Author Topic: CM300 coil build questions  (Read 868 times)

Offline acobaugh

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CM300 coil build questions
« on: July 21, 2019, 05:32:28 AM »
Hey folks!

I've got the itch again to start back up on my first DRSSTC build. Now, this is not my first TC by any means - I've been building and improving my own tesla coils since about  2002. I've recently maxed out my latest design - an 8" SGTC running a pair of 12kV PTs in series/parallel, about 30A+ @280VAC input (see https://labs.cobaugh.io/hv/tesla/8inch-sgtc for full specs). The resonant frequency doesn't allow me to put the system fully in tune without off-axis induction with the current 0.03uF MMC. The whole system was intended to be run off a pole transformer eventually by reconfiguring the MMC for 0.12uF, or using a pair of GE industrial snubber caps, but I doubt that will happen as I've grown tired of hauling all of this heavy iron around when I want to run it outside (despite having a nice big workshop, the rafters even at 10ft are rather limiting for TC use at high power).

I'd like to reuse this secondary, primary, and topload for a CM300DY-24H full bridge drsstc, running up to 1000A (maybe more if folks think I could swing 1200A with this frequency). The secondary+topload have a measured Fres of around 73kHz.

For DC bus I have a pair of CDE 520C series 11,000uF 450VDC stud-mount capacitors, to be configured in a voltage doubler setup.

IGBTs were originally going to be 4x Mitsubishi CM300HA-24H single modules, as there was a time when the single modules were cheaper than the dual modules. Then I found a seller with CM300DY-24H at a very reasonable price, so I picked up 4. Right now I'm leaning towards the dual modules for the ease of bus layout, and generally better availability of replacements.

For the MMC, I think I have two options:
1) I use my existing 20s4p CD942C20P15K MMC and rearrange it so it's 5s16p for 0.480uF, 10kvdc, 216A RMS, 6912Apk.
2) I procure some of the Aerovox RBPS 2uF 1kvdc snubber caps, and set them up in 16s4p for 0.5uF, 16kvdc, 88A RMS, 3416Apk

Driver will be Gao's UD2.7C.

A couple of questions:
1) Is 73khz a low enough frequency to run these CM300s at, at up to 1000A peak (assuming phase lead and such)? Or should I wine a new secondary with thinner wire for a few more inches to get it down a bit? I'm probably also going to build a much larger skeleton topload, which should drop Fres even further.
2) Which MMC option would you run? It seems like some people (Gao, maybe ArcAttack?) run the RBPS snubbers without issue, but the thermals and RMS current capability don't look too good on paper with only 4 strings in parallel.

Offline Mads Barnkob

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Re: CM300 coil build questions
« Reply #1 on: July 27, 2019, 08:51:22 PM »
Welcome to HVF!

You have a solid plan and the HV experience to pull this off, no problems, only new terratory to you is phasing of signals, unstable feedback and EMI problems :)

Both your MMC options are viable, but there is no doubt that the 942C one, with its high RMS current capability, is superior to the RBPS, even though it has a higher voltage rating, once you do the math for a DRSSTC (or use some calculators: http://kaizerpowerelectronics.dk/calculators/mmc-calculator/ ) you will see that you often do not need that high voltage rating for a DRSSTC MMC compared to a SGTC.

For the IGBTs withstanding 1200A at 70kHz, you have to do the math :) http://kaizerpowerelectronics.dk/tesla-coils/drsstc-design-guide/igbts/

36 kHz    1300 A    Powerex CM300DY-24NF    Fabrício Franzoli
42 kHz    1200 A    Powerex CM300DY-24    Dzejwor on 4hv.org
70 kHz    750 A    CM300DY-24H    Hydron on 4hv.org
72 kHz    700 A    CM300DU-24NFH    Gao Guangyan

Looking at these recorded settings, you might be facing some serious switching losses and perhaps you water cool your way out of the problem, or use the single IGBT modules so you have much more surface to dissipate the heat on, if they have good enough specifications to do so.
http://www.kaizerpowerelectronics.dk - Tesla coils, high voltage, pulse power, audio and general electronics

Offline acobaugh

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Re: CM300 coil build questions
« Reply #2 on: September 17, 2019, 05:00:47 PM »
Thanks for the feedback, Mads. I ended up going with the 5x16 array of 942C20P15Ks for my MMC, as I had them on hand and knew the result would be overbuilt for the intended use.

Last night I finished the wiring between my driver and the IGBTs. I'm using a 5.1ohm resistor and 1N5819 schottky diodes in parallel, then 1.5KE33CA zeners across G-E to protect the gates.

I then fed a 65kHz signal into the driver feedback and scoped one of the gates. Waveforms are below. Do these look good? Seems like it's rising fast enough to me, but I'm not sure about the overshoot when going negative. Thoughts?

All photos of the build are here: https://photos.app.goo.gl/p7aRujo5RaAV8J7X8

Waveforms:





Offline acobaugh

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Re: CM300 coil build questions
« Reply #3 on: September 18, 2019, 05:54:23 AM »
First light! Sort of. Hooked everything up, set the primary to about 70kHz (Secondary resonates at about 72kHz), then applied power directly to the bus from a 30VDC 5A linear bench supply. At just about 10VDC, it started resonating first time out! I was a bit surprised that it was that easy. I tweaked phase lead a bit to get rid of any obvious voltage spikes towards the end of the cycle, with just a faintest hint of spikes early on in the cycle where the current is lowest.

I then cranked it all the way to 30VDC. With a sharp breakout point, there's just the slightest hint of corona. With the lights off I could draw a 1-2" arc with a screwdriver, and the fluorescent lights about 4ft above the coil were just starting to glow.

Still surprised it was this easy, but then again I've been carefully planning this for just over 2 months, and testing every component as I go.

What does everyone think of these waveforms?

I think next step is applying higher voltage from either a 600VDC 1.5A Sorenson power supply, or from 240VAC mains through an isolation transformer. Haven't decided yet. This will let me see what's going on at or near design voltage and fine tune phase lead and look for any obvious issues.

Channel 1: Vge of one of the lower igbts
Channel 2: Bridge output
Channel 3: Current through a 1000:1 CT with 10R burden (should be 100:1 ratio, channel is set to 100X)

First capture is without any phase lead adjustment. Rest are with, at varying voltages and on-times.






Offline Mads Barnkob

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Re: CM300 coil build questions
« Reply #4 on: September 18, 2019, 01:35:58 PM »
The GDT waveform is perfect, if it wasn't for the massive undershoot, I get a feeling its related to your 1N5819 schottky diode in parallel for fast turn-off, have you tried to remove it?

Your switching waveforms look fine aswell, do not get scared by the large switching spikes when doing a low voltage test. The output capacitance of the IGBT is larger at lower voltages and thus you will see % ratio larger switching spikes at lower voltages than when you get up at full input voltage. So if you see 50% spikes at 60VDC, do not fear/expect 900VDC spikes at 600VDC in, it will properly be around 10-20% spikes.

Just test with highest possible supply voltage and start out with a very low BPS, like 1BPS and see how it goes. It is better to test at full voltage and just lower BPS, even if there is something wrong, a IGBT brick is specified for high short circuit currents for 1ms, so a single pulse of 200uS high current is not enough to harm the die from too high temperature rise.

Please do post more pictures of the bridge, coil and everything else related to this build :)
http://www.kaizerpowerelectronics.dk - Tesla coils, high voltage, pulse power, audio and general electronics

Offline acobaugh

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Re: CM300 coil build questions
« Reply #5 on: September 18, 2019, 05:08:06 PM »
I included the 1N5819 in parallel because "everyone else was doing it." I've also never seen anyone with undershoot caused by having it, so I'm still not sure that's the cause. I can try removing it on one of the gates just to see, but those connections are rather hard to get to with my layout.

More pics are attached.

I went back and verified I definitely don't have undershoot with the driver/gdt running just a small capacitor and resistor in series on the bench, so the undershoot shows up only when driving the IGBT. It happens on both of the modules in that half-bridge, I'll check the other half-bridge tonight. Possible I have a bad IGBT half-bridge?
















Offline acobaugh

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Re: CM300 coil build questions
« Reply #6 on: September 18, 2019, 06:56:20 PM »

Offline acobaugh

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Re: CM300 coil build questions
« Reply #7 on: September 18, 2019, 07:27:46 PM »
Actually, Gao got almost identical waveforms!

http://www.loneoceans.com/labs/model82/DecTuning.gif
http://www.loneoceans.com/labs/model82/GreenCoil200Atest.png

That makes me feel a lot better about my setup.

Offline acobaugh

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Re: CM300 coil build questions
« Reply #8 on: September 19, 2019, 07:16:20 PM »
Last night I removed the secondary and put a pan of water in its place. I then fed wall power in via a 1:2 isolation transformer (120VAC in, 240VAC), so I very nearly reached max operating voltage on the bus. I kept the input voltage under ~70VAC, because the OCD was starting to trip continuously. OCD is still set at ~400A for now.

So far so good. I zoomed in to one of the last half cycles and tweaked the phase lead so minimize ringing and smooth out the voltage transition.

Then of course I had to power it up "for real". Input voltage never went beyond 70VAC or so, and input current seemed to peak out at around 10A (measured on input side of variac). This puts peak power draw at around 1.2kVA. I forget the exact parameters, but I believe at a really high break rate playing MIDI, it was easily hitting the screen 3.5 feet away. This easily makes it more efficient than any spark gap coil I've built.

More tuning is necessary. The secondary system is at ~72kHz, and the primary is only a few kHz lower than that. Probably need to move the primary out another half to full turn to drop it closer to 66kHz or so.

I also need to wait another day or so for the enclosure for the interrupter to be back from powdercoating. Starting to get see some issues with interference, and it's rather difficult to adjust in the dark without shorting something out! Interrupter is Gao's MIDI2, plus an Adafruit 1000C boost converter/battery management board, plus my own custom board with an astable 555 and a bunch of NPN transistors that lets me add burst mode on top of what the MIDI2 is providing (with separately variable on/off time and two ranges to select from).

Scope shots, pics, and a couple videos:

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Offline Mads Barnkob

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Re: CM300 coil build questions
« Reply #9 on: September 19, 2019, 09:49:15 PM »
It is a very nicely built coil you have there, that bridge layout and compactness, can not get much lower inductance than that!

Congratulations on your first light!

Regarding the negative peak on the gate signal, maybe its inherent for the steve ward UD? Are all gates the same? To rule out its something like voltage drop on the DC bus negative rail or some weird crosstalk from the inverter driving a load.
http://www.kaizerpowerelectronics.dk - Tesla coils, high voltage, pulse power, audio and general electronics

Offline davekni

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Re: CM300 coil build questions
« Reply #10 on: September 20, 2019, 07:05:19 AM »
As Mads mentioned, the diodes in parallel with the gate resistor are likely the primary cause.  It's not their capacitance, but rather that there is no damping resistance for the gate falling resistance.  The circuit becomes the leakage-inductance of the gate drive transformer and wiring combined with the IGBT gate capacitance.  I wouldn't expect the undershoot to change much with bus voltage, since only a tiny fraction of the undershoot appears to come from gate-collector capacitance (as can be seen from the post-drive waveforms, while the collector is still toggling, but the gate drive signal is off).  The only issue this undershoot may cause is violation of the peak Vge specification for the IGBT.  I haven't looked up those specs, but peak of +-30Vge is common.

The options that come to mind if the undershoot needs reduction:
1) Remove the diodes or add some series resistance to the diodes, perhaps 2 ohms if that's enough.  Of course, this slows turn-off time.  Does the driver have any option to add dead-time (delay turn-on from turn-off)?
2) Reduce gate drive transformer leakage inductance.  Looks like your construction is already good, so that would be tricky.
3) Reduce the TVS clamp voltage to clamp the undershoot more.

Good luck!  Looks well designed - especially the stacked-copper-plate Vbus/ground connections from bulk caps to H-Bridge!

BTW one other major-redesign option is to have floating gate-drive power rails, and buffer the gate-drive signals at the gates.  That's what I've done on my new 2600A DRSSTC primary, using 10 paralleled TO247 IGBTs for each H-Bridge switch.

David Knierim

Offline acobaugh

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Re: CM300 coil build questions
« Reply #11 on: September 20, 2019, 05:43:13 PM »
The datasheet for the Mitsubishi CM300DU-24H's only specifies Vge as +/-20V, so I'm already exceeding that by using a 24VDC supply and driver. The undershoot was there even without anything on the bus, though some of my scope shots makes it look a lot less at higher voltages on the bus. As I've noticed, others are driving CM300s in a similar fashion with similar undershoots without issues. I have plenty of spare silicon, so I think I'll let it rip and see how it fares. The UD2.7C doesn't have any dead time functionality, so I think I'd rather er on the side of caution. And because it's a pain to get to the gate connections without disassembling half the bridge... Something I want to address in the future.

I did measure the GDT leakage inductance at one point, but apparently didn't write it down. I seem to recall it being relatively low, and so kept moving forward with the design.

The gate clamps are... 1.5KE33CA I believe? I think I also have some P6KE30CA I could use if I wanted to. I may swap them in if I have time before the "big day" tomorrow (end-of-summer party).

Yesterday I received a lot of 6 Mitsubishi CM600HA-24H's off of ebay. I'll possibly be looking into gate drivers for that project...

I also completed the interrupter last night, after much debugging. tl;dr atmega's don't like voltage transients on Vcc (caused by the astable 555 charging/discharging its RC network). Had to add a 1000uF electrolytic to Vcc to smooth out the supply from the adafruit powerboost 1000C dc-dc boost converter.

Gao's MIDI2, a custom 555 board to further interrupt the output from the MIDI2 to provide two ranges of "burst mode". 1S LiPo power, usb charging, status LEDs. I think it came out quite nice.










Offline Mads Barnkob

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Re: CM300 coil build questions
« Reply #12 on: September 20, 2019, 08:06:32 PM »
The datasheet for the Mitsubishi CM300DU-24H's only specifies Vge as +/-20V, so I'm already exceeding that by using a 24VDC supply and driver. The undershoot was there even without anything on the bus, though some of my scope shots makes it look a lot less at higher voltages on the bus. As I've noticed, others are driving CM300s in a similar fashion with similar undershoots without issues. I have plenty of spare silicon, so I think I'll let it rip and see how it fares. The UD2.7C doesn't have any dead time functionality, so I think I'd rather er on the side of caution. And because it's a pain to get to the gate connections without disassembling half the bridge... Something I want to address in the future.

http://kaizerpowerelectronics.dk/tesla-coils/drsstc-design-guide/igbts/

Maximum Gate-to-Emitter Voltage (VGE)

The gate voltage is limited by the thickness and characteristics of the gate oxide layer. Though the gate dielectric rupture is typically around 80 volts, the user is normally limited to 20 or 30V to limit current under fault conditions and to ensure long term reliability.

It is normal practice to drive IGBTs at +24VDC with the Steve Ward universal driver and clones of it that most use. The reason for the gate voltage limit is not so much for protecting the gate itself, it will first break down at some 80 Volt. Higher gate voltage means higher currents can be conducted through the Collector-Emitter. We take advantage of this by pushing the gate a little over its rated voltage to allow us to conduct higher currents through the IGBT, at the cost of higher switching losses. As explained by manufacturers in the following.

It is important to note however that IGBTs exhibit relatively high gain even at high gate-emitter voltage. This is because increasing the flow of electrons by increasing the gate-emitter voltage also increases the flow of holes. The gain of a high voltage power MOSFET however is very insensitive to gate voltage once fully on.
http://www.kaizerpowerelectronics.dk - Tesla coils, high voltage, pulse power, audio and general electronics

Offline Hydron

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Re: CM300 coil build questions
« Reply #13 on: September 20, 2019, 11:10:54 PM »
I've only just gotten around to reading this thread, but looks like great work, thanks for the pictures and build commentary. A few quick comments:

- What you though about building the coil and it working straight away off a bench power supply is pretty much my experience too - I also put a lot of work into getting things right but it suddenly just working first try without any exploding silicon was still a bit of a shock!

- I wouldn't be too afraid of trying to reach your ~1000A goal with CM300s seeing as you have spares - with an 8" coil you probably want to be pushing some decent current, and expect 2-2.5m or so of streamer length (I get a little over 2m with my 160mm dia. coil using the same CM300s at up to 80kHz). Just be aware that the OCD will not shut off the gate drive until the end of a full cycle - if current is ringing up very fast then there can be overshoot beyond what you calculated when setting the trip current potentiometer.

- Have a go at tuning the primary both above and below the secondary frequency, especially when playing around with a midi interrupter/controller. They can behave quite a bit differently regarding arc growth vs on-time - I found lower tuning "angrier" once it got going, but needed a decent on-time to build enough current to initially break out and then for the streamer to bring the secondary into tune, whereas upper seemed to be calmer but more consistent for MIDI playback. Your mileage may vary, but try both!

- Finally regarding the gate drive waveform I'd make the following suggestions (some repeating what others have suggested):
* When using a schottky diode to speed up turn-off, also include a small resistance that is not bypassed by it - I have used ~1 ohm in my case (though I have also omitted it with good results too). For turn-on I used 5 ohms, but didn't do much testing of other values - just checked that the gate waveform looked reasonable.
* For the gate clamp, I would use a ...24CA or ...27CA TVS diode - while the breakdown voltage is pretty close to the 24V gate voltage you're using, the clamping voltage rises quite a bit with current so you want to run as close to the operating voltage as is reasonable. Given the very low duty cycle, I wouldn't worry too much about them getting hot or anything. My experience is that the 24V diodes still allow overshoots reaching towards 30V, though I don't have any scope caps of the CM300s to refer to.
* If you want to maximise the gate drive performance, ensuring that the leakage and wiring inductance of the GDT and it's connections is as low as possible will also help. It's probably not so critical with larger slower IGBTs like the CM300, but I wouldn't make the wiring longer than needed.
* Finally the general shape of the waveform is pretty much what I'd expect, no need to worry too much if the coil is running well! Even if you reduce the lifetime of the IGBTs by a thousand times it's probably still not an issue (unless you're giving commercial performances).

Offline acobaugh

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Re: CM300 coil build questions
« Reply #14 on: September 25, 2019, 05:26:35 AM »
Greetings, all!

We had a hugely successful party Saturday night. Ran the gamut of MIDI songs, probably 30+ minutes of run time, and everything ran nice and cool. It regularly hit the cage of death at ~80 inches away. I think it easily would have hit 7ft even if we had backed up the cage just a few more inches, but we wanted to keep hits up for dramatic effect.

That being said, some observations. I couldn't really run the power up much more than 120VAC in (off of a 0-280VAC variac) without having the OCD trip continuously. Remember the bus is voltage doubled, so this was just half of the design voltage. Pulse width was also barely 45uS most of the time. OCD was set at 4.08V, so 800A (5.1ohm burden, 50:20:1 OCD CT). I captured just one scope shot, representative of how it looked for most of the evening. Running in normal interrupter mode, at up to 300BPS, it would only reach out to maybe 5-6ft. It needed a much higher BPS to hit 7ft, which sort of tells me my pulse width just isn't long enough for good spark growth, so I have to compensate by just firing more often (and my DC bus has 1.2kJ of energy, so plenty of power to supply high bang rates).

My thoughts on this revolve around primary surge impedence, and possibly being tuned a bit too low. Secondary circuit Fo is around 72kHz. Primary was tuned to about  66kHz. However, that left me at just 3-3/4 turns on the primary. I measured the primary coil and cap tonight at 12.6uH and 0.534uF. That puts my impedance at somewhere between 4.8ohms and 5.2ohms, depending on which number I want to believe more. Oscilloscope+function generator told me primary was at 66kHz, but those numbers tell me it was closer to 61.5kHz, so I have error somewhere.

Anyway, with the primary tuned potentially lower than it should, and being of such a high impedance. Wisdom seems to be impedance should be between 5-10x inverter output impedance, which in my case puts me around 5-10ohms. In any event, observation leads me to believe that my current is ramping up much too quickly for good spark growth, and I should try to increase the primary impedance.

My plans so far are, in order of priority:
- Rework the gate drive electronics to get a much better gate waveform
- New secondary and larger topload to get my Fres down to ~44kHz from the 72kHz it's at now
- New more compact primary that's easier to adjust. Existing primary has almost 15T, originally designed for SGTC operation where the wisdom was that high impedance primaries reduced spark gap losses.

Does my thinking sound right here, on the impedance causing me to hit OCD before the arcs can really grow? If I turned the input voltage up all the way, the OCD was on pretty much all the time after just 2-3 rf cycles (just ~30uS at this frequency!)



And videos!

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Offline Hydron

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Re: CM300 coil build questions
« Reply #15 on: September 25, 2019, 07:10:00 PM »
Before going to the effort of rebuilding the primary, is it possible to try a lower value of tank capacitance to allow a higher impedance test using the existing primary? I'd also suggest testing tuning it higher too, including above or near the secondary resonance (probably only practical with a reduced tank capacitance).

Other than that, great to hear it ran successfully, even without optimisation.

Offline davekni

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Re: CM300 coil build questions
« Reply #16 on: September 26, 2019, 05:04:24 AM »
The primary capacitance value is likely correct, as decent polypropylene capacitors don't change much with frequency.  Primary inductance depends some on the measurement frequency due to skin and proximity effects, higher at low frequencies.  If your measurement was from a meter running at 10kHz or below, that could explain the difference.   (Secondary inductance will be more flat with frequency since the wire diameter is so small compared to the coil size.)

Another consideration is that the resonant frequencies of the coupled system aren't the same as the primary alone, one above and one below.  Try driving the primary circuit without the secondary in place (or at least without the top load, which will get you close).  That will show the actual primary resonant frequency.

As Hydron suggested, I'd move your primary tap to the outside edge, then lower primary capacitance to get the resonant frequency back up.  That may provide sufficient increase in primary impedance.

Congratulations on a good first show!
David Knierim

Offline acobaugh

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Re: CM300 coil build questions
« Reply #17 on: September 26, 2019, 05:13:42 AM »
Yeah, I can remove a whole MMC layer to get 0.36uF, or disconnect individual 5s strings to reduce it by 0.03uF at a time.

I think what I may try next is set the input voltage, BPS, and PW to a fixed value, then sweep various tuning points and grab a scope image of primary current for each, noting arc length and whether OCD is tripped.

I re-measured the secondary this evening without the primary in place. With the 7x34 top load, it's right at 70kHz, much lower than I originally recorded in my notes over the years. I'll probably start with the primary at 70kHz, then sweep one or two turns above and below and plot out the results.

If that shows that I'm not too far off, I may try dropping primary C to get the impedance up and see how it runs. I should have plenty of headroom on the RMS amps to allow for losing an entire MMC layer. The current 5s16p config gives me 216Arms at 10kvdc.

I also want to say thanks to everyone that's chimed in thus far. I'm at the point of wanting to sell off most of my high voltage transformer stock due to the success I've had lately. I still have a hard time believing everything worked first try, and this is my first solid state coil ever.

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Re: CM300 coil build questions
« Reply #17 on: September 26, 2019, 05:13:42 AM »

 


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October 14, 2019, 04:23:56 PM
post Re: How to measure voltage output of AC flyback transformer
[Transformer (ferrite core)]
klugesmith
October 14, 2019, 07:27:49 AM
post Re: DRSSTC with litz-wire primary and 40 x TO247 IGBT H-Bridge
[Dual Resonant Solid State Tesla coils]
T3sl4co1l
October 14, 2019, 07:10:39 AM
post Re: How to measure voltage output of AC flyback transformer
[Transformer (ferrite core)]
MRMILSTAR
October 14, 2019, 05:43:57 AM
post Re: so far video
[Spark gap Tesla coils]
davekni
October 14, 2019, 05:40:27 AM
post Re: Drsstc 4 (new direction)
[Dual Resonant Solid State Tesla coils]
davekni
October 14, 2019, 05:23:48 AM
post Re: Drsstc 4 (new direction)
[Dual Resonant Solid State Tesla coils]
oneKone
October 14, 2019, 04:37:49 AM
post Re: How to measure voltage output of AC flyback transformer
[Transformer (ferrite core)]
davekni
October 14, 2019, 03:47:03 AM
post Re: How to measure voltage output of AC flyback transformer
[Transformer (ferrite core)]
klugesmith
October 13, 2019, 11:05:25 PM
post Re: How to measure voltage output of AC flyback transformer
[Transformer (ferrite core)]
davekni
October 13, 2019, 09:29:25 PM
post Re: How to measure voltage output of AC flyback transformer
[Transformer (ferrite core)]
MRMILSTAR
October 13, 2019, 04:43:47 PM
post Re: My first DRSSTC on bricks
[Dual Resonant Solid State Tesla coils]
davekni
October 13, 2019, 07:04:20 AM
post Re: How to measure voltage output of AC flyback transformer
[Transformer (ferrite core)]
davekni
October 13, 2019, 07:00:57 AM
post Re: DRSSTC with litz-wire primary and 40 x TO247 IGBT H-Bridge
[Dual Resonant Solid State Tesla coils]
davekni
October 13, 2019, 06:36:13 AM
post Re: DRSSTC with litz-wire primary and 40 x TO247 IGBT H-Bridge
[Dual Resonant Solid State Tesla coils]
Weston
October 13, 2019, 12:41:07 AM
post Re: My first DRSSTC on bricks
[Dual Resonant Solid State Tesla coils]
Hydron
October 13, 2019, 12:17:39 AM
post Re: My first DRSSTC on bricks
[Dual Resonant Solid State Tesla coils]
Laci
October 12, 2019, 11:21:39 PM
post How to measure voltage output of AC flyback transformer
[Transformer (ferrite core)]
MRMILSTAR
October 12, 2019, 08:37:36 PM
post Re: DRSSTC with litz-wire primary and 40 x TO247 IGBT H-Bridge
[Dual Resonant Solid State Tesla coils]
davekni
October 12, 2019, 06:57:55 PM
post Re: so far video
[Spark gap Tesla coils]
thedoc298
October 12, 2019, 05:28:01 PM
post Re: 220ac to 440dc 5a boost convertor
[Voltage Multipliers]
rustedone
October 12, 2019, 04:58:28 PM
post Re: My first DRSSTC on bricks
[Dual Resonant Solid State Tesla coils]
Netzpfuscher
October 12, 2019, 03:53:12 PM
post Re: My first DRSSTC on bricks
[Dual Resonant Solid State Tesla coils]
Laci
October 12, 2019, 02:12:59 PM
post Re: 220ac to 440dc 5a boost convertor
[Voltage Multipliers]
rustedone
October 12, 2019, 10:43:48 AM
post Re: DRSSTC with litz-wire primary and 40 x TO247 IGBT H-Bridge
[Dual Resonant Solid State Tesla coils]
ScottE
October 12, 2019, 07:38:47 AM
post Re: Help for people buying the "12-48 Volt 1800/2500 Watt ZVS induction Heater"
[Electronic circuits]
davekni
October 12, 2019, 06:16:12 AM
post Re: DRSSTC with litz-wire primary and 40 x TO247 IGBT H-Bridge
[Dual Resonant Solid State Tesla coils]
davekni
October 12, 2019, 05:52:51 AM
post Re: so far video
[Spark gap Tesla coils]
MRMILSTAR
October 12, 2019, 05:13:28 AM
post Re: Problems with my first DRSSTC
[Dual Resonant Solid State Tesla coils]
davekni
October 12, 2019, 04:41:19 AM
post Re: so far video
[Spark gap Tesla coils]
thedoc298
October 12, 2019, 02:58:19 AM
post Re: so far video
[Spark gap Tesla coils]
thedoc298
October 12, 2019, 02:56:17 AM
post Re: so far video
[Spark gap Tesla coils]
MRMILSTAR
October 12, 2019, 02:38:43 AM
post so far video
[Spark gap Tesla coils]
thedoc298
October 12, 2019, 12:26:44 AM
post Re: Help for people buying the "12-48 Volt 1800/2500 Watt ZVS induction Heater"
[Electronic circuits]
T3sl4co1l
October 11, 2019, 11:33:19 PM
post Re: My first DRSSTC on bricks
[Dual Resonant Solid State Tesla coils]
Netzpfuscher
October 11, 2019, 11:17:17 PM
post Re: DRSSTC with litz-wire primary and 40 x TO247 IGBT H-Bridge
[Dual Resonant Solid State Tesla coils]
Hydron
October 11, 2019, 10:06:32 PM
post Re: My first DRSSTC on bricks
[Dual Resonant Solid State Tesla coils]
Laci
October 11, 2019, 09:03:38 PM
post Re: 220ac to 440dc 5a boost convertor
[Voltage Multipliers]
rustedone
October 11, 2019, 07:32:57 PM
post Re: 220ac to 440dc 5a boost convertor
[Voltage Multipliers]
rustedone
October 11, 2019, 07:22:56 PM

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