Author Topic: DRSSTC trouble  (Read 356 times)

Offline buchtawill

  • High Voltage Enthusiast
  • *
  • Posts: 4
  • Karma: +0/-0
    • View Profile
DRSSTC trouble
« on: November 30, 2020, 08:53:00 PM »
Hi all,
I am a high school senior in the US and I started making a DRSSTC back in January 2020, taking inspiration from Mads' DRSSTC I. I made the oneTesla kit a number of years ago and decided to come back to the wonderful land of Tesla coils. I have also made a spark gap tesla coil, which can be seen off to the right in the video below. Working on and off during the coronavirus lockdown, I had my first successful test last month (200VDC bus from variac):
It blew right after I took this video, which I attribute to my poor bridge design: https://drive.google.com/file/d/1YcG2pWm8kf7eFIVq646JIEfXXsDc9pin/view?usp=sharing. Whole rat's nest of wires. I have since remade the bridge with IXXN110N65C IGBTs and busbar, found here: https://drive.google.com/file/d/1Ah39WuPqT2fYzhU6FvLrx1yl8nClExOo/view?usp=sharing. Since making the new bridge, I have not been able to get it running. New MMC is 3x7 CDE942C20P15 for 0.35uF @ 6KVDC, or around 900VAC derated @74kHz. Bus is 15,000uF 400V Kemets(2 x 7,500). Driver board is a variant of oneTesla's: https://drive.google.com/file/d/1pFHJJzeRBw8jN1Er48E7NNonjFVLksk1/view?usp=sharing. I use a 15v 1:1:1:1:1 GDT, something I plan to change in the future. I also added an OCD circuit after blowing the first set of IGBTs, which is not shown on the schematic. For an interrupter, I used oneTesla's SD interrupter. It's designed for much smaller coils, so I plan on modifying that in the future as well, but it works for now.

After firing up the new coil last night, no sparks flew. I have been stuck scratching my head. I was running with 130VDC from a variac. I tried flipping the feedback CT, but still no luck. I did notice, however, that the MMC gets charged, which is curious (After signaling the coil to fire and nothing happened, I shut everything down and measured a quickly declining voltage across the MMC). Any thoughts/comments/suggestions on what to try next? If you have any clarifying questions, please let me know and I'll try to get back ASAP.

Offline davekni

  • High Voltage Senior
  • *****
  • Posts: 865
  • Karma: +40/-0
  • Physicist, engineer (electronic), and hobbiest
    • View Profile
Re: DRSSTC trouble
« Reply #1 on: December 01, 2020, 12:02:23 AM »
Likely not your initial issue, but it's better to have CT (current transformer) on one of the two H-Bridge outputs, not after the MMC.  After the MMC is several kV, so can cause corona and insulation failure eventually.

The schematic you reference looks like a design for antenna feedback.  DRSSTCs need primary current feedback.

Do you have an oscilloscope?  It's very difficult to diagnose issues without one.
David Knierim

Offline buchtawill

  • High Voltage Enthusiast
  • *
  • Posts: 4
  • Karma: +0/-0
    • View Profile
Re: DRSSTC trouble
« Reply #2 on: December 01, 2020, 02:00:54 AM »
Hi davekni,
Thanks for the reply. The driver circuit does use primary feedback, H3 and H4 are connections to a 33:33:1 cascaded transformer. I borrowed it from oneTesla, which also employs primary feedback. That being said, I am open to redesigning it/moving towards a UD2 type controller. I will move the CTs for my next test. I do, thankfully, have an oscilloscope which I can use, but I am nervous about putting it near something like a Tesla coil while in operation. It would definitely be useful to see GDT output on top of primary current. Anything else I should measure for the next test?

Offline davekni

  • High Voltage Senior
  • *****
  • Posts: 865
  • Karma: +40/-0
  • Physicist, engineer (electronic), and hobbiest
    • View Profile
Re: DRSSTC trouble
« Reply #3 on: December 01, 2020, 03:46:10 AM »
H3 and H4 feed a circuit typical of antenna feedback.  It is not a suitable load for the CT.  Yes, clone the input part of UD2.7.  Or, here's a variation I prefer:


For schematics such as yours that don't need both comparator outputs, I prefer TLV3501 for its rail-to-rail input range.  Also, the above circuit is weakly self-oscillating.  That guarantees startup no matter what initial state the H-Bridge outputs may be in.  (With UD2.7, a bleed-resistor across the H-Bridge outputs or other way to initialize state is needed for reliable startup.)  The only nuisance with the above circuit is that C1 and C2 need to be scaled to roughly match your operating frequency.  Above values self-oscillate at roughly 130kHz.  Scale caps by 1/frequency.  Doesn't need to be precise.  Even if self-oscillation is at half of operating frequency it will work.

Another detail in your schematic:  The GDT coupling capacitor C10 doesn't have any damping (additional R and C) as in the UD2.7 schematic.  That may be OK, but can cause trouble with the resulting low-frequency series resonance of C10 and GDT inductance.

Yes, scoping IGBT gate waveforms is helpful, as is scoping H-Bridge outputs.  This is if you have an isolated power supply for the H-Bridge or a differential probe.  If neither is an option, then at least scope the driver output (input to GDT) and current feedback.
David Knierim

Offline buchtawill

  • High Voltage Enthusiast
  • *
  • Posts: 4
  • Karma: +0/-0
    • View Profile
Re: DRSSTC trouble
« Reply #4 on: December 02, 2020, 02:43:33 AM »
Hello once again,

Success! Or at least somewhat. I moved the OCD and feedback CTs to before the cap bank as you suggested. I ran a test with 190VDC bus (I think part of my problem the other day was a too low bus voltage) and got sparks so small I could only hear them, not see them. Please note that the resonance is ballpark tuned (10% lower than secondary rule), I still need to do fine adjustments. After this somewhat successful test, I tried playing with my OCD circuit. I raised the threshold a little and saw negligible effects, and proceeded to disconnect the OCD CT entirely. Here are my results:
So the pros: it works with decent sized arcs
Cons: There is something wrong with my OCD circuit
Any tips or tricks for OCD? I borrowed the OCD circuit chunk from https://www.stevehv.4hv.org/DRSSTC1/DRSSTC1OCDsch.JPG. My connection to the transformer is pretty long, there may be some issues with noise.

« Last Edit: December 02, 2020, 03:13:20 AM by buchtawill »

Offline davekni

  • High Voltage Senior
  • *****
  • Posts: 865
  • Karma: +40/-0
  • Physicist, engineer (electronic), and hobbiest
    • View Profile
Re: DRSSTC trouble
« Reply #5 on: December 02, 2020, 03:29:14 AM »
Use Steve's feedback circuit as well as OCD.  The feedback circuit you showed previously is for antenna input.  Better, use a UD2.7-style feedback which has phase-lead (or the variation I posted earlier).  Phase lead will reduce stress on IGBTs, making them more robust to poor bridge layout (parasitic wiring inductance).

The wrong feedback circuit w/o CT load is the most likely cause of OCD issues.

If capacitively-coupled noise is the issue, increase C15 from 1nF to something larger.  100nF should still respond plenty quickly, but provide much more noise immunity.
« Last Edit: December 02, 2020, 03:41:09 AM by davekni »
David Knierim

High Voltage Forum

Re: DRSSTC trouble
« Reply #5 on: December 02, 2020, 03:29:14 AM »

 


* Recent Topics and Posts

post Re: Blackbody Radiation and Thermal Control of Satelites.
[General Chat]
klugesmith
Today at 10:18:13 PM
post Re: Next Gen DRSSTC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
TMaxElectronics
Today at 10:13:16 PM
post Re: 833A Maximum Dissipation Ratings
[Vacuum Tube Tesla Coils (VTTC)]
kyledellaquila
Today at 07:11:20 PM
post 833A Cathode Modulation
[Vacuum Tube Tesla Coils (VTTC)]
kyledellaquila
Today at 07:09:52 PM
post GU5B VTTC Flashover
[Vacuum Tube Tesla Coils (VTTC)]
SalinsLV
Today at 03:01:46 PM
post Re: compact midi interrupter
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
TMaxElectronics
Today at 12:57:53 PM
post Re: Enclosure design considerations for a DRSSTC?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
GrantV
Today at 10:26:15 AM
post Re: Enclosure design considerations for a DRSSTC?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
acobaugh
Today at 06:09:48 AM
post Blackbody Radiation and Thermal Control of Satelites.
[General Chat]
Patrick
Today at 03:57:45 AM
post Re: Self Oscillating Half Bridge Wonder
[Solid State Tesla Coils (SSTC)]
kyledellaquila
January 23, 2021, 07:22:57 PM
post Re: compact midi interrupter
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
octopus1
January 23, 2021, 07:15:46 PM
post Re: Self Oscillating Half Bridge Wonder
[Solid State Tesla Coils (SSTC)]
Magneticitist
January 23, 2021, 06:54:18 PM
post Re: compact midi interrupter
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
Mads Barnkob
January 23, 2021, 06:39:16 PM
post Re: 833A Maximum Dissipation Ratings
[Vacuum Tube Tesla Coils (VTTC)]
kyledellaquila
January 23, 2021, 05:43:59 PM
post Re: Self Oscillating Half Bridge Wonder
[Solid State Tesla Coils (SSTC)]
Acid Byte
January 23, 2021, 03:40:18 PM
post Re: Next Gen DRSSTC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
pc50kd
January 23, 2021, 02:35:18 PM
post Re: New projet OmegaDR
[Dual Resonant Solid State Tesla coils (DRSSTC)]
paulj
January 23, 2021, 11:27:50 AM
post 8 ft spark french tesla coil
[Spark Gap Tesla Coils (SGTC)]
paulj
January 23, 2021, 11:00:37 AM
post Re: High voltage transformer for neon bombarding.
[Transformer (Iron Core)]
klugesmith
January 22, 2021, 11:23:39 PM
post Re: Paralleling IGBT bricks for H-bridge
[Solid State Tesla Coils (SSTC)]
davekni
January 22, 2021, 08:09:18 PM
post Re: ZVS driven Plasma Ball (w/ segmented PTFE Secondary)
[Transformer (Ferrite Core)]
zytra
January 22, 2021, 06:49:26 PM
post Re: High voltage transformer for neon bombarding.
[Transformer (Iron Core)]
AndreasVE
January 22, 2021, 11:16:43 AM
post Enclosure design considerations for a DRSSTC?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
GrantV
January 22, 2021, 10:05:28 AM
post Re: Paralleling IGBT bricks for H-bridge
[Solid State Tesla Coils (SSTC)]
Patrik
January 22, 2021, 08:47:11 AM
post Re: Paralleling IGBT bricks for H-bridge
[Solid State Tesla Coils (SSTC)]
davekni
January 22, 2021, 06:19:21 AM
post Re: ZVS driven Plasma Ball (w/ segmented PTFE Secondary)
[Transformer (Ferrite Core)]
davekni
January 22, 2021, 06:03:43 AM
post Re: induction heater issues
[Electronic Circuits]
davekni
January 22, 2021, 05:45:21 AM
post Re: Anybody got some tips for releasing a product?
[General Chat]
AeraCura_
January 22, 2021, 05:22:44 AM
post Re: Anybody got some tips for releasing a product?
[General Chat]
octopus1
January 22, 2021, 04:58:04 AM
post Re: compact midi interrupter
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
AeraCura_
January 22, 2021, 03:39:07 AM
post Re: induction heater issues
[Electronic Circuits]
petespaco
January 22, 2021, 03:18:53 AM
post Re: High voltage transformer for neon bombarding.
[Transformer (Iron Core)]
klugesmith
January 22, 2021, 01:52:12 AM
post Re: 833A Maximum Dissipation Ratings
[Vacuum Tube Tesla Coils (VTTC)]
kyledellaquila
January 22, 2021, 01:26:13 AM
post Re: induction heater issues
[Electronic Circuits]
aes92000
January 22, 2021, 01:19:24 AM
post Anybody got some tips for releasing a product?
[General Chat]
TMaxElectronics
January 22, 2021, 12:46:22 AM
post Re: compact midi interrupter
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
TMaxElectronics
January 22, 2021, 12:41:44 AM
post Paralleling IGBT bricks for H-bridge
[Solid State Tesla Coils (SSTC)]
Patrik
January 21, 2021, 02:10:48 PM
post Re: Welcome new members, come say hello and tell a little about yourself :)
[General Chat]
Patrik
January 21, 2021, 11:31:39 AM
post High voltage transformer for neon bombarding.
[Transformer (Iron Core)]
AndreasVE
January 21, 2021, 10:53:15 AM
post Re: ZVS driven Plasma Ball (w/ segmented PTFE Secondary)
[Transformer (Ferrite Core)]
zytra
January 21, 2021, 08:36:50 AM
post Re: induction heater issues
[Electronic Circuits]
davekni
January 21, 2021, 05:10:27 AM
post Re: 4HV gone?
[General Chat]
Patrick
January 21, 2021, 05:08:54 AM
post induction heater issues
[Electronic Circuits]
aes92000
January 21, 2021, 04:19:43 AM
post Re: Help for people buying the "12-48 Volt 1800/2500 Watt ZVS induction Heater"
[Electronic Circuits]
hightemp1
January 21, 2021, 03:00:50 AM
post Re: ZVS driven Plasma Ball (w/ segmented PTFE Secondary)
[Transformer (Ferrite Core)]
zytra
January 21, 2021, 02:21:32 AM
post Re: ZVS driven Plasma Ball (w/ segmented PTFE Secondary)
[Transformer (Ferrite Core)]
davekni
January 21, 2021, 01:23:12 AM
post Re: ZVS driven Plasma Ball (w/ segmented PTFE Secondary)
[Transformer (Ferrite Core)]
zytra
January 21, 2021, 01:12:01 AM
post Re: Weird optocoupler in guitar amplifier
[Electronic Circuits]
davekni
January 20, 2021, 11:51:48 PM
post Re: ZVS driven Plasma Ball (w/ segmented PTFE Secondary)
[Transformer (Ferrite Core)]
davekni
January 20, 2021, 11:47:09 PM
post Re: Weird optocoupler in guitar amplifier
[Electronic Circuits]
TMaxElectronics
January 20, 2021, 11:19:41 PM

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