A few questions

[ako]

Hi Voltage folks,

I am quite new here and reading now for a few weeks. I already have built and played around with an SGTC with a ZVS powered flyback transformer and diy rolled caps.
The first music I've heared came out of the same flyback transformer driven with an Arduino/NE555 controlled IRFP460.

My next goal now is to build (actually... have) a DRSSTC.

I say 'actually have' because I would have bought me a OneTeslaTS kit and built it in the hope having the feeling of 'building' a DRSSTC on my own and much more important in the hope of learning how everything works while expecting that it'll work when finished.

This brings me to my first question:

Is the OneTesla team still active somehow? Their products are out of stock since I am watching their site now for weeks and I also have contacted them via their contact form but I haven't received any reply at all.

Can I get a similar kit somewhere in Europe (I am living in Germany)?

Another question is:

Which PCB of those you awesome guys have created and thankfully provided here in this forum for us to download would be compareable to the one of the OneTesla kit?

As I would like to end up with a (you guys would say) small compact looking coil, which I can leave standing on a shelf without having my wife complaining about it. That's why I would like to have the primary on a PCB too (which in my opinion makes the whole construct look more neat).

Are there already some combinations with driver and primary PCBs available for download here already which I might have missed?

My next question:

I have already some parts salvaged (out of some big CNC machine motor drivers I guess) at hand. Can you guys have a look at them (I'll attach the pics when I'm done writing and don't know where they show up here) and tell me if I can make use of them? I am sure though, that - if - those parts will be nothing for my first compact build. But anyways, if I sometime succeed and build my first, I am pretty sure that it will be not my last... but my smallest.



I hope I did nothing wrong and didn't void any board rules and also didn't bother you with my questions.

I appreciate any help and advice and all of your work and information you guys have put into this forum so far.

[davekni]

Can I get a similar kit somewhere in Europe (I am living in Germany)?

The only other TC kit company I am aware of is Eastern Voltage Research (EVR for short).  My limited experience with them is mediocre at best.  I have helped a couple people get their EVR coils working.  I'd be happy to help remotely with debug of whatever you decide to build in the end.  This forum is a good place for such.

Hopefully you'll get other answers if there are any small integrated designs as you are searching for.

Good luck with your project!

[ako]

You see... with all googling and looking for kits and stuff this EVR site didn't come up though. I see it for the first time now. Thanks for the hint. They seem to have really a lot to offer. Unfortunately, besides their not really that cheap prices for their coil kits, they seem to be located in US too. So if I ordered a kit there, including tax fees and shipping costs, I really would pay disproportionately much for something I could get a lot cheaper with putting some brainjuice into it.

I am just doing my first serious steps with KiCad and EasyEDA in parallel and try to rebuild the OneTeslaTS board with the help of the schematics and the pictures they provide for download on their site. I know this might sound like am trying to be some sort of copycat and stuff, but I contacted them asking for all possible options for me to get their product, either by buying the kit or maybe by them providing PCB files (even with being ready to pay for that) so that I can order those at some PCB manufacturer. But like I said, unfortunately no reaction from them at all.

The schematics of their driver is pretty simple and I would easily be able to build it all manually on a perfboard, but I would like to use this opportunity and end up having some sort a semi-professional product when I'm done and not another completely DIY looking gadget flying around and collecting dust.

But if I really should be able to get  a compact driver built, the biggest hurdle still will remain the design of a PCB primary, as I am not that experienced or educated in the physics and formulas involved. I would need a significant amount of time (and most likely money) to get behind that. So if anyone here could give me some hints or links to maybe some sites with calculators like the JavaTC that would make my life easier, I would really appreciate that.

I already have most of the BOM of the OneTeslaTS in my bucket on ebay, including the gate drivers, the IGBTs, the 74HC*** ICs. All resistors and diodes and other small stuff I am pretty sure I have somewhere in my small parts boxes or still mounted on one of the bunch of boards from all kind of salvaged electronics that I have in my workshop. What I couldn't find so far is the primary cap with the same values and I am not sure about the current transformer. I have a few of those on some boards (like the one in the picture in my first post) and I would like to know if there is a way to test them to find out if they would suite? Any hints?

[davekni]

The schematics of their driver is pretty simple and I would easily be able to build it all manually on a perfboard, but I would like to use this opportunity and end up having some sort a semi-professional product when I'm done and not another completely DIY looking gadget flying around and collecting dust.

Perfboard builds are more likely to have issues with signal integrity, as most do not have ground planes.  A well-designed ECB will perform more reliably besides looking better.  I see KiCad used here more often than any other ECB tools, so started using it a couple years ago.  Powerful free tools well worth learning.

So if anyone here could give me some hints or links to maybe some sites with calculators like the JavaTC that would make my life easier, I would really appreciate that.

JavaTC should get you close enough.  Primary loss will be higher (Q lower) than JavaTC predicts due to actual thin traces instead of thick wire.  Otherwise it should be close enough.  If you want to learn FEMM, that would be the more precise and involved option.  Make ECB from 2oz copper to minimize loss.
For primary frequency adjustment, either include multiple spaced taps (ie. through-holes) along primary, or provide space for a few smaller caps across primary series capacitor to allow tweaking cap value.

I already have most of the BOM of the OneTeslaTS in my bucket on ebay, including the gate drivers, the IGBTs, the 74HC*** ICs.

Be aware that there are many counterfeit parts being sold, on EBay etc. and on Chinese specific sites too.  IGBTs are most likely to be questionable.  Other parts such as 74HC14 will likely work well enough whether genuine or not.  IGBTs might too.  However, these simple small DRSSTC designs lack lead compensation.  IGBTs are hard-switched (switched while conducting current), so experience higher stress.
BTW, IGBT bricks as shown in your initial post are generally good for larger lower-frequency coils.  Small ones are usually too high frequency for such IGBTs.

What I couldn't find so far is the primary cap with the same values and I am not sure about the current transformer. I have a few of those on some boards (like the one in the picture in my first post) and I would like to know if there is a way to test them to find out if they would suite? Any hints?

Primary cap is unlikely to be found in salvaged equipment, at least that's my experience.  Most DRSSTCs use an array of smaller caps called "MMC" for primary cap.  Sometimes small ones do have a single cap as in the OneTesla example.
I see one brown object at the bottom of your image that seems likely to be a CT.  Good chance it would work for a small coil.  100:1 is most common for such board mount CTs.  What equipment to you have around?  Scope and signal generator?  LRC meter?

[ako]

What equipment to you have around?  Scope and signal generator?  LRC meter?

Check, check and check. A Hantek USB scope I bought a couple of years ago, a Peaktech 3440 and one of those cheap LCR T7 Multi transistor testing tools.

[davekni]

A Hantek USB scope I bought a couple of years ago, a Peaktech 3440 and one of those cheap LCR T7 Multi transistor testing tools.

For measuring possible CT, LCR meter would be easiest, though might be a problem if LCR meter frequency is too low.  10kHz might be OK.  100kHz would be better.  Scope and signal generator will be more reliable.
Either way, I'd wind 10 turns of wire around CT core, through the hole where one wire normally passes.  Check pins for continuity.  Presumably only one pair will connect.  For LRC meter, measure inductance of pin pair and of 10-turn winding.  Turns ratio will be sqrt(inductance ratio).  For scope, connect signal generator to pin pair and run at ~100kHz.  Scope waveform across pin pair and then across 10-turn winding.  Voltage ratio is turns ratio.  Make sure signal generator output has no DC component.  Add a series capacitor to make sure.

CTs aren't difficult to make if you have cores.  Line input common-mode choke cores generally work well.  Other salvage cores are not likely to be good.  Large EMI filter beads can work as CT cores, but will require more testing to verify.  Same core options for GDTs.

[ako]

Another question which came up:

I see different schematics which mostly look similar but some use a combination of UCC37322 and UCC37321 and some use a pair of those two.

I'm sure that I get it right that the difference of those two chips is the inverted output. So a 1 signal on input gives an 0 signal on output with the inverted version and 1 input 1 output with the non-inverted version.

My question now is:

Is the result basically the same when I use a combination of those two chips and connect the output wires of the GDT to the IGBTs (technically to one half of the bridge) 1 to 1 to the IGBTs or when I use a pair of one of those ICs but inverting the signal by connecting the outputs wires of the GDT not 1 to 1 but flip the two wires for on half of the bridge?

[davekni]

Is the result basically the same when I use a combination of those two chips and connect the output wires of the GDT to the IGBTs (technically to one half of the bridge) 1 to 1 to the IGBTs or when I use a pair of one of those ICs but inverting the signal by connecting the outputs wires of the GDT not 1 to 1 but flip the two wires for on half of the bridge?

No.  When using same driver chips, input of one chip is inverted.  Simulation is the easiest way to understand.

[ako]

Alright... next question(s)

GDTs....

Is there a method (in addition to attaching a square wave signal to the input and the oscilloscope to the output winding) to find the right cores to use, when you have a bunch of them in all different sizes and colors, like I do (not only) here:


On the board from my initial post, there is this section, which strongly looks like a gate drive circuitry


The two red(ish) blocks on the left look (and behave) like GDTs. Datasheet is attached, but unfortunately only in german. Directly translated, the datasheet says those are "Ignition Transformers".
I did the signal/oscilloscope test (on ~340kHz the resonant frequency of the secondary + topload) and at a first glance, I would consider this here as a clean square wave output signal

Question is, is there some property (I lack the knowledge of) in the datasheet which would make these GDTs unusable for a DRSSTC?

On the section of the board there are also the two ICs on the right side. Those are TLP2200s and according to the (attached) datasheet they are gate drivers.
Would those be usable?

[Mads Barnkob]

Generally you can not use ferrite cores found in noise filtering, as GDT cores, simply because material could be a wide variety between coarse iron powder and well suited high frequency material, we just dont know. Color cant tell, grain coarse cant tell, shape cant tell. Its just a gamble, unless you pulled it from something you know is a 100 kHz+ circuit.

Industrial GDTs are in general pretty small, so that means its a thin wire and small core. Thus it needs more turns than a homemade 15:15:15 GDT driven at 24V. This means that its peak current capabilities is maybe 10-fold lower than a homemade. And all we want in a Tesla coil, where we overdrive the IGBT gates from normal +/- 15V to 24V, is because we want FAST switching. We want fast switching because we drive much larger currents than the switches are meant to handle, part due to resonance we get away with this, but we still need fast switching to keep the turn on/off losses within the hardswitching specifications of the IGBTs.

[davekni]

Question is, is there some property (I lack the knowledge of) in the datasheet which would make these GDTs unusable for a DRSSTC?

On the section of the board there are also the two ICs on the right side. Those are TLP2200s and according to the (attached) datasheet they are gate drivers.
Would those be usable?

TLP2200s are optical couplers.  Would require buffering of output to drive any significant gate capacitance.  Given the use of isolators, I'd guess the "GDTs" are more likely transformers used to generate isolated DC gate drive supply rails.  Even if they are GDTs, I completely agree with Mads' comments about those.

Is there a method (in addition to attaching a square wave signal to the input and the oscilloscope to the output winding) to find the right cores to use, when you have a bunch of them in all different sizes and colors, like I do (not only) here:

You can narrow down the list of possibilities, but any final use should include testing first.  Any core with a single winding is not suitable.  It is an inductor with an almost-certainly powdered (iron...) core.  The cores with two identical windings on separate halves separated by a space are likely line input common-mode filter chokes.  Those are quite likely to work (presuming they are large enough for your needs).    Other cores with multiple identical windings might be OK.  The largest bare black core in the image might be OK for a reasonably-high-frequency coil, but needs testing.  I have a couple bags of similar cores from a surplus sales outfit.  One is reasonably good, the other not.

[ako]

Alright guys...

the more I read and the more (barely) different schematics I study, the more I tend to say F it designing my own OneTesla clone board. I guess it's a better idea to take what's already been done and tested by people who really know what they're doing and go with one of those (and that's actually my question now) UDs which are available for download.

What is the most current version which I should aim for? For sure those 3.0 and up versions look really interesting, basically with their own operating system to tinker with. Getting the board ordered and (even SMD) soldering are really no big deal for me but what really annoys me is to get all the parts ordered... You mostly don't find all needed parts at one supplier, another parts you don't find at all with a reasonable delivery time... that sux... and beside all that, I most probably have all needed parts anyways somewhere on all those circuit boards which I have in my basement.

Does someone here maybe have a spare UD 3.0 or up to offer for sell? Netzpfuscher or someone else from Germany maybe? I would also take it as some sort of kit, so board and parts for self soldering basically.

[ako]

OK guys,

I guess I need to hear your thoughts now:

I have actually copied and built the OneTeslaTS schematics, wound a GDT after davekni's tutorial (thanks for that), connected a signal generator with a frequency set to the resonant frequency I will expect my secondary coil to have to the CT and connected the oscilloscope probes to the secondary windings and this is what I get now:


That's the current state of my build:


The lines stay flat until I set a frequency on the interrupter which I built with an Arduino Uno with a keypad shield and which I connect to the driver with a Toslink fiber connection.

Does this look OK so far? Can I continue to build the half bridge?

And... Do I read the schematics here at this place right when I say that the low sides of the secondaries of the GDT are connected to the IGBTs in a inverted way, like one low side to the gate of IGBT2 and the other low side of the other secondary to the emitter of IGBT1?

[davekni]

I have actually copied and built the OneTeslaTS schematics, wound a GDT after davekni's tutorial (thanks for that), connected a signal generator with a frequency set to the resonant frequency I will expect my secondary coil to have to the CT and connected the oscilloscope probes to the secondary windings and this is what I get now:

Is the signal generator wired directly to GDT or through driver?  If direct, output looks fine.  If through driver, amplitude is far too low.

The lines stay flat until I set a frequency on the interrupter which I built with an Arduino Uno with a keypad shield and which I connect to the driver with a Toslink fiber connection.

Most drivers are built to output signal only when light is fed through fiber.  Sounds like yours is opposite.  If so, that runs the risk of frying half-bridge if interrupter signal gets weak or disrupted.

Does this look OK so far? Can I continue to build the half bridge?

Picture looks fine.  Protoboard driver is small, reducing issues common with the lack of ground plane.  Still depends on back-side connections, number and location and wiring of bypass capacitors, ideally a grid of ground connections.

And... Do I read the schematics here at this place right when I say that the low sides of the secondaries of the GDT are connected to the IGBTs in a inverted way, like one low side to the gate of IGBT2 and the other low side of the other secondary to the emitter of IGBT1?

Yes.  One IGBT is on while other is off.  Depending on your specific IGBT parts and slew rate of GDT outputs, you likely will need a series resistor with parallel diode between each gate and it's GDT output wire.  That provides dead-time, time for one IGBT to turn off before other IGBT turns on.

[ako]

and another question... let's see if I begin to really understand how stuff is actually working...

In the OneTeslaTS schematic, if I wanted to swap the two UCC37321 with two UCC37322, in order to get it working, would I need to feed the \Q' output of the flip flop which directly goes to both EN inputs of the UCCs through another inverting gate of the HCT14 first?

Edit: ...or would it be sufficient to just connect the EN inputs of the UCCs to the \Q output of the flip flop instead of the \Q' (pin 5 instead of pin 6)?

[davekni]

In the OneTeslaTS schematic, if I wanted to swap the two UCC37321 with two UCC37322, in order to get it working, would I need to feed the \Q' output of the flip flop which directly goes to both EN inputs of the UCCs through another inverting gate of the HCT14 first?

No, EN pins are same polarity in both chips.  Only needed change is to swap direction of CT feedback wires to invert feedback polarity.

[ako]

Alrighty... things are evolving...

Reached first light, many - many - bangs and booms, coil rewindings, IC / IGBT orders and replacements on the road so far... I fell in love with ordering stuff from Digikey... shipment from US to Germany in 2 days. No shipping costs when order exceeds 50€... I was about to order 6 capacitors... would have cost me something around 53€ including shipping and taxes, thank god I had the idea to order 12 instead... no shipping costs, including taxes 59€

And now.... I am absolutely amazed... these just came in, ordered on Monday at JLCPCB.


Some of the bridge PCBs, the UD 2.9 and the Psoc5 from the DRSSTC PCB pack... Let's see how that will be going, going to start with the 2.9 Questions most likely to come up! Any already available and/or suggestions and tips are absolutely welcome.

[ako]

OK... first question... more a general one regarding capacitors and their values:

Can I use caps with the correct capacitance but with higher voltage rating than what is given in the BOM? Like if BOM says 1nF 50V ceramic but I use 1nF 2KV?

[davekni]

Can I use caps with the correct capacitance but with higher voltage rating than what is given in the BOM? Like if BOM says 1nF 50V ceramic but I use 1nF 2KV?

Higher voltage rating is fine.  Dielectric material is often more important.  Z5U and Y5V caps are almost worthless.  NP0 (same as C0G) is best, but not available for large-value caps.  X7R (and if necessary X5R) is appropriate for larger value capacitors.  There is still a wide range of performance within X7R, especially how much capacitance drops as DC voltage increases, sometimes down to -90% (only 10% of capacitance left) at rated voltage.

[ako]

Cool...

I am just assembling the UD 2.9 and I have almost all parts I need to finish it... except for three resistors - R13/R25 1.8K Ohm, R11 5.1Ohm and R3 51Ohm. Do I need to be precise with those resistors and their values or can I vary a little bit like e.g. using 2 10 Ohm or 2 100 Ohm in parallel or one 1K Ohm and one 750 Ohm in series?

And for the 51 Ohm the BOM says metal film... does it have to be metal film (if yes, why) or can I use carbon film resistors too? Just asking because I could still order carbon film type at Amazon and get them delivered tomorrow.

And... would you recommend using DIP sockets for the the ICs on the UD2.9 or is the driver robust at all, so that I don't need to expect the ICs like the 74s getting fried for whatever reason... I don't know how to be honest, but while dealing with the OneTesla type of driver I somehow managed to send those HCT74s and HC14s to hell on a daily basis

[davekni]

I am just assembling the UD 2.9 and I have almost all parts I need to finish it... except for three resistors - R13/R25 1.8K Ohm, R11 5.1Ohm and R3 51Ohm. Do I need to be precise with those resistors and their values or can I vary a little bit like e.g. using 2 10 Ohm or 2 100 Ohm in parallel or one 1K Ohm and one 750 Ohm in series?

And for the 51 Ohm the BOM says metal film... does it have to be metal film (if yes, why) or can I use carbon film resistors too? Just asking because I could still order carbon film type at Amazon and get them delivered tomorrow.

Presuming I'm looking at the same UD2.9 schematic:
R13 sets maximum OCD threshold (top voltage of 10k POT RV1).  Range looks too high on UD2.9 in my opinion, since dividing from 12V rather than 5V or 9V as in other driver designs.  So I'd use a larger value for R13, 5k or 10k.
R25 is a pull-up resistor, so not critical.  2k or even 3k would work.
R11 (and R12 which you didn't mention) are OCD CT burden resistors.  Calculate what current your CT will generate at your intended OCD limit.  Then pick a resistance that gives a reasonable voltage (say 5V) at that current, for the parallel combination of R11 and R12.  Doesn't need to be close to 5.1 ohms, but does need calculating.
R3 is the feedback CT burden resistor.  It needs to handle high peak power, so must be a resistor type appropriate for high peak power.  How high depends on your primary current and feedback CT ratio.

Sounds like you are in a hurry.  That can lead to problems.  Relax and think things through.  (BTW, I'll not be around to answer for a few days.)

And... would you recommend using DIP sockets for the the ICs on the UD2.9 or is the driver robust at all, so that I don't need to expect the ICs like the 74s getting fried for whatever reason... I don't know how to be honest, but while dealing with the OneTesla type of driver I somehow managed to send those HCT74s and HC14s to hell on a daily basis

No clear answer that I know.  Sockets add inductance to IC pins, especially power pins, so can cause problems.  Adds thermal resistance too, important only for the UCC driver chips.  I'd not socket UCC driver chips, even though those are more likely to be ones to fry.  Depending on the socket and chips, sometimes bad socket connections can also cause hard-to-diagnose problems.

Hope your build goes well!

[ako]

Dude... First of all - You are awesome!

Thanks for having a look at the schematics and for the very detailed explanation regarding the resistors. That already helped me a lot and gave me a direction to head to and do more closer reading and understanding.

I am not in a hurry... it's just the little kid in me who gets excited. As long as the other old working and money earning guy in me can afford that little boys excitement, it's all fine. That's also how I got where I am with my skills today... Since my early childhood I always broke stuff first before I actually learned how it's working while trying to repair it again.

What you say about the IC sockets sounds damn right and I'll leave them out on this build (I still have 4 more spare PCBs to learn from and do it better in case it's the wrong decision). During the first build I really had that feeling that every now and then something fried just because I had touched some pins of the ICs with the oscilloscope probe.

I guess the next task for me to do now is to get how to measure the primary current and do some math. Measuring the currents is something I lacked the motivation for till now. I know that's something essential to do and I guess I reached the point of no return. Have to go that way now.

[davekni]

During the first build I really had that feeling that every now and then something fried just because I had touched some pins of the ICs with the oscilloscope probe.

Yes, slipping with a scope probe tip is an easy way to fry parts, primarily parts with more power than just logic ICs, such as gate drivers.  I fried a gate driver that way on my DRSSTC during initial check-out.

I guess the next task for me to do now is to get how to measure the primary current and do some math.

Measuring will be helpful later for debug.  Initially it is more important to decide how much current your IGBTs are capable of.  I think Mads has a guide for typical IGBTs used here.  My rule-of-thumb for TO247 packaged parts is that they fry at 2x rated peak current or 4x rated continuous current, given the soft-switching of DRSSTC use.  OCD limit is intended to prevent IGBT failure, so usually set based on IGBT capability rather than by measured current.

[ako]

Alright then...

Just received another batch of 10 FGA60N65SMD IGBTs a few minutes ago... I think 300A seems to be a good value to work with like this guy here http://www.personal.psu.edu/ahy5028/DRSSTC1.htm I found via Mads' design guide. I have almost exactly the same values. I didn't bother to convert his imperial and AWG wire values to metric but the resonant frequencies are in the same range. I measured 272kHz for my secondary with topload and a wire as streamer simulator and I've wound a flat primary which I measured 243kHz for at that clamp point you can see here... (UD 2.9 also almost finished, LM311 is missing which I should get tomorrow)



So... 300A...

Calculate what current your CT will generate at your intended OCD limit.  Then pick a resistance that gives a reasonable voltage (say 5V) at that current, for the parallel combination of R11 and R12.  Doesn't need to be close to 5.1 ohms, but does need calculating.

If I have a 1:1000 CT (1:33:1:33), do I get ~0.3A and need 16.66Ohm resistance to get a 5.0V signal? Is that math correct? I have to check how much voltage the input of LM311 tolerates right, to know the maximum R value I can use?

[davekni]

If I have a 1:1000 CT (1:33:1:33), do I get ~0.3A and need 16.66Ohm resistance to get a 5.0V signal? Is that math correct? I have to check how much voltage the input of LM311 tolerates right, to know the maximum R value I can use?

BTW, 33 * 33 = 1089:1 CT ratio.  Close enough.
Yes, any resistor in the 10 to 20 ohm range would be fine.  Default UD2.* values tend to be for large coils using IGBT bricks for H-bridge.

Presuming same ratio for feedback CT, ~0.3A across 51 ohm is plenty low, so likely any 1W or 2W resistor is likely fine.

[Boilerbots]

You could have purchased most parts you need to assemble a fully working DRSSTC through ebay or Aliexpress if you just want to get something running and play around with it. This is what I was thinking when you first started asking about the oneTesla kits. There are quite a few kits of fully working TCs on there.

[ako]

BTW, 33 * 33 = 1089:1 CT ratio.  Close enough.
Yes, any resistor in the 10 to 20 ohm range would be fine.  Default UD2.* values tend to be for large coils using IGBT bricks for H-bridge.

Cool, seems I am on the right path then... In order to make use of 5W 15Ohm resistors (being in that resistance range and as I have a few of those) I rewound the CTs with a ratio of 1:625... which should be 0,48A if I remember well. So using another 15 Ohm as burden resistor for feedback should also be fine I guess, right? At least feedback seems to work very well per my tests with a signal generator running at my primary resonance frequency and scoping the gate signals.

 [ You are not allowed to view attachments ]

I still have to add the burden resistor and then I can start to do some initial tests. Will be a good opportunity to do first screenshots from my scope I recently bought... which brings me to:

You could have purchased most parts you need to assemble a fully working DRSSTC through ebay or Aliexpress if you just want to get something running and play around with it. This is what I was thinking when you first started asking about the oneTesla kits. There are quite a few kits of fully working TCs on there.

I know I could have done that... but I didn't... and passed the point of no return months ago.

[davekni]

So using another 15 Ohm as burden resistor for feedback should also be fine I guess, right?

Might be fine.  Issue with low feedback burden resistor value is startup.  At beginning of each enable pulse, first half-cycle of output needs to generate enough feedback signal to generate the next half-cycle.  Especially for any testing at low H-bridge bus voltage, feedback amplitude of first half-cycle might be insufficient.  Feedback amplitude will be plenty high across 15 ohms once primary current builds up for a few cycles.
One way to fix startup issues is with self-oscillating mod's I've posted for UD2.7 (same feedback input circuit as UD2.9).  However, for your first coil, custom modifications add too much complexity.

Will be a good opportunity to do first screenshots from my scope I recently bought.

Great to hear that you have a scope.  That is a critical tool to get coils running.

I noticed screw terminals for your IGBT leads.  Makes changing parts easy, but also increases chances you will need to change parts.  Added lead inductance causes problems.  Primary issue is emitter lead inductance.  High emitter current causes voltage drop along lead.  That voltage gets subtracted from gate signal, distorting Vge.  Bridge ECB layout can add even more parasitic inductance.  I can't tell from the one image how your ECB looks.  BTW, just for reference, here's my tutorial on low-parasitic-inductance half-bridge construction:
https://highvoltageforum.net/index.php?topic=1324.msg9795#msg9795

[ako]

Might be fine.  Issue with low feedback burden resistor value is startup.  At beginning of each enable pulse, first half-cycle of output needs to generate enough feedback signal to generate the next half-cycle.  Especially for any testing at low H-bridge bus voltage, feedback amplitude of first half-cycle might be insufficient.  Feedback amplitude will be plenty high across 15 ohms once primary current builds up for a few cycles.
One way to fix startup issues is with self-oscillating mod's I've posted for UD2.7 (same feedback input circuit as UD2.9).  However, for your first coil, custom modifications add too much complexity.

I guess I am just experiencing exactly that... since the last picture I added the 15Ohm burden and a heatsink to those voltage regulators as those get pretty hot, barely to touch. Now hooked up everything again with the signal generator through the CT but don'T get anything on the gates.
Checked the 3 voltages rails and those are fine... 5, 12 and 24 Volts where they belong to. How do I calculate the burden resistance I'll at least / at maximum need? How are the rules there? What voltage/current do I need to achieve at which point?

And I am also not sure about all of those jumpers I can place to enable/disable/set some stuff... Most of them I do get... But a few are missing descriptions on the schematics and don't know yet if placing a jumper enables or disables stuff.

[davekni]

I guess I am just experiencing exactly that... since the last picture I added the 15Ohm burden and a heatsink to those voltage regulators as those get pretty hot, barely to touch. Now hooked up everything again with the signal generator through the CT but don'T get anything on the gates.

Probably similar, but in this test case, issue would be 15 ohms loading signal generator output down to too low a voltage.  Measure voltage across UD2.9 CT input.  Voltage required to start is around 0.2V depending on forward drop of D5.

How do I calculate the burden resistance I'll at least / at maximum need? How are the rules there? What voltage/current do I need to achieve at which point?

Haven't seen any calculation guides for startup.  So here's a quick procedure:  Calculate primary impedance at resonant frequency.  First half-cycle current is half-bridge output voltage (half of Vbus) divided by primary impedance.  Voltage is burden resistance times current divided by CT ratio.  UD2.x requires about 0.2V to start.  To be more precise, measure voltage across D5 when quiescent.  Startup requires slightly more than D5 quiescent voltage.

And I am also not sure about all of those jumpers I can place to enable/disable/set some stuff... Most of them I do get... But a few are missing descriptions on the schematics and don't know yet if placing a jumper enables or disables stuff.

Many of the "jumpers" are scope test points, not intended for any jumpers to be installed.  Critical one is J4.  If L1 is not installed (no phase lead), then J4 must be shorted.

[ako]

OK... fried 2 IGBTs just by having gate drive running and scoping without any power on VBus. Happened while playing around with the frequency of the signal generator while scoping.

After that read the guide for UD 2.7 and specifically the point about C33 again closely. Compared the two schematics and C33 on UD 2.7 should be C11 on UD 2.9. Changed the 1nF cap I had put in according to BOM with an 220pF as suggested in the UD 2.7 guide for coils running above 200KHz. I think that seemed to have inproved the signal at the gates a little. Here it comes now, my first screenshot



This is without IGBTs installed. I guess as 24V gate voltage is over the maximum ratings anyways, any overshoot is likely to kill the gates. Should I also put at least a little power power on the VBus when scoping the gates? Honestly, I am a little bit afraid now to put in and fry another set of brand new IGBTs. Would it make sense to do the testing with lower gate voltage? Like perhaps 15V as in the OneTesla schematics?

Regarding the feedback burden resistor... in the meantime I had thought in the first OneTesla like build I was using a CT with a ratio of 1:300 and a 5W 1kOhm resistor, so now with 1:625 maybe 2 1kOhm in parallel should do the job... so if I'm not wrong I should have 10W 500Ohm now, which seems to be working well. Oscillation starts as soon as I start the interrupter.

Back to the screenshot:

Currently I have 10Ohm gate resistance... I also had tested 20Ohm (without iGBTs installed), which definitely had removed the ringing but not the over/undershoots. Is it OK to have more than 10 Ohm gate resistances? Everywhere I read 5 - 10 Ohm are the values to use.

[davekni]

OK... fried 2 IGBTs just by having gate drive running and scoping without any power on VBus.

That is extremely rare.  Are you certain IGBTs are fried?  Which leads are open or shorted?

I guess as 24V gate voltage is over the maximum ratings anyways, any overshoot is likely to kill the gates.

Looks like you have TVS diodes to protect IGBT gates.  What value are the diodes?  Mads points out that IGBT gate oxide typically doesn't die until roughly 80V even though spec limit is usually +-20V.  Many coils intentionally run Vge at +-24V to achieve slightly higher peak current.

Regarding the feedback burden resistor... in the meantime I had thought in the first OneTesla like build I was using a CT with a ratio of 1:300 and a 5W 1kOhm resistor, so now with 1:625 maybe 2 1kOhm in parallel should do the job... so if I'm not wrong I should have 10W 500Ohm now, which seems to be working well. Oscillation starts as soon as I start the interrupter.

500 ohms will likely be problematic at 300A primary, 0.48A from CT, 240V across burden resistor.  Are you looking at a schematic for secondary current feedback?

Currently I have 10Ohm gate resistance... I also had tested 20Ohm (without iGBTs installed), which definitely had removed the ringing but not the over/undershoots. Is it OK to have more than 10 Ohm gate resistances? Everywhere I read 5 - 10 Ohm are the values to use.

Small (ie. TO247) IGBTs often need more than 10 ohms.  5-10 is good for larger bricks.  If I recall correctly, I've used 33 ohms for TO247 parts.  Depends on IGBT gate capacitance and needed dead time.  Gate resistor slows turn-on while parallel diode makes turn-off fast.
Measuring ringing and over/undershoot requires IGBTs to be inserted to have realistic gate capacitance.  Also requires good scoping technique, probe and its ground clip directly connected to IGBT leads with ground lead against probe, not forming a large loop to pick up magnetic fields.

[Boilerbots]

You could have purchased most parts you need to assemble a fully working DRSSTC through ebay or Aliexpress if you just want to get something running and play around with it. This is what I was thinking when you first started asking about the oneTesla kits. There are quite a few kits of fully working TCs on there.

I know I could have done that... but I didn't... and passed the point of no return months ago.

That is the "Sunk Cost Fallacy" 

For my first coil I wanted to focus on the construction and operation of the whole thing even though I could have spent a massive amount of time laying out a PCB just for my bulk capacitors and the IGBT I selected, however even that is not trivial considering the operating currents involved and trying to minimize inductance.

[ako]

That is extremely rare.  Are you certain IGBTs are fried?  Which leads are open or shorted?

Not yet sure for all of them... one or two I had tested were shorted between gate and emitter.

500 ohms will likely be problematic at 300A primary, 0.48A from CT, 240V across burden resistor.  Are you looking at a schematic for secondary current feedback?

Ehm... nope, I am still on the UD2.9 from the DRSSTC board pack of Profdc. How much voltage should I aim for?

Looks like you have TVS diodes to protect IGBT gates.  What value are the diodes?  Mads points out that IGBT gate oxide typically doesn't die until roughly 80V even though spec limit is usually +-20V.  Many coils intentionally run Vge at +-24V to achieve slightly higher peak current.

Those bigger diodes diodes in series are bidirectional 1.5KE220CA across collector and emitter of the IGBTs. The smaller ones go parallel with the gate resistors, unidirectional 1N5818, which might have been the wrong ones for 24V what I just realize... right?
I think I had bought some bidirectional BZW0631B TVS diodes intended as TVS across gates and emitters which I haven't built in yet. Should I do so? Are those the right ones for that purpose?

[davekni]

Not yet sure for all of them... one or two I had tested were shorted between gate and emitter.

That is consistent with overvoltage on Vge.

Ehm... nope, I am still on the UD2.9 from the DRSSTC board pack of Profdc. How much voltage should I aim for?

All the UD2.7 and UD2.9 schematics I've seen use 51 ohms for feedback burden resistor.  Surprised you saw 500 ohms somewhere.  51 works for most designs.  I described calculating startup in reply 29.

Those bigger diodes diodes in series are bidirectional 1.5KE220CA across collector and emitter of the IGBTs. The smaller ones go parallel with the gate resistors, unidirectional 1N5818, which might have been the wrong ones for 24V what I just realize... right?
I think I had bought some bidirectional BZW0631B TVS diodes intended as TVS across gates and emitters which I haven't built in yet. Should I do so? Are those the right ones for that purpose?

1N5818 is fine for diode across gate series resistor.
BZW0631B is higher voltage than typically used for Vge protection, but will clamp well before 80V.  Much better than no Vge protection.  Would likely have prevented your previous IGBT failures.

[ako]

Alrighty...

First small light and first BOOM with UD 2.9... I SHOULD have considered cooling for the IGBTS just in case of being succesful and getting first light... or... shouldn't have turned all knobs in all directions right away like a lunatic.... but YEAHHH... first light!!!

So... now I have to figure out how to properly put a heatsink on those IGBTs...

Then? Whats next?  I guess tuning the primary... What is the correct way to do that? Another CT for scoping the feedback frequency? Or scope across feedback or OCD connectors?

[davekni]

Another CT for scoping the feedback frequency? Or scope across feedback or OCD connectors?

Most people seem to use an additional CT.  Not necessary presuming your existing CTs are properly made with ferrite (not powered iron) cores.  Scope across the UD.9 burden resistor (51 ohms usually), not directly across feedback CT input.  Scoping across CT input will include phase lead, so not be accurate.

[ako]

I see some music coming from somewhere!

/>
I can’t stop smiling!

[davekni]

Congratulations on getting your coil running!

[ako]

Thanks man!

I definitely wouldn't already be where I am now without all of your support!!! I really appreciate that!

Of course now a few other questions came up... First of all, my last pair of IGBTs is still alive and surviving daily runs of a few minutes. But another batch of 10 are going to arrive today...

So far, I went up to 150V displayed on my variac before I ran the coil, as the display isn't of any usage when the coil runs (just jumps around and shows garbage). I haven't measured the bus voltage during the runs, but as I currently have a voltage doubling config with the two caps over the bridge, I guess at 150V input I already should be over more than 230V right? Just asking because I am more than happy with what comes out at input 150V right now, so I was thinking if I could not use a voltage doubling config and so be able to run the coil directly from mains without having to modify much more than how it is right now. But then I am wondering how I connect the primary to the bridge as it is currently connected to the center point between the two caps in series.

Another question I have is regarding the primary resonant capacitor. I've built the coil like the OneTesla with its 0.068uF capacitance and also used the same capacitor, but what I did differently is I have used 4 of those capacitors in a 2S2P config... don't know why... does that make sense to do so? Or can I save me 3 caps and use them otherwise... which brings me to the next question, can I use those as snubber caps?

Those two huge bus caps are 450V 5600uF each... Are those values more than I need for this size of coil? Can i go for lower values and smaller sized caps?

Ahh... another one: In regards of measuring primary voltage and current during the runs, everyone is speaking of measuring the bridge output? What exactly is the bridge output in that terms? Is it before the resonant capacitor or behind?

I tried to scope the primary current and output voltage with the help of an CT with a 1R burden resistor attached to it which seems to work fine I guess (that's actually what you see on the scope in the video) and a probe attached to the bridge output (before the cap) and then tried to adjust phase lead with an self wound inductor which I can adjust from ~2mH up to ~17mH according to my LCR meter, but I couldn't see anything significantly changing in the waveforms. Is there any tutorial for dummies how to do the scoping (During the primary voltage scoping, I had disconnected ground lead from my scope power cord)

[davekni]

Thanks man!

I definitely wouldn't already be where I am now without all of your support!!! I really appreciate that!

You are welcome!  Glad to be able to help.

So far, I went up to 150V displayed on my variac before I ran the coil, as the display isn't of any usage when the coil runs (just jumps around and shows garbage).

Analog meters are quite useful around Tesla coils   Or digital meters with shielding around them and filters in lines to meter.

I haven't measured the bus voltage during the runs, but as I currently have a voltage doubling config with the two caps over the bridge, I guess at 150V input I already should be over more than 230V right?

Presuming 150V is RMS AC, peak is sqrt(2) higher, 212V.  Voltage doubler will produce 424Vdc (slightly less due to diode Vf) unloaded.  Of course, voltage drops due to loading.  230Vac has 325V peaks.  Bridge rectifier (not doubler) would generate just under 325V unloaded.

But then I am wondering how I connect the primary to the bridge as it is currently connected to the center point between the two caps in series.

Connect half of MMC to Vbus- and half to Vbus+ (2S1P to each of the incoming DC supply rails, which I'm calling Vbus).  Connect primary coil between half-bridge output and both halves of now-split MMC.  In other words, primary coil and MMC need to trade places before splitting MMC into two halves.  (I'm inferring from other statements here that half-bridge output currently connects to MMC which then connects to Vbus center.)

I've built the coil like the OneTesla with its 0.068uF capacitance and also used the same capacitor, but what I did differently is I have used 4 of those capacitors in a 2S2P config... don't know why... does that make sense to do so? Or can I save me 3 caps and use them otherwise.

2S2P provides margin for higher voltage and current and duty cycle, but may be more than you need.

which brings me to the next question, can I use those as snubber caps?

Yes, but not best choice.  Snubber caps (caps from Vbus+ to Vbus- immediately adjacent IGBT connections) are usually higher capacitance and physically smaller.  Short leads and small allow mounting closer to IGBT connections to reduce parasitic inductance.  Multiple parallel small caps can further reduce parasitic inductance of snubber.

Those two huge bus caps are 450V 5600uF each... Are those values more than I need for this size of coil? Can i go for lower values and smaller sized caps?

Likely more than you need.  As with MMC, depends on current and duty cycle.

Ahh... another one: In regards of measuring primary voltage and current during the runs, everyone is speaking of measuring the bridge output? What exactly is the bridge output in that terms? Is it before the resonant capacitor or behind?

Voltage on bridge output (low-side IGBT collector and high-side IGBT emitter) to probe tip.  Probe ground (with scope ground floating) to either Vbus- or to Vbus center tap (center between bulk caps).  Vbus- for "ground" allows probing close to IGBTs which is most accurate.

I tried to scope the primary current and output voltage with the help of an CT with a 1R burden resistor attached to it which seems to work fine I guess (that's actually what you see on the scope in the video) and a probe attached to the bridge output (before the cap) and then tried to adjust phase lead with an self wound inductor which I can adjust from ~2mH up to ~17mH according to my LCR meter, but I couldn't see anything significantly changing in the waveforms. Is there any tutorial for dummies how to do the scoping (During the primary voltage scoping, I had disconnected ground lead from my scope power cord)

There are many posts on the forum about how to scope and about phase adjustments.  Can't think of any tutorials off-hand.  Scoping both the 3-400V half-bridge output and lower voltage CT output requires come care.  Ideally have coax from CT burden resistor to scope input to avoid picking up noise.  Scope probe and ground clip should form minimal loop area and connect close to IGBTs and away from primary coil wiring.

Scope images are much easier to interpret here if you post separate still images, from camera or scope's internal capture capability.  Both overview as in video and zoomed in to see just two or three cycles is helpful.  To interpret current, need to know both burden resistor value (which you provided as 1 ohm) and CT ratio (which I don't see listed).

Does "2mH to 17mH", refer to milihenries or microhenries?  I'm used to "uH" for microhenries and mH for milihenries.

[Mads Barnkob]

which brings me to the next question, can I use those as snubber caps?

Yes, but not best choice.  Snubber caps (caps from Vbus+ to Vbus- immediately adjacent IGBT connections) are usually higher capacitance and physically smaller.  Short leads and small allow mounting closer to IGBT connections to reduce parasitic inductance.  Multiple parallel small caps can further reduce parasitic inductance of snubber.

I wrote about snubber sizing here https://kaizerpowerelectronics.dk/tesla-coils/drsstc-design-guide/snubber-capacitor/

Those two huge bus caps are 450V 5600uF each... Are those values more than I need for this size of coil? Can i go for lower values and smaller sized caps?

Likely more than you need.  As with MMC, depends on current and duty cycle.

To calculate the ripple voltage on your DC link, I went through that here: https://kaizerpowerelectronics.dk/tesla-coils/drsstc-design-guide/dc-bus-capacitor/

[ako]

Hi folks...

no more questions for a while... a good sign, right? I think yes, but one came up a day ago... but first of all, a progress status update. I'm quite happy with what I've built and I'm almost completely finished with the build (mostly worked on building a case and placing everything). I am working with 230V mains, OCD set to 300A and haven't blown my last two IGBTs for a while now.

Now heading to my question. The last technical change I did, was to change the topload with a slightly bigger one. As I moved the coil to another place in the meantime, I didn't have my oscilloscope to hand and used JavaTC to roughly get the new primary tapping point at ~6.5 turns. As my primary unfortunately only has 6 turns, I tapped it at the end and did a test run. Just to mention: I am using the OneTesla SD interrupter running on an Arduino Nano. As you may know, it boots up to Fixed mode. I started that and the first bangs were much quiter than with the smaller topload and my previous tapping point. I was even disappointed in the first moment. Then I went to the midis and started a song. While it was running I started to increase the volume (I guess the on-time) and the first few clicks increased the volume very slightly still giving much less output than before the change but - I don't know - the fourth or fifth click suddenly made the coil go into badass mode and I honestly got scared by the size and length of those new streamers it started to spit out. Then I moved on with increasing the volume and the remaining clicks until full volume felt like giving a more linear response compared to the first few clicks.

So my question basically is, what happens with the new topload and the new tapping point in combination with the SD interrupter and the configured on-times on its first clicks. Why do I get less output on the lower on-times than with my smaller topload and primary tapping point but then suddenly with slightly higher on-times much much more output?

Here are two videos to compare the output at full volume before and after I changed the topload and tapping point.

Before:
https://youtube.com/shorts/fG4AiAPHJRU

After: (By the way: Celebrating myself for having a strike rail installed, was thinking that it was unnecessary... until this point)

/>

[Mike]

The behaviour you're seeing now is consistent with a coil with the primary tuned below the secondary. At low on times the coil spend most of the on time slowly ramping up the voltage in the secondary because of the relatively poor energy transfer between the primary and secondary. Eventually enough energy transfers to the secondary for break out to occur and the arc starts growing, but then you end the on time so you get a smaller steamer.

If you extend the on time the steamer would grow which pulls down the resonant frequency of the secondary so it comes more and more in to tune with the primary. This increases the amount of energy that can be transferred between the primary and secondary so you can grow larger streamers. Eventually the steamer growth would pull the secondary frequency below the primary frequency and energy transfer starts reducing again. More commonly your on time elapses and you terminate the steamer growth that way.

If you had more primary left you could have tuned it lower for even more growth, but you do need to be a little careful because if your secondary isn't pulling energy out of your primary the current can ramp up very quickly, which can result in higher peak currents before the OCD kicks in and disables the coil.

As to why you end up with a lower primary frequency (or higher secondary frequency) than expected, despite JavaTC saying you needed more turns on your primary, I have no idea...

[ako]

Hm…

I can‘t tell (yet) what frequency I ended up with… if anything is lower or higher compared to what JavaTC calculated. All I can tell is that I had to tap the primary at the end of what I have which is 6 turns instead of the JavaTC calculated 6.5 turns. And if I‘m not wrong, the lower the primary turns the higher the resonant frequency which in my case would mean that my primary currently is tuned for a higher frequency than the resonant frequency of my secondary

Another quick test I can do in a few minutes is to modify the interrupter firmware and add another factor to the on-time multiplier...

EDIT:

...which also didn't seem to change the behavior... the first clicks while increasing the volume still give less output than before the change of topload and primary turns.

[davekni]

The behaviour you're seeing now is consistent with a coil with the primary tuned below the secondary.

I was thinking the same thing.  Seems opposite your actual tap being at 6 turns instead of calculated 6.5 turns.  Perhaps there is much more primary lead inductance than modeled by JavaTC.  (Did you include primary lead length in JavaTC input?)  May be worth trying less than 6 turns just in case primary truly is too far below secondary frequency.

[ako]

Now that I seem to have successfully built my first DRSSTC including cases and stuff and haven‘t blown anymore IGBTs for weeks… the next questions come up:



Can I drive a full bridge with the UD2.9. I know it has only 1 GDT output and full bridges seem to all run with two separate but theoretically a full bridge could be driven with a GDT with 4 secondaries instead of two, right.

Though I‘m pretty sure that the amswer is going to be no, I would like to learn the reason why not.

[Manz]

You can run a fullbridge with a single GDT with a primary and 4 separate secondaries like you said.
For example my drsstc also uses a ud2.9 and has no problem driving a skm100 fullbridge at >100khz with a single GDT

[flyingperson23]

As far as I know, a single GDT with 4 outputs is fairly standard. Some drivers have 2 GDT outputs to enable one method of pulse skipping (not the one the 2.9 uses), or sometimes 2 identical outputs in parallel for very large bricks. You won't have any trouble with a single GDT; what usually works for me is using cat5 cable with 4 wires in parallel for the primary and the remaining 4 each as a secondary.

[ako]

OK, next queation came up:

What could be the issue?

I took out the GDT and the half bridge. I wound another GDT using the same type of core and a piece of CAT5 cable as per your recommendation or your tutorial. Then I placed in that and a full bridge with exactly the same parts and values for resistors diodes and caps as I have on my half bridge (both profdc9‘s PCBs from the PCB pack). I reconnected everything as it was with the nicely working half bridge and ran a test:

It is working, but I barely get some output. My „problem“ is, that my oscilloscope is somewhere else currently and that I can‘t look what exactly is going wrong. So maybe you could tell me if there are some obvious reasons for this behaviour when switching from half to full bridge and leaving everything else, as it is?

[flyingperson23]

the obvious one that I can think of is incorrect phasing; i.e. connecting wires backwards to the igbts

[ako]

Wires backwards to the IGBTs? Those are on a PCB… But just to be sure what you mean… a fix would be to turn the feedback transformer or in my case switch the two jumpers on the UD2.9, right?

[flyingperson23]

Yes, definitely try switching the jumpers on the ud2.9; the wrong setting will stop it from working. What I meant was if you mixed up any of the wires to/from the gdt, that may also prevent it from working.

[ako]

I mean… like I already said, it is working. I get output. But much less than with the half bridge board. Do I need to change something in the interrupter code (OneTesla SD) maybe?

Edit:

OK, like expected, switching the jumpers stopped it from working at all.

[davekni]

I mean… like I already said, it is working. I get output. But much less than with the half bridge board.

Lots of possibilities.  One likely issue is that only one side of H-bridge is functioning correctly.

For any significant change such as half-bridge to full-bridge, it is best to scope signals at low voltage before running anything at full bus voltage.  Ideally start with no bus voltage, feed UD2.9 from a signal generator, and scope all 4 Vge signals.  Then apply low Vbus (perhaps 12V) and scope both bridge outputs.  If your bench supply can go higher, by 30V or at least by 60V you should be able to get some coil operation using CT feedback instead of signal generator.  Run all this testing at low duty cycle.  Can all be done without secondary in place.

[ako]

Can a defective mosfet on the UD2.9 be the reason (for coil working but with low output)? Or would it then not be working at all? Because shortly after running the last test with switched phasing and then switching back and letting it run again for 3 4 bangs I stopped the interrupter signal but the system was still powered, so fan spinning and LEds on on the driver. Then all of the sudden lights went out und fan stopped. Status LED of the power supply also off. After a little search I touched a very hot mosfet. I removed it and can power everything normally again. Unfortunately my spare mosfets are somewhere else currently. Tomorrow I‘ll be able to replace it, but as I‘ve asked already, could that dying mosfet be the reason for the low output?

[davekni]

could that dying mosfet be the reason for the low output?

Yes.  As I said, lots of possible issues.  That's why it is good to scope at low power first after any significant change or repair.

[ako]

Indeed, both mosfets on one side of the UD2.9 were dead.

Replaced them, scoped the output to be sure to get proper signals, skipped the low power tests and just gave it a try.

Now I am getting the output I was expecting, but I guess I‘m still detuned currently. Will check that later.

I have some questions regarding the interrupter firmware/on-times/primary current but I‘ll bring those up later when I‘m on the laptop.

[Dominic@TWHV]

Quick suggestion (I did not scroll through everything):

be sure to heatsink your IGBTs, and enclose the driver in some ferromagnetic casing to reduce interferences.

Good luck making it!