Show Posts

This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.


Topics - Hydron

Pages: [1]
1
I've just finished laying out a couple of boards for the bridge and gate drive of my larger 160mm DRSSTC which I'll be upgrading when I'm in NZ over the (southern) summer. These may be of interest to others, so I've uploaded all the design files to github, and also put a couple of 3d renders below:

https://github.com/Hydron-4hv/Big_DRSSTC_Bridge_PCBA

https://github.com/Hydron-4hv/Big_DRSSTC_Gate_Drive_PCBA


Notes:
- Github README has the majority of explanation in it
- The schematic pdfs have a 3d model in them, open with acrobat reader to view
- Original files are in Altium format, I may be able to export to something else if needed (KiCAD is unlikely though, sorry!)

I'd welcome any suggestions/criticism, these are going off to JLCPCB in the next few days and obviously I'd like them to be correct!

I may have some more PCBs coming up too, but they are likely to to be more specific to my design (though I will share them anyway).

2
Just a quick post to share a trick I found useful for replacing a BNC connector without rear access on a Model 4100 Pearson "Wideband Current Monitor" (internally terminated wideband CT).

These items are made with a brass case surrounding the CT core, and are 100% epoxy potted _after_ the BNC connector is screwed to the case and it's centre pin soldered to the CT output. They are then dipped in (green) paint. See below for an undamaged example:

Example of the type of BNC used:

The actual part number seems to be a UG-290A/U Amphenol RF 50R BNC, but there are equivalent (cheaper, non MIL-Spec) parts widely available with the same dimensions, including the B6551A1-NT3G-50 I used in my repair.

I obtained one of these CTs on ebay for a steal, but it came with a badly damaged (dented, deformed) BNC. While I was able to beat it back into enough shape to work with some BNC connectors, it was still a problem with most of my cables/connectors, so a solution was desirable.

Although the paint covering the base of the BNC can be removed to access the screws and free the base from the unit, the centre pin is still soldered to a wire trapped by epoxy, so the connector cannot be removed. Brute force could be tried to pull the connector off (leaving the pin behind) but risks breaking internal connections. Thankfully I found another way!

It turns out that it's possible to "remotely" de-solder the wire at the back of a BNC socket by heating up a conductive pin inserted into the front. I found a diode with thick copper legs that _just_ fit into the front socket, and cut one off to use. Heated with a soldering iron set to ~325C and placed just above where the copper pin entered the insulator inside the BNC, it managed to desolder the pin at the back and allow the BNC to be removed. This was probably helped by teflon's high temperature resistance (~350C melting) and the leaded solder used in the old CT, but can probably still be done for lead-free by using a higher temperature and accepting that the insulator may melt and make a mess (not a big issue as that part is being replaced anyway).

Behind the BNC was bare brass with tapped holes at the corners and a hole milled through for the central protrusion and connection (sorry forgot to take a pic of this). Epoxy potting compound had surrounded the space where the rear protrusion of the BNC had been, with the termination wire down a little hole formed by the removal of the central pin. After checking that the new BNC would fit (the rear insulator was thankfully the exact same diameter, and slightly shorter) I sanded down the pin at the back of the new BNC to match the (slightly shorter) pin of the old one, and also opened up the solder cup a bit.

At this point I had two options - do the de-solder trick in reverse to solder the connection again from the front with the new BNC (I tested this on a scrap BNC, and it worked without melting the insulator with a 325C iron and leaded solder), or remove the new BNC pin from the connector and fit it separately. With a teflon insulator the pin could be pressed out relatively easily (it's not actually meant to be removed!), and as the bottom of the hole with the CT termination wire was full of epoxy (i.e. strong enough to withstand the BNC connector being pushed back onto the central pin), I decided to solder the pin on first, then push the BNC back onto it. This step was fairly easy - I was just careful that the pin was straight and at the right height, and got a fine tipped iron into the base to hit both the end of the termination wire and the solder cup for a nice solid joint. The BNC shell was aligned to match the screw holes and pressed onto the pin (alignment is critical, as twisting or pulling after the fact to line things up is risky!). Finished result along with the old bent BNC is shown below - good as new:


...uh, I take back the description of "quick post", but hopefully this trick can help others with a similar problem!

3
As part of the design process for my (under construction) QCW coil I took a long look at the different TO-247 (and similar) IGBTs available, and ended up deciding to buy some FGA60N65SMD parts from Mouser, with FGY75N60SMDs coming in as a second choice, mainly due to significantly increased cost. The criteria and pros/cons I used to decide this are quoted below from one of my 4hv posts (see http://4hv.org/e107_plugins/forum/forum_viewtopic.php?180799.0#post_180879 for full thread context):

Quote
I have just ordered a bunch of FGA60N65SMDs myself after quite a lot of comparison and evaluation.

I had the following wish list when picking IGBTs:
- Reasonable Qg to make driving at 350kHz for 10-15ms at a time not too difficult
- Fast, with low Eoff (will be some hard switching - OFF only - in QCW)
- Cheap (am running multiple parallel bridges, so needed a few!)
- Low Rjc to keep die temperature swing down

After hours of searching I ended up back where I started - overall the standard choice of 60N65s(/60N60s) were the best option, and are well tested. Second pick was the FGY75N60SMD, with the following pros/cons compared to the 60N6x parts:

Cons:
- about 50% more expensive
- more Qg (though not excessive)
- slightly higher Eoff per amp, though significantly lower fall time, so a little dubious about how much difference there really is here
- no mounting hole for those who need this (am using clips so I don't care)
- no 650V rated option, only 600V (though I suspect the 600 vs 650 is mostly packaging related, and can likely be disregarded)

Pros:
- no mounting hole to reduce heatsink contact area
- lower Rjc thermal impedance, especially for the co-pack diode (which has less than half of the 60N65 value). Diode is only important if using freewheeling or phase shift QCW
- maybe easier to find?

I was very close to getting the 75N60s, mainly due to the thermal impedance stuff, as I plan to use the freewheeling diode quite a bit for phase shift QCW modulation. In the end the 60N65 seemed likely to be good enough, and if I have issues then there's still an upgrade path!

As a heads up, stock seems to be a bit scarce of some of these parts - Mouser had the best price on the 60N65s so I bought from them, but they only have 11 left now and a 1 YEAR lead time on more!

The Mouser stock of 11 mentioned is now completely gone, but as suggested by loneoceans, it's also worth checking the other more wholesale orientated distibutors like Arrow/AVNET too for this sort of thing (I would have saved about 10% had I done so).

This brings me to the Aliexpress part of the story - having ordered a bunch of legitimate 60N65s, I thought I'd look on Aliexpress to see if there were any suspiciously cheap 75N60s to buy as a second option :P

Playing Aliexpress roulette with the larger 75N60 parts vs 60N60/60N65s seemed to have a few pros/cons:

- Fewer sellers of the larger parts mean it's easier to sort through the options, but less choice of sellers/quantities/prices
- There aren't any really cheap "Power TO247" parts that could be relabeled for a counterfeit 75N60, compared to the much more common TO-247/TO-3P packages used by the 60N6x parts. Anything that actually has a real IGBT die inside should have a current rating at least as high as a 75N60, and there's probably not much to be gained by swapping something else for what is one of the smaller/cheaper Power-TO247 parts.

Sorting the options down to sellers that:
a) Had a picture of the real part, not something with the Fairchild "F" missing or just a completely different package
b) Offered singles or small lots (up to 10 parts) at a reasonable price & shipping rate
Gave 2-3 options of sellers to purchase from.

In the end I chose these: https://www.aliexpress.com/item/10PCS-FGY75N60SMD-600V75A/32327762387.html because the seller had much more of a history than the others, with many positive reviews to go with a few bad ones complaining of fakes etc (of different products, not the 75N60s). Price ended up being 1.75 USD each, or about 30% of what I would have paid from the normal sources (e.g. Mouser, RS etc) - cheap but not so insane that it MUST be fake. US large quantity prices (without ~20% EU sales tax) are much closer to what I paid than what I could get buying 10 in Europe.

The 10 parts I ordered (1 lot) shipped within a few days, with the post taking about 2 weeks. When they arrived I noted the following:
a) All 10 were just thrown in a single (non-antistatic) bag inside the padded postal envelope. Some legs had minor bends and the epoxy of the packages had a fair number of light scratches in it, possibly from shipping with no protection from the other parts in the bag.
b) The packages exactly matched datasheet information with the exception that the legs were longer than specified.
c) No evidence of any sanding/grinding of the package for re-marking. All expected tooling marks were present, including moulded numbers/letters in one of the recesses.
d) Laser engraving of part number exactly matched that of other Fairchild/ONsemi IGBTs I have, e.g. shape of letters, where the laser started/stopped (see pic)
e) Testing all 10 using a multi-meter showed expected behavior of an IGBT - 1 diode drop when measured backwards, open-circuit in forward direction until the gate is charged at which point they showed approx. 1 diode drop in that direction too.

So far so good!

For thoroughness I wanted to do a couple of extra tests. The first was to sacrifice a part to mechanically decap and check that die size was realistic. I was very happy to find that searching for "FGY75N60SMD die size" gives the bare die datasheet: https://shop.micross.com/pdf/fairchild/igbt/FGY75N60SM_IGBT_DIE.pdf as the first result; exactly what I needed to comprehensibly confirm that the parts I'd ordered were real, or at least QC rejects, rather than a completely different part. Grinding down the package revealed a large IGBT die of the exact dimensions given in the bare die datasheet, along with a smaller diode die. The diode die was much thicker than the IGBT, which also meets the expectations of a "Field Stop" IGBT die, which is significantly thinner than the original wafer (75 microns in this case).

I also used a "Megger" to test the parts for OFF-state leakage at up to 650V, getting much less than the datasheet value of 250uA (cannot remember exact value, but may have been in the single digit uA).

Finally I put them in a half bridge and ran them up to ~150A peak current. No smoke was emitted, and the gate charge times were approximately double those of the FGH40N60SMDs I was comparing to, which matches the gate charge increase between the 40N60 and 75N60 parts. Soft switching times were significantly slower on the larger parts, but hard switching was much closer, so everything seems correct.

I have subsequently bought 20 more parts from the same seller, and they seem physically identical to the first lot, and multi-meter test passes as well, though I have not done any other testing. Obviously I cannot tell whether the seller will continue to supply real parts or not, but at under $2 each (less when the seller has a sale) they might be worth the risk!

Hopefully the info about what I bought and the tests I did will be of use to others tempted by cheap deals on Aliexpress/Ebay - I know there are a lot of fakes out there but it seems that I got lucky this time!

Shown in the scan below are a number of the 75N60 parts (included the one I ground down to show the die), along with some 40N60 and 60N65 parts for comparison.

4
Rather a long time ago (2014) I took some interesting measurements of the topload and breakout point current in a medium sized (160mm/6" secondary) DRSSTC at a number of different power levels.

I was always intending to do some post processing on the data to learn more about streamer/arc impedance and topload conditions during a burst, but never ended up having the motivation/time to do so (the idea was to use it as an excuse to learn some python coding skills!). I think it's about time I put this data out in the public for all to have a look at, with the hope that some find it interesting and that it helps us learn more about tesla coil physics.

The other reason to get this out there now is that I'm forgotting some important details about the coil which was measured, as I've been living on the other side of the world from it since these measurements were taken and my notes at the time were limited. I unfortunately can't verify coil parameters or repeat the measurements with more documentation until at least next April. That said, the coil specs I have are as follows:


DRSSTC specs, info:

Secondary: 160mm dia, ~730mm winding length (see attached JavaTC file for more accurate numbers), 1920 turns of 0.315mm dia. wire
Toroid: ~170mm minor diameter, ~760mm major diameter (as above, see attached JavaTC file). Constructed of aluminium ducting.
Primary: 11 turns of 6.35mm dia. copper tube, spaced approx 15mm centre-centre, starting at approx 200mm diameter
Tank capacitor: 48x 2uF 1000V Aerovox snubbers, in 2 parallel strings of 24. Tappable for a range of ~400-166nF at 10-24kV (I believe these tests were at the lower end of this range, likely at 166-200nF)
Coupling: approx 0.15 (adjustable)
IGBTs: 2x CM300DY-24H, ~750A OCD setting
Bus capacitance: 2x4700uF in series
Rectifier: Voltage doubler
Variac: 15A, ~0-260V output
Driver: DIY design based on UD2.5. Can be assumed to be equivalent to any UD2.x design.
Interrrupter: DIY design based on oneTesla midi interrupter code.

The coil is not too sensitive to tuning, and runs happily on both upper and lower pole tuning. I find that with the >600V available with the voltage doubler rectifier that upper pole tuning with higher-Z primary gives nicer, more controllable streamers, especially when playing MIDI music with the coil. I also tried lower pole tuning with a lower impedance primary setup and non-doubler rectifier - this also gave good streamer length but they were more "chaotic", MIDI did not work as well and streamer length was much more sensitive to coil input power.

I've attached a few pictures of the coil in action, with some ground strikes in the ~1.5-2m range. Max strike length achieved is almost 2.5m, or a little over 3x secondary wound length. I have not pushed it properly - the only part I've blown up on this coil was a plugpack supply that was hit by a streamer during the prototype phase!






Video taken while controlling coil - dont drive and film if you want quality!. I believe this was lower pole tuning.

Measurement info:

Scope:
- The topload current measurements were done using a Cleverscope CS328A PC based oscilloscope (see https://cleverscope.com/products/), with the ethernet interface option installed. This allowed me to power the scope and a wifi router off batteries, and locate them on the topload while maintaining control and data download capability remotely from my laptop.
- I've attached a picture of the first rough test setup - the wires were tidied up and the wirewound resistors were replaced for the actual measurements, but the idea remains the same.
- With 5.8GHz wifi, a faraday cage shield could be located over the test equipment, with only a small hole needed to get the wifi signal out, allowing it to be completely safe from the output voltage.
- A small DC offset may be present in the measurements due to non-perfect calibration of the scope - this probably should be removed before doing any calculations using the data.



Probing/measurement setup:
- A 1R resistor was placed in series with the connection from the top of the secondary to the toroid, and the 2R resistor placed in series with the toroid and the breakout point
- All measurements are of the voltages across these resistors, referenced to the toroid. As such, the voltage measured for the breakout current (channel B) is 2V/A and 180 degrees out of phase with the toroid current (channel A), which is 1V/A. Inverting and scaling by x0.5 will correct the channel B voltages and give the breakout point current at 1V/A - channel A data needs no modification and directly shows toroid input current at 1V/A.
- Scope was setup for 30ns between samples (i.e. 33MS/s), with a 20MHz bandwidth filter on both channels. As the input frequency is not expected to be high aliasing shouldn't be present, despite the nyquist sampling criteria not being met. The lowest power measurement was at a slightly slower sampling rate, 50ns between samples (20MSa/s), cant remember why sorry!

Coil operation during measurements:
- The topload currents were measured at 5 different power levels (file naming is related to the descriptions below, should be self-explanatory):
   - Very low power (no breakout)
   - Medium power (breakout into streamer, no ground strike)
   - Higher power (breakout into streamer, no ground strike)
   - Even higher power (small ground strike)
   - Highest power (big ground strike)
- In each case BPS was set to ~100, with power adjusted by changing variac output (and possibly the on-time, unfortunately I can't remember)
- For each power level, the first 100 on-periods from interrupter signal being applied were captured by using the segmented memory of the scope. This allowed for a reasonable sample rate (33MS/s) to be used by only capturing actual data, not the time when the interruptor was off. The number of captures (100 = 1 second at 100BPS) is enough to show the evolution of a streamer or ground strike in a way that a single capture cannot.
- Videos were captured for 3 of the 5 power levels, and can be found here:
I have the original video files if they are useful to anyone, but youtube is more convenient.
- A picture of the coil in it's measurement setup is attached below. The item seen on top of the topload is a plastic block I used to keep the faraday shielding in place.



Notes on captured data:
- All 500 waveform captures are found here, 7zipped up (7zip compressed them much better than plain zipping): https://highvoltageforum.net/files/hydron_topload_current_waveforms.7z
- Each is in a CSV type format (I think the delimiting character is a tab rather than comma), with a few lines of header at the start.
- The "TriggerTime" number is in days from a start-of-1900 epoch (unsure what time zone etc); the fractional part can be converted into seconds by multiplying by 24*60*60. Difference between sequential captures should be very close to 0.010 seconds (100BPS).
- Trigger point will unfortunately not be in exactly the same point every time, as it is triggering off input current which varies depending on power level. Enough pre-trigger data was captured however to show the start of every on-period.


Hopefully this data is of use/interest to some, and can be processed to learn more about the complex impedance of streamers during growth, which may allow for better design decisions to be made when building coils. Some things to remember while doing so:
- This only captures current flowing into the topload capacitance, not the secondary coil capacitance. JavaTC splits these out into separate numbers.
- The breakout point also has it's own additional capacitance to ground. This can be estimated by looking at the low power (i.e. before capacitive streamer forms) measurements of current flowing into it in comparison to the toroid current (which will be the sum of current due to both toroid and breakout capacitance).

Edit: see a couple of waveform captures below, showing raw data before scaling and inversion of channel B

Pages: [1]

* Recent Topics and Posts

post Re: My First DRSSTC
[Dual Resonant Solid State Tesla coils]
Hydron
Today at 11:07:22 AM
post Re: My First DRSSTC
[Dual Resonant Solid State Tesla coils]
sjsimmo
Today at 08:08:58 AM
post Re: How to calculate VA rating and other things for Ferrite Core? (SMPS)
[Transformer (ferrite core)]
sjsimmo
Today at 01:24:15 AM
post How to calculate VA rating and other things for Ferrite Core? (SMPS)
[Transformer (ferrite core)]
FilipŠebík
January 18, 2019, 07:32:38 PM
post Re: How to design a 7.5kV AC source?
[Transformer (ferrite core)]
profdc9
January 18, 2019, 04:25:14 PM
post How to design a 7.5kV AC source?
[Transformer (ferrite core)]
CristianM
January 18, 2019, 03:48:06 PM
post Re: Help for people buying the "12-48 Volt 1800/2500 Watt ZVS induction Heater"
[Electronic circuits]
the_anomaly
January 17, 2019, 02:01:36 AM
post Re: Help for people buying the "12-48 Volt 1800/2500 Watt ZVS induction Heater"
[Electronic circuits]
petespaco
January 16, 2019, 04:26:38 AM
post AC vs DC fuses, high current, explosive destructive testing and theory
[Capacitor banks]
Mads Barnkob
January 15, 2019, 09:48:48 PM
post Re: My X-Ray Machine
[X-ray]
neukyhm
January 15, 2019, 10:51:46 AM
post Re: Help for people buying the "12-48 Volt 1800/2500 Watt ZVS induction Heater"
[Electronic circuits]
petespaco
January 14, 2019, 05:08:38 PM
post Re: Help for people buying the "12-48 Volt 1800/2500 Watt ZVS induction Heater"
[Electronic circuits]
the_anomaly
January 14, 2019, 01:15:53 PM
post Re: Help for people buying the "12-48 Volt 1800/2500 Watt ZVS induction Heater"
[Electronic circuits]
Mads Barnkob
January 14, 2019, 12:22:07 PM
post Re: Help for people buying the "12-48 Volt 1800/2500 Watt ZVS induction Heater"
[Electronic circuits]
petespaco
January 11, 2019, 05:10:39 AM
post Re: My X-Ray Machine
[X-ray]
Max
January 10, 2019, 10:59:25 PM
post Re: 迎词、来
[General chatting]
profdc9
January 10, 2019, 06:56:59 PM
post Re: Help for people buying the "12-48 Volt 1800/2500 Watt ZVS induction Heater"
[Electronic circuits]
petespaco
January 10, 2019, 05:33:48 PM
post Re: Welcome new members, come say hello and tell a little about yourself :)
[General chatting]
black.yang
January 10, 2019, 02:11:58 AM
post Re: My X-Ray Machine
[X-ray]
Mads Barnkob
January 09, 2019, 09:14:59 PM
post Acoustic spectra of sung vowels by the FFT analyzer HP 3561A
[Electronic circuits]
Physikfan
January 08, 2019, 08:44:16 PM
post Re: IGBT failure in DRSSTC
[Dual Resonant Solid State Tesla coils]
Felix Bieri
January 08, 2019, 05:33:55 PM
post Re: Huawei RRU3928 1800MHz radio base station teardown (part 1 of 2)
[Radio frequency]
Mads Barnkob
January 08, 2019, 08:25:08 AM
post Re: SimpleDriver v2.3, my phase-shifting QCW DRSSTC controller
[Dual Resonant Solid State Tesla coils]
flyglas
January 08, 2019, 08:25:02 AM
post Re: SimpleDriver v2.3, my phase-shifting QCW DRSSTC controller
[Dual Resonant Solid State Tesla coils]
Hydron
January 08, 2019, 02:01:50 AM
post Re: (DR)SSTC II
[Dual Resonant Solid State Tesla coils]
Hydron
January 07, 2019, 10:23:38 PM
post Re: (DR)SSTC II
[Dual Resonant Solid State Tesla coils]
Laci
January 07, 2019, 08:53:32 PM
post Re: Help for people buying the "12-48 Volt 1800/2500 Watt ZVS induction Heater"
[Electronic circuits]
petespaco
January 07, 2019, 08:17:44 PM
post Re: SimpleDriver v2.3, my phase-shifting QCW DRSSTC controller
[Dual Resonant Solid State Tesla coils]
Netzpfuscher
January 07, 2019, 07:37:53 PM
post Re: (DR)SSTC II
[Dual Resonant Solid State Tesla coils]
Uspring
January 07, 2019, 01:30:36 PM
post Re: (DR)SSTC II
[Dual Resonant Solid State Tesla coils]
Laci
January 07, 2019, 12:43:26 PM
post Re: (DR)SSTC II
[Dual Resonant Solid State Tesla coils]
Hydron
January 07, 2019, 08:09:49 AM
post Re: SimpleDriver v2.3, my phase-shifting QCW DRSSTC controller
[Dual Resonant Solid State Tesla coils]
NEYi
January 07, 2019, 07:43:50 AM
post Re: Welcome new members, come say hello and tell a little about yourself :)
[General chatting]
Mads Barnkob
January 07, 2019, 06:48:06 AM
post Re: (DR)SSTC II
[Dual Resonant Solid State Tesla coils]
Mads Barnkob
January 07, 2019, 06:39:56 AM
post Re: (DR)SSTC II
[Dual Resonant Solid State Tesla coils]
Laci
January 06, 2019, 09:23:19 PM
post Re: Help for people buying the "12-48 Volt 1800/2500 Watt ZVS induction Heater"
[Electronic circuits]
petespaco
January 06, 2019, 07:11:25 PM
post Re: (DR)SSTC II
[Dual Resonant Solid State Tesla coils]
Uspring
January 06, 2019, 07:02:14 PM
post Re: (DR)SSTC II
[Dual Resonant Solid State Tesla coils]
flyglas
January 06, 2019, 12:43:46 PM
post Re: (DR)SSTC II
[Dual Resonant Solid State Tesla coils]
Laci
January 06, 2019, 11:55:09 AM
post Re: (DR)SSTC II
[Dual Resonant Solid State Tesla coils]
TDAF
January 06, 2019, 09:48:06 AM
post Re: First SSTC build, need help troubleshooting
[Solid state Tesla coils]
TDAF
January 06, 2019, 09:45:17 AM
post 关于: 这个便宜的 drsstc 驱动程序从 aliexpress 1.3 b 类型?
[Dual Resonant Solid State Tesla coils]
black.yang
January 06, 2019, 08:34:46 AM
post 迎词、来
[General chatting]
black.yang
January 06, 2019, 08:20:21 AM
post Re: Help for people buying the "12-48 Volt 1800/2500 Watt ZVS induction Heater"
[Electronic circuits]
flyrod
January 06, 2019, 12:34:15 AM
post Re: Help for people buying the "12-48 Volt 1800/2500 Watt ZVS induction Heater"
[Electronic circuits]
petespaco
January 05, 2019, 05:27:23 PM
post Re: Help for people buying the "12-48 Volt 1800/2500 Watt ZVS induction Heater"
[Electronic circuits]
flyrod
January 05, 2019, 03:46:29 PM
post Re: (DR)SSTC II
[Dual Resonant Solid State Tesla coils]
Laci
January 05, 2019, 09:51:10 AM
post Re: (DR)SSTC II
[Dual Resonant Solid State Tesla coils]
Mads Barnkob
January 04, 2019, 11:02:25 PM
post Re: (DR)SSTC II
[Dual Resonant Solid State Tesla coils]
Laci
January 03, 2019, 08:38:15 PM
post Re: SimpleDriver v2.3, my phase-shifting QCW DRSSTC controller
[Dual Resonant Solid State Tesla coils]
flyglas
January 03, 2019, 08:15:48 PM