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Dual Resonant Solid State Tesla coils (DRSSTC) / Re: Almost finished DRSSTC 5ft arcs!
« on: May 16, 2023, 02:29:47 PM »
Very nice work! Well done
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Dual Resonant Solid State Tesla coils (DRSSTC) / Re: Almost finished DRSSTC 5ft arcs!« on: May 16, 2023, 02:29:47 PM »
Very nice work! Well done
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Dual Resonant Solid State Tesla coils (DRSSTC) / Re: Problems with my simple DRSSTC« on: January 05, 2023, 06:32:35 PM »
Hi Stoppi, I do not have enough knowledge to answer your questions properly so am hoping the others will jump in and help :-)
This looks more like an interrupted SSTC than a DRSSTC to me? (which I have never played with ) The 'high tone' of your spark output is a combination of the fres of your secondary and the 150hz from your interrupter. Considering that you are getting output from your coil at lower voltages and current, I would probably think that your coil coupling is way too tight. Have you tried a larger diameter primary form and/or moving the primary lower? BTW: Congrats on your build 3
Dual Resonant Solid State Tesla coils (DRSSTC) / Re: Grounding« on: October 18, 2022, 09:59:44 AM »
Hi there,
I believe you will find all of your answers here: https://kaizerpowerelectronics.dk/tesla-coils/drsstc-design-guide/grounding-circuit-protection-and-emi/ :-) 4
Dual Resonant Solid State Tesla coils (DRSSTC) / Re: Max on-time calc« on: October 18, 2022, 09:57:07 AM »Maybe method 3 here: https://kaizerpowerelectronics.dk/tesla-coils/drsstc-design-guide/mmc-tank-capacitor/ Thanks Mads, yes, that looks like the calculation base I remembered :-) 5
Dual Resonant Solid State Tesla coils (DRSSTC) / UD2.7C failure?« on: October 17, 2022, 02:20:33 PM »
UPDATE: Ignore the below, seems that a gremlin got into my psu with the single minded purpose of stressing me out for no reason. UD2.7 is just fine :-)
Greets all, Finally got my new dual bridge built and installed only to find that my UD2.7C (SMT version) is dead! Now I don't know what to think ... did my bridge die from IGBT failure or did my driver die and cause my bridge failure??? Anyways ... I'll pull the driver out this evening to have a look but wanted to throw the question out there: Has anyone had a perfectly operational UD2.7C that, for some reason, failed? if so, what failed? Mine is a full short on the power pins and pulls the PSU down into overcurrent protect. No obvious component damage ... Cheers Grant 6
Dual Resonant Solid State Tesla coils (DRSSTC) / Max on-time calc« on: October 11, 2022, 02:40:38 PM »
Greetings all
I am convinced that I had found some formulae a couple of years ago that alllowed me to calculate the max interrupter on-time possible for my DRSSTC taking into account, if I remember correctly, the bps, the bus capacitance (energy before voltage sag) and the max permissable temp rise in the IGBT's .... Anyone? Thanks in advance G 7
Dual Resonant Solid State Tesla coils (DRSSTC) / Re: Bridge failure - which went first, board or IGBT?« on: September 05, 2022, 02:39:00 PM »Sounds like a good design. Yes, in general you should be fine at high repetition rate since you have kept duty cycle constant. However, two possible high-repetition-rate issues come to mind: Hey Dave, LOL thank you, I am quite proud of my interrupter :-) You see, this is exactly why I love this forum so much, post what initially sounds like a no brainer question and all of a sudden you find yourself learning about things you would never have thought of before Certainly true in my case as I would not have given the anti-parallel diode a seconds thought! I'll have to go do more homework! Happy days. Re the repairs ... nope, I'll be scrapping that board thank you! Apart from that I do have spares of that board, I'm using the opportunity as an excuse to put my dual bridge board to the test :-) pics later 8
Dual Resonant Solid State Tesla coils (DRSSTC) / Re: Bridge failure - which went first, board or IGBT?« on: September 04, 2022, 04:14:43 PM »I've seen identical failures on my bridge. I can't see a way that a PCB failure would cause the IGBT to fail. When the PCB fails it becomes an open circuit and prevents further current from flowing. When the IGBT fails however they normal fail short circuit. In this case there's nothing to stop very high currents flowing which will destroy the PCB. Hi Mike, thanks for that! It does of course make sense that it was the IGBT's that went before the board, I just wanted to throw it out there only because I had found no physical damage to them at all, and there are always lessons to be learned :-) Thanks also for your answer on the repitition rate. As I am using my own digital ucontroller driven interrupter, it does reduce the on time in track with the increasing bps thus I can never exceed my set max duty cycle. ie. if duty set at 10% bps=200 pw=500 but at bps of 2000 the pulse width will have droped down to just 50usec. Thus, I figured I was relatively in the clear to push the repitition rate higher than 'usual' :-) ? 9
Dual Resonant Solid State Tesla coils (DRSSTC) / Bridge failure - which went first, board or IGBT?« on: September 01, 2022, 10:31:12 AM »
Greetings and salutations
The last time I ran my coil I overdid things slightly and was rewarded with the usual flash and bang, which I assumed at the time meant that I had blown an IGBT. Testing the bridge, I have indeed lost 3 IGBT's, however, unlike the last time that I blew an IGBT, this time none have any physical damage to their casings. I am attaching photos of my board showing that the tracks off Q4 (full bridge) on both the collector and emitter have been vaporised. My question is, could this have been a board failure due to an overcurrent/overvoltage/overbps, or, would the failure of the IGBT have caused the board damage? Secondary question: My coil runs beautifully at very high bps (1500 to 1800) and when it blew, I was likely pushing the bps past 1800. Could this have caused the failure, or, is high bps ok as long as voltage and current are within limits? Thanks for your comments in advance :-) Grant 10
Dual Resonant Solid State Tesla coils (DRSSTC) / Re: Project: FreakyDRSSTC MK1« on: November 04, 2021, 02:07:34 PM »GrantV, Hi there. I used standard 1oz copper and all seems to be working well. 11
Dual Resonant Solid State Tesla coils (DRSSTC) / Re: Interrupter frequency?« on: October 21, 2021, 12:37:00 PM »
Hey Kevin, lol thanks for that and well done for figuring out the problem :-) As I have since replaced that controller with a UD2.7C, built my own interrupter and am the proud owner of a MidiStick, I doubt that I will need to go back and fix this controller, but it's good to know that there is a way to get it working if I ever need to throw something together for a small project in the future 12
Dual Resonant Solid State Tesla coils (DRSSTC) / Re: What is BPS?« on: June 28, 2021, 10:32:14 AM »He was asking about frequency response to 20 khz which is at the upper limit of human hearing. This implies an expectation of high fidelity sound from a Tesla coil. If this is indeed the case I informed him that his expectation was unrealistic and why. I rarely use CDs but even though they are "old skool" as you say, they are still the highest fidelity form of music playback technology available to the average consumer. If the idea of an optical disc bothers you does FLAC technology with flash drive storage comport with your vision of modern high fidelity playback? If not, then what? Either CD or FLAC technology provides the same sound quality. Hi Steve, LOL I am sorry if you missed the at the end, I was hoping my comment would come across as humorous and was absolutely not intended as a slight :-) 13
Dual Resonant Solid State Tesla coils (DRSSTC) / Re: What is BPS?« on: June 27, 2021, 06:12:18 PM »BPS has been thoroughly explained. Your concern about a frequency range of up to 20 khz is pointless. The music played with transistor tesla coils is full of harmonics and other distortion. You are essentially listening to a series of square wave pulses. The fundamental frequency dominates so you can play music on them and recognize the tune. Just don't expect any sort of high fidelity sound. If you want high fidelity sound, go into your living room and listen to a CD on your stereo equipment. Good grief Steve, that's a little rough isn't it! Stay on topic and at the very least point him in the direction of a CW SSTC or maybe a class E .... BUT REALLY ... sending anyone off the beaten track to old skool nonsense like a CD player on a HIFI is just bang out of order 14
Dual Resonant Solid State Tesla coils (DRSSTC) / Re: 1000 to one« on: June 25, 2021, 10:21:16 AM »The yellow wire is wound 31 times around the core plus one loop around the other core with 32 turns of red wire. The two red wires go to in input of the bridge of the 2.7c. Or in my case my test bridge and a 50uf cap and 5 ohm burden. The wire going through the yellow has 200 amps at 60 hz flowing. At 200 amps I am getting 11 mv across the 5 ohm burden. Got to be doing something stupid, this is not hard. Thank you and hope you spot something in picture. Thanks for the pic. No, that looks absolutely perfect and it looks like you are using the same cores as I am so all should be good. BUT, as John has mentioned, I have never tested a CT like this at 60Hz so this could well be your problem. 15
Dual Resonant Solid State Tesla coils (DRSSTC) / Re: 1000 to one« on: June 24, 2021, 08:01:26 PM »
Hi there,
At 1000:1 and 200A over a 5ohm burden you should be getting 200mA x 5ohm = 1Volt Just checking your CT construction: You do have the last turn (or any 1 of the 32 turns) of the first rings 32 turns going around both rings and then the 2nd ring has 32 turns with the leads coming out and going to the UD2.7C? ie. 2 lengths of wire in total and not 3? 16
Dual Resonant Solid State Tesla coils (DRSSTC) / Re: Choosing an NTC for inrush current limiting« on: June 24, 2021, 04:54:25 PM »There's little reason to keep the inrush as low as 10A. Uncontrolled inrush is usually in the thousands of amps, if you limit the inrush to the high tens to low hundreds of amps, you should be fine. If you want to be conservative, a B-characteristic circuit breaker will handle minimum 3 times nominal current for a few seconds, so you could start with 40 amps for example. And since we're talking about seconds time-scale rather than microseconds, you can use the RMS voltage to calculate the current. This gives a minimum of 6 ohms, so 10 would be fine. Many breakers will be C- or D- characteristic, and the time to charge the capacitor will be in the low milliseconds, so you could likely get away with 4.7 or even 3.3 ohms as well, but if you can get a 10 ohm NTC with the right energy and voltage rating you should be good. Hi Anders, thanks for that! I had assumed that the breaker would immediately trip at anything over it's rated current. Your explanation makes sense and gives me a far clearer idea of how to handle the inrush current 17
Dual Resonant Solid State Tesla coils (DRSSTC) / Choosing an NTC for inrush current limiting« on: June 24, 2021, 02:30:26 PM »
Hi there,
I am struggling to find an NTC for my coil and wondering if I might have miscalculated my requirements. My inverter is full wave rectified 230V mains and I have 3300uF bus capacitance. If I use 325.22V as my peak voltage I get 175joules as my energy so an NTC with max energy rating of 250J should be fine. As my supply is from a 13Amp socket, I could use 10A as my max inrush current and that would give me a R@25degC of 32.522 ohms (nearest NTC is 33ohms so all good) However, if I look for NTC's with a max steady state current of between 13Amps and 15Amps, the max I can find are 10ohm thermistors. Am I doing something wrong or is it normal to use multiple NTC's in series? Do you have any recommended NTC's? OR ... is there a better way? OH .... another question: If I do not bypass the NTC after power up and choose to rather leave it in circuit, I take it that once it has charged the bus capacitors, it is going to start cooling (before I start the coil from my interrupter) which would mean that I would likely discharge my bus caps almost entirely before the NTC kicks back into action? and the same would happen between every run? I am probably just explaining to myself why not bypassing the NTC is a bad idea LOL .... or is the NTC fast enough for this to not be a consideration? Is there a way to configure a relay on the inverter as a delayed bypass WITHOUT using low voltage components? 18
Dual Resonant Solid State Tesla coils (DRSSTC) / Re: Tuning / Testing« on: June 23, 2021, 11:49:33 AM »
Nice one Alan,
I'll certainly give that a try the next time I get to firing up my coil, if I can find a way to properly shield my scope! I was actually considering doing something similar to this anyway so it is a good fit :-) I was simply going to scope the secondary frequency at max spark length using the antenna method you have used and then compare that to my primary tuned frequency (off-line) to see what the difference was. 19
Dual Resonant Solid State Tesla coils (DRSSTC) / Re: Felix's DRSSTC« on: June 22, 2021, 10:37:39 AM »
Wow, a perfectly EXCELLENT coil! Well done Felix :-)
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Dual Resonant Solid State Tesla coils (DRSSTC) / Re: SKM100 Mini DRSSTC« on: June 09, 2021, 10:29:11 AM »
Hey Alan,
That looks EXCELLENT! Very nice work you did there :-) I have not seen the use of the plumbing support before. It is an excellent idea ... wish I had thought of that :-) |