Author Topic: First middle sized DRSSTC - Any suggestions?  (Read 4034 times)

Offline Rapy2

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First middle sized DRSSTC - Any suggestions?
« on: May 02, 2021, 01:23:11 PM »
Hi,
in a month I want to start building my first middle sized DRSSTC. I want to describe my plan here. I will use UD2.7C, I have already built it and tested it.

I am attaching screen of JAVA TC. Is there anything that should be different? I will make the primary coil about 8 turns so I can fine tune it later.

My main question is about bridge construction. I am attaching photo of my layout for the bridge - it´s davekni´s design. I hope it should be fine, maybe I will add some solder to it to make it thicker. Hopefully it will be just fine. I want to use that tranzistors - HGTG30N60A4D. They are tested by this guy up to 430 A peak in bridge configuration - https://www.vn-experimenty.eu/teslov-transformator/drsstc/drsstc-3.html (hopefully the google translation will be good enough, otherwise I will try to describe it, I am from Czech Republic and he is from Slovakia). Firstly I want to build bridge configuration and to try it to let´s say max 370 A peak. But then I want to build double bridge with 8 transistors in total. I don´t expect double the current, but it´s possible that double bridge could handle 700A as example? Unfortunately I can´t afford buying IGBT bricks.

The next thing I'm not sure about is cooling. I am attaching photo of my heatsink, dimensison are written on it. I have two of them. Each heatsink will have 2 or maybe later 4 transistors. I am not sure if it is good enough even if I add cooling fan to them. I'm afraid the transistors will overheat.

The last question is about GDT. I want to use both outputs of my UD2.7C, so 2 GDTs. For single bridge it´s clear. I will use 2 GDTs each with 2 secondary coils. But I wonder if I could use the same GDTs for double bridge (use every secondary coil for 2 transistors in parallel) or I would have to rewind them so each transistor has its own secondary coil, so 2 GDTs each with 4 secondary coils.

Thank you very much for any advice or suggestion  :)

Offline Mads Barnkob

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Re: First middle sized DRSSTC - Any suggestions?
« Reply #1 on: May 02, 2021, 07:48:15 PM »
Hi,
in a month I want to start building my first middle sized DRSSTC. I want to describe my plan here. I will use UD2.7C, I have already built it and tested it.

I am attaching screen of JAVA TC. Is there anything that should be different? I will make the primary coil about 8 turns so I can fine tune it later.

Your coil dimensions look good, that will work just fine. Put in 300 cm in each of the ground, wall, ceiling distance parameters to get some calculations that does not have near objects affecting your secondary coil resonant frequency.

My main question is about bridge construction. I am attaching photo of my layout for the bridge - it´s davekni´s design. I hope it should be fine, maybe I will add some solder to it to make it thicker. Hopefully it will be just fine. I want to use that tranzistors - HGTG30N60A4D. They are tested by this guy up to 430 A peak in bridge configuration - https://www.vn-experimenty.eu/teslov-transformator/drsstc/drsstc-3.html (hopefully the google translation will be good enough, otherwise I will try to describe it, I am from Czech Republic and he is from Slovakia). Firstly I want to build bridge configuration and to try it to let´s say max 370 A peak. But then I want to build double bridge with 8 transistors in total. I don´t expect double the current, but it´s possible that double bridge could handle 700A as example? Unfortunately I can´t afford buying IGBT bricks.

Parallel IGBTs (or any other like diode, transistor, mosfet etc.) will not give you a double rating. It will at BEST give you 50% more if you use matched IGBTs, matched gate resistors and ensure even heat sharing/dissipation. This is most likely a dream scenario and you can just put them on the same heat sink, find the same value gate resistors and only expect 15-20% more current handling.

The next thing I'm not sure about is cooling. I am attaching photo of my heatsink, dimensison are written on it. I have two of them. Each heatsink will have 2 or maybe later 4 transistors. I am not sure if it is good enough even if I add cooling fan to them. I'm afraid the transistors will overheat.

The base is pretty thin, so less thermal mass to take on the high peaks of heat dissipation. Large and largely spaced fins does not add up overall. Forced air cooling is MANY times better than passive. Your sparks are going to make noise anyway, so add a fan with a good air flow!

The last question is about GDT. I want to use both outputs of my UD2.7C, so 2 GDTs. For single bridge it´s clear. I will use 2 GDTs each with 2 secondary coils. But I wonder if I could use the same GDTs for double bridge (use every secondary coil for 2 transistors in parallel) or I would have to rewind them so each transistor has its own secondary coil, so 2 GDTs each with 4 secondary coils.

Thank you very much for any advice or suggestion  :)

Just use one secondary winding for two parallel IGBTs, but give them each their individual gate resistor!

You might want to calculate if you have enough drive current for the double up on gate charge... https://kaizerpowerelectronics.dk/calculators/igbt-gate-drive-calculator/
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 Rapy2

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Re: First middle sized DRSSTC - Any suggestions?
« Reply #2 on: May 02, 2021, 11:55:57 PM »
Thanks Mads  :)
I will use 300cm radius for my calculations.

Thanks for explaining the parallel connection of IGBTs. I absolutely didn´t expect double the current, but I thought that 50% more is possible, but now I know it is not.

I plan to use cooling fan anyway. I will try it with cooling fan and maybe later buy better heatsinks. There is the problem that I have no idea about power dissipation in DRSSTC use. Is there some calculator or equations?

I am glad that I can use same GDTs for bridge or double bridge. I will use single gate resistor for each IGBT.

Offline davekni

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Re: First middle sized DRSSTC - Any suggestions?
« Reply #3 on: May 03, 2021, 04:16:35 AM »
Looks like Mads answered your questions well.  I'll still offer some thoughts too.

Thin heat sinks with sparse fins like what you have were likely meant for natural-convection cooling and lower power.  As Mads said, fans blowing against the back side of the heat sinks will help greatly.  If you can find these in a suitable temperature range at a reasonable price, liquid-crystal strip thermometers taped to the heat sinks would allow monitoring while running.  Most cheap ones are for aquariums etc, with max temperature indication at 40C, a bit low for heat sinks.  Here is an example:
https://www.ebay.com/itm/164791257254
And here is a higher temperature version, but more expensive.  If you can find cheap ones, this would be great:
https://www.amazon.com/Digi-Sense-AO-09035-51-Reversible-Horizontal-Temperature/dp/B01FVOQL84/ref=pd_lpo_328_t_0/134-2808974-2201641
Heat sink limitations can be handled by running lower duty cycles.  Slowly increase duty cycle until IGBTs get hot.

Properly-adjusted phase lead (H-Bridge outputs switching slightly before current zero-crossings) will lower IGBT power dissipation, so allow higher duty cycles before IGBTs get too hot.

Those HGTG30N60A4D IGBTs look interesting.  Data sheet talks about IGBTs as if they were new unfamiliar devices as would be expected for old parts.  But these are quite fast, and do appear to have great peak-current capability.  My guess is that the internal diode will fry before the IGBT as current is increased - especially if hitting OCD frequently so drive is stopping at max current.  That is when diodes conduct, during the ring-down after enable pulses end.  I expect the IGBT itself will work to 430A peak.  If the diode fries, however, the part is still bad, as the diode is likely to fail shorted.  (I ran destructive testing on one of my TO247 IGBTS with a ring-down waveform.  The diode fried first, with the IGBT starting the ring-down at 650A and the diode conducting 600A on the next half-cycle.  Both spec'ed at 240A peak.)

I'm generally more optimistic than Mads on paralleling.  My DRSSTC uses 40 TO247 IGBTs, 10 paralleled for each switch.  Max current is set to 2600A, with 3500A planned eventually.  Another difference:  I parallel IGBTs directly, not using separate gate resistors.  That requires very careful matching of interconnect impedance (same lead length on each device, gate drive feeding from the center, etc.  So, separate gate resistors might be a good idea, but must be well matched.

However, the HGTG30N60A4D IGBT has a negative Vce temperature coefficient at least below 100A.  Current vs. Vge has a positive temperature coefficient even up to the max 350A in the graph.  This makes paralleling less effective.  The warmer device will conduct more current and thus get even hotter.  The result is this:  At low duty cycle where IGBTs are staying reasonably cool, current sharing will be better.  700A per pair might be possible.  600A would be safer.  At higher duty cycle, sharing will be poor, so perhaps 500A for a pair.

One final thought:  If your goal is long arcs, a larger top-load outside diameter would likely help.  If your goal is playing music, your existing top-load is likely best.

Good luck with your build!
« Last Edit: May 03, 2021, 04:23:44 AM by davekni »
David Knierim

Offline Rapy2

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Re: First middle sized DRSSTC - Any suggestions?
« Reply #4 on: May 03, 2021, 01:19:51 PM »
Hi davekni, thanks for your answer  :)
I will probably buy larger heatsinks, hopefully it will he cheaper than in my country. I will use cooling fan too, but larger heatsinks will be 100% better. I want to have my transistors as cold as possible to not risk any overheat or explosion.
About setting the right phase lead, I have some tuneable inductor from old TV, which has the same pinout as 7m3 inductors. I will maybe try to rewind it for the right inductance or just buy some from coilcraft. Sadly shipping to my country cost 3 times more than inductor.

Yeah, I think this IGBT look great for its price. For single bridge I will not go over 350 A peak. But I will probably build double bridge for better results. Hopefully it would be able to take lets say 600A and run fine without overheating. I will definitely use seperate resistor for each igbt.
Your bridge is really interesting. How do you drive so much igbts?
And about heat sharing. As I said, I will buy better heatsinks with powerful fan and try to have all IGBTs as cold as possible for good current sharing.
My goal is long arcs, so I will probably build larger topload.

Many thanks, I really appreciate your advices  :)

Offline Rapy2

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Re: First middle sized DRSSTC - Any suggestions?
« Reply #5 on: May 03, 2021, 04:02:39 PM »
Can you please send some photos of your TO247 bridge? I would be very interested in what it looks like. Thanks  :)

Offline davekni

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Re: First middle sized DRSSTC - Any suggestions?
« Reply #6 on: May 03, 2021, 07:29:14 PM »
I built my DRSSTC (with 40 TO247 IGBTs) just before finding this forum, so don't have any good construction photos.  Here is a link to my after-the-fact documentation:
https://highvoltageforum.net/index.php?topic=798.msg5285#msg5285
Each set of 10 IGBTs has it's own final gate-drive stage (NFET/PFET pair) on floating 18V supply.  Isolation is with Si8274 driver chips instead of GDTs.  The initial runs there were with only 3kW bulk supply, which I've since increased to 6kW, then to 8kW.  Later images show 10' (3m) arcs using ramped pulse width.

If I'd found the forum first, would have used bricks instead of doing all the work to parallel TO247 devices.  I hadn't thought bricks could run at 80kHz.  Learned here that they can, at least the faster ones.
David Knierim

Offline Rapy2

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Re: First middle sized DRSSTC - Any suggestions?
« Reply #7 on: May 04, 2021, 12:34:29 AM »
Looks very interesting :) Thanks for the link.

I thought about using some IGBT brick, but there are some problems. I think that about 150 khz is way to high for brick and its too expensive. And I don't trust ebay sellers enough to buy used. When I was looking for a suitable IGBT brick, I found that the ones I could afford have much worse parameters than the TO247s, just maximum power dissipation was larger. I think that its also not the right way to buy some large IGBT brick like CM300 and think it is indestructible. It will be my first DRSSTC, so TO247 double bridge will be hopefully just fine for first DRSSTC.

Offline Rapy2

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Re: First middle sized DRSSTC - Any suggestions?
« Reply #8 on: May 04, 2021, 12:57:12 AM »
I just looked at the datasheet of your TO247 IGBTs. I am quite a beginner, so it is not easy to compare them with my choice. Do you think it is better to use HGTG30N60A4D or STGW60H65DRF for my application?
I noticed that STGW60H65DRF has more than double the thermal resistance junction-case diode and it also has higher on, off times.

Thank you very much for your help.
« Last Edit: May 04, 2021, 01:06:26 AM by Rapy2 »

Offline davekni

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Re: First middle sized DRSSTC - Any suggestions?
« Reply #9 on: May 04, 2021, 01:50:12 AM »
The IGBTdie of HGTG30N60A4D is clearly better (excepting the temperature coefficients making paralleling harder).  Yes, STGW60H65DRF diode thermal resistance is higher than its IGBT thermal resistance.  That is what keeps me from using pulse-skipping.  STGW60H65DRF diode temperature coefficient is also the wrong direction for paralleling (like HGTG30N60A4D), but the IGBT coefficient is good for paralleling.

Unless you have a more complete data sheet than I found, my biggest concern with HGTG30N60A4D is that I see no information on diode thermal resistance, and the diode forward voltage drop data ends at 35A.  STGW60H65DRF specifies 240A diode current capability for 1ms, and has graphs going out to high current.

HGTG30N60A4D doesn't show up as available very many places.  I hadn't found that part in searching, so didn't consider it.  STGW60H65DRF diode capability questions is a key reason I ran tests on a couple parts, running them to destruction.  I'm still not sure if the diode's temperature coefficient and associated paralleling issues will cause a failure when I eventually increase current above 2600A.  Individual parts can easily handle 350A, but I haven't figured out any way to measure current sharing accurately.
David Knierim

Offline Rapy2

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Re: First middle sized DRSSTC - Any suggestions?
« Reply #10 on: May 04, 2021, 11:19:14 AM »
Well, it looks like the HGTG30N60A4D are quite old.  I also did not find any further information about forward diode voltage drop with current higher than 35A.  They are still easily available in my country, so I will probably buy them and I will trust the person who tested them up to 430A peak (I shared a link to his site).  He tested them up to 430A peak and even after a few minutes his heatsinks were almost cold.  For my double bridge, I will try to keep them as cold as possible.

Offline Rapy2

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Re: First middle sized DRSSTC - Any suggestions?
« Reply #11 on: May 05, 2021, 11:17:11 AM »
I would like to ask the last question. If I ever decide to build a bigger coil with a lower frequency and use IGBT bricks, is it possible to get good IGBT bricks from ebay? Do you have any experience with that, please? I know they are used, but I don't mind at all, new ones are too expensive.

Offline TMaxElectronics

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Re: First middle sized DRSSTC - Any suggestions?
« Reply #12 on: May 05, 2021, 12:21:48 PM »
Used bricks are usually no problem as they are pretty rugged. I got some used SKM400 bricks from Netzpfuscher for my big coil and they haven't caused any problems so far.

But consider if you have the space for a large coil before you build it ;)

A 1m coil might just work in a basement if there is plenty of room around it, but anything larger needs an open field or at least something like a barn (that also has enough electricity to supply the coil). And it's probably obvious, but since the tesla coils are of course obscenely loud your neighbours might not like it if you ran it in your garden.

I built my 2m coil expecting to run it at the HV lab of a nearby university, but that isn't possible at the moment due to covid rules, and since I have neighbours I can't run it in the garden (except for new years eve :P).
Because of that it has been standing in the basement collecting dust.

Offline Rapy2

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Re: First middle sized DRSSTC - Any suggestions?
« Reply #13 on: May 05, 2021, 01:03:30 PM »
Thanks Max for your answer :)

Now after secondary school I want to build middle sized DRSSTC, with base and topload about 1m.

Maybe later in the future, I will build larger coil with lower resonant frequency and with IGBT bricks.

I am sorry for your coil  :-[ I have the advantage of having a second house in a small village on the outskirts. There are only fields and forests. It is a small farm, so I have no problem here and I can build a larger coil.

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Re: First middle sized DRSSTC - Any suggestions?
« Reply #13 on: May 05, 2021, 01:03:30 PM »

 


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[Transformer (Ferrite Core)]
Mads Barnkob
March 20, 2024, 08:03:41 PM
post Re: 2x Panasonic Inverter Microwaves - what to salvage, dangers?
[General Chat]
Mads Barnkob
March 20, 2024, 07:51:57 PM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
March 20, 2024, 10:39:47 AM
post Re: Phase Lead Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
March 20, 2024, 04:09:59 AM
post Re: 160mm DRSSTC II project | Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Benjamin Lockhart
March 20, 2024, 01:13:23 AM
post Re: Phase Lead Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Keybored
March 20, 2024, 12:45:16 AM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
March 20, 2024, 12:30:30 AM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Benjamin Lockhart
March 19, 2024, 11:12:24 PM
post Re: 160mm DRSSTC II project | Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Late
March 19, 2024, 09:47:49 PM
post Re: 160mm DRSSTC II project | Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Late
March 19, 2024, 09:44:19 PM
post Phase Lead Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Saattvik24
March 19, 2024, 06:52:09 PM
post Re: 160mm DRSSTC II project | Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
March 19, 2024, 05:02:44 PM
post Re: Welcome new members, come say hello and tell a little about yourself :)
[General Chat]
Mads Barnkob
March 19, 2024, 05:01:41 PM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
March 19, 2024, 04:31:02 PM
post Re: 160mm DRSSTC II project | Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
March 19, 2024, 03:59:54 PM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Benjamin Lockhart
March 19, 2024, 06:41:39 AM
post Re: Welcome new members, come say hello and tell a little about yourself :)
[General Chat]
davekni
March 19, 2024, 04:05:49 AM
post Re: Welcome new members, come say hello and tell a little about yourself :)
[General Chat]
OmGigaTron
March 18, 2024, 09:08:35 PM
post Re: Can I Trust This Super Cheap Site?
[General Chat]
2020-Man
March 18, 2024, 09:07:35 PM
post Re: Can I Trust This Super Cheap Site?
[General Chat]
Twospoons
March 18, 2024, 08:57:06 PM
post Re: Can I Trust This Super Cheap Site?
[General Chat]
MRMILSTAR
March 18, 2024, 03:51:33 PM
post Re: 160mm DRSSTC II project | Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Late
March 18, 2024, 02:59:46 PM
post Re: 160mm DRSSTC II project | Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Late
March 18, 2024, 02:33:25 PM
post Can I Trust This Super Cheap Site?
[General Chat]
2020-Man
March 18, 2024, 11:02:12 AM
post Re: Where's all this voltage coming from?
[Spark Gap Tesla Coils (SGTC)]
Twospoons
March 18, 2024, 02:36:11 AM
post Re: Best forum for vacuum tube amplifiers?
[General Chat]
Mads Barnkob
March 17, 2024, 07:42:55 PM
post Re: 2x Panasonic Inverter Microwaves - what to salvage, dangers?
[General Chat]
Michelle_
March 17, 2024, 04:15:14 PM
post Re: 2x Panasonic Inverter Microwaves - what to salvage, dangers?
[General Chat]
Michelle_
March 17, 2024, 05:05:04 AM
post Re: Where's all this voltage coming from?
[Spark Gap Tesla Coils (SGTC)]
davekni
March 17, 2024, 04:50:51 AM
post Re: 2x Panasonic Inverter Microwaves - what to salvage, dangers?
[General Chat]
Twospoons
March 17, 2024, 04:45:17 AM
post 2x Panasonic Inverter Microwaves - what to salvage, dangers?
[General Chat]
Michelle_
March 17, 2024, 04:17:51 AM
post Where's all this voltage coming from?
[Spark Gap Tesla Coils (SGTC)]
Terry
March 17, 2024, 01:29:32 AM
post Re: DRSSTC Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
March 17, 2024, 12:33:06 AM
post Re: DRSSTC Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Keybored
March 16, 2024, 08:46:20 PM
post Re: Bleeder resistor for MMC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Hydron
March 16, 2024, 08:39:24 PM
post Re: DRSSTC Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Hydron
March 16, 2024, 08:21:44 PM
post Best forum for vacuum tube amplifiers?
[General Chat]
yourboi
March 16, 2024, 08:20:13 PM

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