operation. For my current Secondary I measured the resonant frequency with the primary in place but open circuit. It was around 462kHz with a topload, no wire for streamer loading. So upper pole is going to be a bit above that? That is what I want to tune my primary for, slightly above 462kHz? If that is the case then I also want to run the oscillation mod at or around that frequency as well, right?

Offline davekni

  • Executive Board Member
  • *******
  • Posts: 2680
  • Karma: +127/-1
  • Physicist, engineer (electronic), and hobbiest
    • View Profile
Re: RDRSSTC - Project Build
« Reply #49 on: January 22, 2024, 05:30:27 AM »
Quote
I am confused because I am using self oscillation.
Just mentioning that your experience was matching normal w/o self oscillation.  Appears for some reason self oscillation isn't helping force upper pole frequency.

Quote
So upper pole is going to be a bit above that?
Yes.  How far above depends on coupling (and on primary frequency).  High coupling (generally good for QCW and ramped coils) makes upper pole frequency higher and lower pole frequency lower.

Quote
That is what I want to tune my primary for, slightly above 462kHz?
If self oscillation doesn't work to allow lower primary frequency, then yes.

Quote
If that is the case then I also want to run the oscillation mod at or around that frequency as well, right?
If using self oscillation only to start oscillation and not to force upper pole operation, then yes.

Self oscillation can cause upper pole operation even with primary frequency lower than secondary frequency.  That's what my QCW coil does.  However, I think that works best when primary-to-secondary coupling is high.  My QCW coupling is higher than most at 0.7.  I think one or two other forum members have had success with self oscillation forcing upper pole with coupling around 0.4 or 0.45.  Not sure if anyone has tried with lower coupling than that.
David Knierim

Offline ZakW

  • High Voltage Technician
  • ***
  • Posts: 179
  • Karma: +6/-0
  • YouTube @QZW_Labs
    • View Profile
Re: RDRSSTC - Project Build
« Reply #50 on: February 14, 2024, 01:58:17 AM »
Started tinkering again after a short break. Seems like I was able to fix a couple issues, but splitting arcs is my main problem now.

Significantly shortening primary connections and increasing coupling seems to have fixed the pole switching issue as well as the primary not changing its frequency when the tank cap is adjusted. Wrapping the primary directly to the secondary outer former I was able to get a coupling of 0.57k, per JavaTC.

Arc splitting:
  • I have tried everything I can think of to get the arcs to be straighter. So far, the best I can get is without a topload, the arcs are long but they split at the breakout point to form a V but it is very consistent. Both arcs are about ~21in long. With a topload I get several main arcs that then split along their length as well.
  • I have tried increasing primary turns to around 13 all the way down to 2. Higher turns at lower voltage produces much shorter but straighter arcs, at higher input voltage they begin to split all the same. Lower turns significantly increase arc current but can lead to more splitting. 5-6T seems to be the sweet spot.
  • I tested short stubby coils as well as long tall coils, geometry doesn't seem to make a major difference. Best results so far with the shorter coil.
  • Running the coil at higher Fres doesn't seem to reduce splitting either
Looking back on my RSSTC build, I could adjust the primary height to fix arc splitting. Lower primary made for shorter straighter arcs, while raising it caused the arcs to get longer it also made them split at a certain point. Adjusting the primary height with this build doesn't seem to have the same effect if any really.

Could a full bridge DRSSTC simply be supplying too much power to the coil for such a short ramp time with arc splitting being largely unavoidable?

Any ideas or advice would be appreciated.

-Zak

Offline davekni

  • Executive Board Member
  • *******
  • Posts: 2680
  • Karma: +127/-1
  • Physicist, engineer (electronic), and hobbiest
    • View Profile
Re: RDRSSTC - Project Build
« Reply #51 on: February 14, 2024, 05:32:30 AM »
Quote
Could a full bridge DRSSTC simply be supplying too much power to the coil for such a short ramp time with arc splitting being largely unavoidable?
Certainly one possibility.  Ramped coil doesn't allow changing ramp rate as a QCW coil does.  Another possibility is that feedback doesn't take over from self-oscillation at low enough voltage.  Scope primary current during ramp.  If it jumps up suddenly too far into the ramp (at too high line voltage), that sudden start may be causing branching.  Sudden jump in current may happen when feedback takes over, making frequency match (presumably upper) pole frequency.  If that is the issue, adjust self-oscillation frequency to more closely match upper pole frequency.  (Match frequency just before current jump to frequency after.)
« Last Edit: February 14, 2024, 06:07:17 AM by davekni »
David Knierim

Offline ZakW

  • High Voltage Technician
  • ***
  • Posts: 179
  • Karma: +6/-0
  • YouTube @QZW_Labs
    • View Profile
Re: RDRSSTC - Project Build
« Reply #52 on: February 14, 2024, 06:25:45 PM »
Quote
Another possibility is that feedback doesn't take over from self-oscillation at low enough voltage.  Scope primary current during ramp.  If it jumps up suddenly too far into the ramp (at too high line voltage), that sudden start may be causing branching.  Sudden jump in current may happen when feedback takes over, making frequency match (presumably upper) pole frequency.  If that is the issue, adjust self-oscillation frequency to more closely match upper pole frequency.  (Match frequency just before current jump to frequency after.)
*I will edit this post and attach the scope capture later.*

I forgot to mention a couple other changes I made. I reduced gate resistance for each IGBT from 15ohms to 10ohms and shortened the GDT output connections.

To your point when I was testing the other day, I probed the self oscillation output, CT output and primary. With the changes I made the self oscillation appeared to switch as soon as the ramp starts. I did not zoom in super close but the current ramped up smoothly as expected (like what I would see with my SSTC). I will post the capture for this later.

The oscillation mod is acting differently too (in a good way), it is more sensitive and usually has to be set quite high. Before it would work below or above resonance. I think Rafft had a similar experience with his QCW coil. It typically runs somewhere around 650kHz, going far above that causes no oscillation and running at a lower frequency causes primary to secondary arcing. Again, a similar issue I had with my RSSTC.



EDIT: Scope captures.

Yellow=Self oscillation output
Purple=primary current via CT
Blue=Primary output

Self oscillation is running around 781kHz before the coil turns on. Looks like that drops to 625kHz on startup and then all the way down to 490kHz at the halfway point.









« Last Edit: February 15, 2024, 05:57:24 AM by ZakW »

Offline davekni

  • Executive Board Member
  • *******
  • Posts: 2680
  • Karma: +127/-1
  • Physicist, engineer (electronic), and hobbiest
    • View Profile
Re: RDRSSTC - Project Build
« Reply #53 on: February 15, 2024, 07:11:20 PM »
Quote
EDIT: Scope captures.

Yellow=Self oscillation output
Purple=primary current via CT
Blue=Primary output

Self oscillation is running around 781kHz before the coil turns on. Looks like that drops to 625kHz on startup and then all the way down to 490kHz at the halfway point.
Scope captures all look good.  Thank you for posting.
David Knierim

Offline ZakW

  • High Voltage Technician
  • ***
  • Posts: 179
  • Karma: +6/-0
  • YouTube @QZW_Labs
    • View Profile
Re: RDRSSTC - Project Build
« Reply #54 on: February 16, 2024, 03:50:58 AM »
Had my first bridge failure. Not bad considered I killed around ~15 or more IGBTs & MOSFETs with my RSSTC.

OCD did not seem to trigger when it failed. I might have it adjusted too high.

I did have moderate success with some initial testing to reduce arc branching. I added a small wire wound inductor on the primary output in an effort to limit the initial current to the primary. I was only able to mess with the coil and look at the scope for a bit before it failed. But it managed to reduce branching quite a bit! Primary current was much lower for ~1.5ms or so before ramping up as usual, I think this is what helped to reduce branching. The coil failed after reducing the tank cap. I will have to take a look at it more this weekend and see what I can find out and do some more testing.

Offline davekni

  • Executive Board Member
  • *******
  • Posts: 2680
  • Karma: +127/-1
  • Physicist, engineer (electronic), and hobbiest
    • View Profile
Re: RDRSSTC - Project Build
« Reply #55 on: February 17, 2024, 08:56:42 PM »
Quote
Primary current was much lower for ~1.5ms or so before ramping up as usual, I think this is what helped to reduce branching.
Agree, that sounds likely.  Slower start helps reduce branching.  However, whatever is causing that change 1.5ms into ramp might be a cause of failure.  Only guess that comes to mind is that feedback isn't taking over from self-oscillation for initial 1.5ms under conditions of this test.
David Knierim

Offline ZakW

  • High Voltage Technician
  • ***
  • Posts: 179
  • Karma: +6/-0
  • YouTube @QZW_Labs
    • View Profile
Re: RDRSSTC - Project Build
« Reply #56 on: February 17, 2024, 10:20:39 PM »
Quote
However, whatever is causing that change 1.5ms into ramp might be a cause of failure.  Only guess that comes to mind is that feedback isn't taking over from self-oscillation for initial 1.5ms under conditions of this test.
That is what I was thinking too but I did not get the chance to do enough testing. Since I haven't had a failure until recently these are the original IGBTs and I think I have stressed them A LOT. I noticed some uneven heating in two of the IGBTs before they failed so I think they were already compromised.

I will do some more testing and post my results.

High Voltage Forum

Re: RDRSSTC - Project Build
« Reply #56 on: February 17, 2024, 10:20:39 PM »

 


* Recent Topics and Posts

post Re: LabCoatz Staccato QCW No straight sparks
[Dual Resonant Solid State Tesla coils (DRSSTC)]
alan sailer
Today at 12:53:22 AM
post Re: LabCoatz Staccato QCW No straight sparks
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ZakW
February 21, 2024, 11:37:47 PM
post Re: ESAB Bantam TBH 140 Welder Restoration
[Laboratories, Equipment and Tools]
rikkitikkitavi
February 21, 2024, 10:58:53 PM
post Re: LabCoatz Staccato QCW No straight sparks
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Admiral Aaron Ravensdale
February 21, 2024, 09:13:05 PM
post Re: LabCoatz Staccato QCW No straight sparks
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ZakW
February 21, 2024, 09:04:11 PM
post Re: LabCoatz Staccato QCW No straight sparks
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Admiral Aaron Ravensdale
February 21, 2024, 08:53:07 PM
post Re: LabCoatz Staccato QCW No straight sparks
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ZakW
February 21, 2024, 07:48:47 PM
post Re: LabCoatz Staccato QCW No straight sparks
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Admiral Aaron Ravensdale
February 21, 2024, 07:28:29 PM
post Re: LabCoatz Staccato QCW No straight sparks
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ZakW
February 21, 2024, 06:58:39 PM
post LabCoatz Staccato QCW No straight sparks
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Admiral Aaron Ravensdale
February 21, 2024, 02:31:59 PM
post UD2.7 Thru Hole Capacitor Selection
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Saattvik24
February 21, 2024, 02:30:10 PM
post Re: DIY X-RAY generator made of eBay parts
[X-ray]
PhotonLab
February 20, 2024, 03:14:58 PM
post Re: DIY X-RAY generator made of eBay parts
[X-ray]
alan sailer
February 19, 2024, 06:08:05 PM
post Re: Ramped DRSSTC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
alan sailer
February 19, 2024, 03:03:37 PM
post Re: ZCS for SSTC without E class??
[Solid State Tesla Coils (SSTC)]
AstRii
February 19, 2024, 04:34:22 AM
post Re: ZCS for SSTC without E class??
[Solid State Tesla Coils (SSTC)]
davekni
February 19, 2024, 04:27:28 AM
post Re: ZCS for SSTC without E class??
[Solid State Tesla Coils (SSTC)]
AstRii
February 19, 2024, 03:59:51 AM
post Re: ZCS for SSTC without E class??
[Solid State Tesla Coils (SSTC)]
davekni
February 19, 2024, 03:45:51 AM
post Re: Ramped DRSSTC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
February 19, 2024, 03:30:09 AM
post Re: ZCS for SSTC without E class??
[Solid State Tesla Coils (SSTC)]
AstRii
February 19, 2024, 02:38:49 AM
post Re: Ramped DRSSTC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
alan sailer
February 19, 2024, 01:52:20 AM
post Re: Lathe Restauration
[General Chat]
TMaxElectronics
February 19, 2024, 12:47:27 AM
post Re: VS-GP250SA60S IGBT suitability - no flywheel diode
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
February 18, 2024, 10:32:36 PM
post Re: Ramped DRSSTC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
February 18, 2024, 10:06:58 PM
post Re: VS-GP250SA60S IGBT suitability - no flywheel diode
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Hydron
February 18, 2024, 11:43:44 AM
post Re: VS-GP250SA60S IGBT suitability - no flywheel diode
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Keybored
February 18, 2024, 03:41:12 AM
post Re: Ramped DRSSTC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
alan sailer
February 18, 2024, 02:43:37 AM
post Re: Ramped DRSSTC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ZakW
February 17, 2024, 10:45:17 PM
post Re: Ramped DRSSTC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
alan sailer
February 17, 2024, 10:29:30 PM
post Re: RDRSSTC - Project Build
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ZakW
February 17, 2024, 10:20:39 PM
post Re: Ramped DRSSTC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ZakW
February 17, 2024, 10:14:20 PM
post Re: RDRSSTC - Project Build
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
February 17, 2024, 08:56:42 PM
post Re: Ramped DRSSTC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
February 17, 2024, 08:52:45 PM
post Re: DIY X-RAY generator made of eBay parts
[X-ray]
PhotonLab
February 16, 2024, 09:20:44 AM
post Re: RDRSSTC - Project Build
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ZakW
February 16, 2024, 03:50:58 AM
post Re: Ramped DRSSTC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
alan sailer
February 16, 2024, 03:27:18 AM
post Re: DIY X-RAY generator made of eBay parts
[X-ray]
klugesmith
February 16, 2024, 01:55:48 AM
post Re: RDRSSTC - Project Build
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
February 15, 2024, 07:11:20 PM
post Re: DIY X-RAY generator made of eBay parts
[X-ray]
PhotonLab
February 15, 2024, 11:31:42 AM
post Re: ZCS for SSTC without E class??
[Solid State Tesla Coils (SSTC)]
davekni
February 15, 2024, 06:01:49 AM
post Re: ZCS for SSTC without E class??
[Solid State Tesla Coils (SSTC)]
AstRii
February 15, 2024, 05:13:13 AM
post Re: ZCS for SSTC without E class??
[Solid State Tesla Coils (SSTC)]
davekni
February 15, 2024, 04:26:00 AM
post Re: RDRSSTC - Project Build
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ZakW
February 14, 2024, 06:25:45 PM
post Re: DIY X-RAY generator made of eBay parts
[X-ray]
Luca c.
February 14, 2024, 03:33:25 PM
post Re: ZCS for SSTC without E class??
[Solid State Tesla Coils (SSTC)]
AstRii
February 14, 2024, 12:57:01 PM
post Re: RDRSSTC - Project Build
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
February 14, 2024, 05:32:30 AM
post Re: ZCS for SSTC without E class??
[Solid State Tesla Coils (SSTC)]
davekni
February 14, 2024, 05:22:35 AM
post Re: VS-GP250SA60S IGBT suitability - no flywheel diode
[Dual Resonant Solid State Tesla coils (DRSSTC)]
AstRii
February 14, 2024, 04:34:14 AM
post Re: VS-GP250SA60S IGBT suitability - no flywheel diode
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Keybored
February 14, 2024, 03:02:16 AM
post Re: RDRSSTC - Project Build
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ZakW
February 14, 2024, 01:58:17 AM
post Re: ZCS for SSTC without E class??
[Solid State Tesla Coils (SSTC)]
AstRii
February 13, 2024, 09:30:40 PM
post DIY X-RAY generator made of eBay parts
[X-ray]
PhotonLab
February 13, 2024, 03:54:23 PM
post VS-GP250SA60S IGBT suitability - no flywheel diode
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Keybored
February 13, 2024, 09:57:12 AM
post Re: TNY265 flyback issue
[Transformer (Ferrite Core)]
davekni
February 13, 2024, 03:50:05 AM
post Re: TNY265 flyback issue
[Transformer (Ferrite Core)]
AstRii
February 12, 2024, 07:30:42 PM
post Re: PLL "IHFSSTC" concept and schematic
[Solid State Tesla Coils (SSTC)]
Anders Mikkelsen
February 11, 2024, 10:30:38 PM
post Re: Help finding correct IGBT Module
[General Chat]
rikkitikkitavi
February 11, 2024, 09:41:57 PM
post Re: PLL "IHFSSTC" concept and schematic
[Solid State Tesla Coils (SSTC)]
Lucasww
February 11, 2024, 06:34:35 AM
post Re: TNY265 flyback issue
[Transformer (Ferrite Core)]
davekni
February 10, 2024, 03:55:35 AM
post Help finding correct IGBT Module
[General Chat]
cnichols
February 09, 2024, 09:34:13 PM
post TNY265 flyback issue
[Transformer (Ferrite Core)]
AstRii
February 09, 2024, 06:45:46 PM
post Re: Help Sourcing or Debugging My Small HV Module
[Transformer (Ferrite Core)]
michaelrcolton
February 08, 2024, 07:04:07 PM
post ESAB Bantam TBH 140 Welder Restoration
[Laboratories, Equipment and Tools]
Mads Barnkob
February 08, 2024, 06:47:35 PM
post Re: Anyone used iCCFL.com?
[Transformer (Ferrite Core)]
FPS
February 08, 2024, 12:27:47 AM
post Re: PLL "IHFSSTC" concept and schematic
[Solid State Tesla Coils (SSTC)]
Anders Mikkelsen
February 07, 2024, 09:49:11 PM
post Re: Anyone know of a good variable driver?
[Beginners]
NyaaX_X
February 07, 2024, 04:48:02 PM
post Re: Anyone know of a good variable driver?
[Beginners]
FPS
February 07, 2024, 08:17:37 AM
post Re: How much power?
[Spark Gap Tesla Coils (SGTC)]
Terry
February 06, 2024, 10:51:35 PM
post Re: OCXO Reference devolopment - or a story about scaleability
[Radio Frequency]
Mads Barnkob
February 06, 2024, 07:29:29 PM
post Re: Anyone used iCCFL.com?
[Transformer (Ferrite Core)]
MRMILSTAR
February 05, 2024, 05:18:33 AM
post Re: Anyone know of a good variable driver?
[Beginners]
Mads Barnkob
February 04, 2024, 09:16:25 PM
post Re: PLL "IHFSSTC" concept and schematic
[Solid State Tesla Coils (SSTC)]
davekni
February 04, 2024, 09:13:36 PM
post Anyone used iCCFL.com?
[Transformer (Ferrite Core)]
FPS
February 04, 2024, 09:00:30 PM
post Re: Anyone know of a good variable driver?
[Beginners]
FPS
February 04, 2024, 08:56:14 PM
post Re: OCXO Reference devolopment - or a story about scaleability
[Radio Frequency]
Da_Stier
February 04, 2024, 08:18:01 PM
post Re: Anyone know of a good variable driver?
[Beginners]
Mads Barnkob
February 04, 2024, 08:04:36 PM
post OCXO Reference devolopment - or a story about scaleability
[Radio Frequency]
Da_Stier
February 04, 2024, 07:56:55 PM
post Re: PLL "IHFSSTC" concept and schematic
[Solid State Tesla Coils (SSTC)]
Lucasww
February 04, 2024, 08:45:53 AM
post Anyone know of a good variable driver?
[Beginners]
FPS
February 04, 2024, 12:56:52 AM
post Re: looking for a pll sstc schematic with gate driver ic.
[Solid State Tesla Coils (SSTC)]
yourboi
February 03, 2024, 07:01:12 PM
post Re: SSTC bus inductance
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
February 03, 2024, 08:04:29 AM
post Re: SSTC bus inductance
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
February 03, 2024, 06:01:12 AM
post Re: is there a standard pinout of optical audio output connectors?
[Electronic Circuits]
Rafft
February 02, 2024, 05:04:44 PM
post SSTC bus inductance
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Benjamin Lockhart
February 02, 2024, 08:34:56 AM
post Re: How much power?
[Spark Gap Tesla Coils (SGTC)]
klugesmith
February 01, 2024, 07:03:41 PM
post Does anyone have a 3d print form for a spiral primary on 4" pvc?
[Solid State Tesla Coils (SSTC)]
yourboi
February 01, 2024, 06:23:45 PM
post Re: How much power?
[Spark Gap Tesla Coils (SGTC)]
Mads Barnkob
February 01, 2024, 07:53:53 AM
post Re: How much power?
[Spark Gap Tesla Coils (SGTC)]
klugesmith
January 31, 2024, 11:43:32 PM
post Re: Welcome new members, come say hello and tell a little about yourself :)
[General Chat]
Ranni81
January 31, 2024, 08:03:40 PM
post Re: How much power?
[Spark Gap Tesla Coils (SGTC)]
Hysteresis
January 31, 2024, 03:34:48 PM
post Re: How much power?
[Spark Gap Tesla Coils (SGTC)]
MRMILSTAR
January 31, 2024, 05:08:10 AM
post Re: How much power?
[Spark Gap Tesla Coils (SGTC)]
Mads Barnkob
January 30, 2024, 10:17:45 PM
post How much power?
[Spark Gap Tesla Coils (SGTC)]
Terry
January 30, 2024, 08:07:39 PM
post Ultrasonic Plastic Welding experiments with TA-40CS transducer
[Transformer (Ferrite Core)]
davekni
January 28, 2024, 11:37:30 PM
post Re: is there a standard pinout of optical audio output connectors?
[Electronic Circuits]
yourboi
January 28, 2024, 03:07:12 AM
post Re: First time DRSSTC Build
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Saattvik24
January 27, 2024, 02:27:29 PM
post Re: Lathe Restauration
[General Chat]
Mads Barnkob
January 27, 2024, 01:26:34 PM
post Re: Determine output voltage of DRSSTC
[General Chat]
Mads Barnkob
January 27, 2024, 01:15:51 PM
post Re: is there a standard pinout of optical audio output connectors?
[Electronic Circuits]
Mads Barnkob
January 27, 2024, 01:13:29 PM
post Determine output voltage of DRSSTC
[General Chat]
Pavol
January 27, 2024, 11:35:35 AM

Sitemap 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 
SimplePortal 2.3.6 © 2008-2014, SimplePortal