OneTesla Clone ** Urgent help needed!!

[TonyHV]

Hi Guys,

We are a team of engineering students, working on power electronics, and chose Tesla Coil DRSSTC as a graduation project, and decided to do a design similar to oneTesla (the first design with acrylic box, not the oneTesla TS), so and after many trials, we failed to find any PBC design for the kit, and decided to purchase the electroic PCB of the shelf, and build our coils on our own.


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After having a secondary wind up, 3 inch PVC pipe, of 25cm of 0.15mm copper wire, with 5*20 cm toroid topload, the resonance frequency turned to be 290Khz (the design was suggested by some coiler).


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For the primary, I made a flat coil, I used 2.5 mm solid copper wire 3.5 turns with 2mm spacing, which turned to be at 291Khz of resonance.


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The Resonance for each is determined by scope-generator method, and each frequency for primary and secondary is determined separately.

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For the interrupter I used also a ready made board, which fiber optic cable


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The Board mainly came with half bridge of 2 IGBTS of G4PC50UD, and after they fried I changed to use 2 40N60's.

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At my first operation ever (no tuning), I had a light pulp flashing as the interrupter fires, but no sparks at all, and the state remained like so forever, later on , and after tuning, I get this:

at 55VAC the pulp flashes, but tiny sparks (less than 0.5 CM).
at 110VAC the pulp flashes, but little bigger sparks (1 CM) drawn by a screw driver.
at 220VAC (15 A) the board dies and a short circuit happens on the supply rails , then I have to change the IGBTs!!!

We are fairly new to tesla coils, we haven't done any math, and we don't know where to start debugging or what mistake we could probably do, we tried watching Mads video, Mads guide, Steve's guide, and many other readings, but we still don't know where to start fixing the problem , or what is really going on here !

Any advice? we are close to the deadline, yet we are totally lost.

[Fumeaux]

Hello and welcome!

Can you pls provide the schematic or atleast the link from where you got the bord?

I'm not sure about the 40N60s and if they will work for this application. (I'm not even sure what they are, I'd use the same part to replace it)

1.) Read :https://onetesla.com/tutorials http://www.onetesla.com/oneTeslaTS_User_Manual.pdf
2.) Check if your board has suffered any damage (ICs, voltages, solderpads, ...)
3.) Install a fuse
4.) Test at lower voltages or it will fry again.
5.) Try to reverse the primary coil connections. One way it should work and the other on should work less good/terrible. You have to find out by trying.
6.) Scope what you can and provide it/interpret it yourself and make some guesses

[TonyHV]

Hi, Thanks.

I am sorry I don't have a scope, and I am not fully aware how DRSSTCs work.

Yet, I guess the schematic is the same as the one in link :
http://isopack.blogspot.com/2012/05/onetesla.html

I tried reversing the primary, but no change happened at all !

Also, it might be useful that many people suggested it can be an out of tune coils, and some think it drains more current, and others think the type of solid primary coil is the problem, or something around that, and I guess it is like so since the board works fine with the LV part, i.e. I can hear the interruptions tone in the GDT.

I used 40N60 trying to copy isopack work in the link above, but I am not sure how would it help.

[Teravolt]

those chinese drivers are nock-offs losly based on the universal driver and with a ud 1.5 circuit diagram you may be able to truble shoot it. the big white capacitor is your resonant capacitor and you need it to figure out what your primary resonance is. replace the fets if damaged and se if the board funtions properly with the primary circuit at LOW power.
What levle is this for high school or college and what levle are you in beeing able to truble shoot electronics. I saw a bunch of equipment in one of your pictures can you use it. you will need a function generator, o-scope and DMM, soldering iron to fix it and the forum may be able to walk you throgh it. A DRSSTC is accualy a complicated peace of equipment with out expierience. Some guys spend many hours trying to understand it why did you want to take it on

[TonyHV]

My Idea to use DRSSTC is simply that I thoughtr DRSSTC generates bigger sparks, and it is more heavy duty to operate than SSTC.

[Mads Barnkob]

40N60 IGBTs should work as a fine replacement for the original IGBTs that you blew up.

Be sure to check all diodes, resistors etc. that is a part of the gate drive circuit. So any component from GDT to primary coil has to be checked, when there is a IGBT failure in a DRSSTC, it is common that the gate resistors, diodes or zener diodes dies aswell.

A oscilloscope is paramount necessary to trace down faults and errors on a SSTC/DRSSTC, there is simply not much idea in trying to do it without.

To learn more about how DRSSTCs work, Gao wrote some good short descriptions for his DRSSTCs: http://loneoceans.com/labs/drsstc1/ http://loneoceans.com/labs/drsstc2/ http://loneoceans.com/labs/drsstc3/

Also you should really check out my DRSSTC design guide for best practises: http://kaizerpowerelectronics.dk/tesla-coils/drsstc-design-guide/

Unfortunately is does not seem there is great success with most of the Chinese cheap drivers and products, you can find more topics discussing this on the forum if you search for "chinese".

A good stepping stone onto musical DRSSTC is to build a SSTC with a simple audio interrupter. Like a SSTC2: http://kaizerpowerelectronics.dk/tesla-coils/kaizer-sstc-ii/ with a audio interrupter: http://kaizerpowerelectronics.dk/tesla-coils/musical-sstcdrsstc-interrupter/

[TonyHV]

Hi Mads,

I was waiting impatiently to receive your reply, and I will follow your lead and check everything from GDT to the primary, and I also ordered a scope already (Jinhan JDS2023), for tracing and trouble shooting the circuit.

I also want to indicate (as for honesty) that the SSTC full bridge driver boards I also bought from China, works way beyond imagination, perfect and amazingly easy to install, with surprising results and also a good way to understand how things really work with SSTC(check my image attached).

My question to an expert like you, because I am just trying to figure out, what possibly can be the problem that first ruined my driver :
do you think an out of tune coils, can cause as much of instant damage ? or may be a low impedance primary ? or may be a long ON-time problem, due to boosting my Chinese fiber Interrupter?

I just want your first impression analysis.

thanks Mads.

[Mads Barnkob]

I think the main reason for your failure was that you did not recognize that something was wrong, before feeding it full input voltage.

This is one of the reasons why I love variacs, you can slowly ramp up the voltage and see if the current rises quickly or if its pegging or if the variac starts humming loudly, all good indicators that something is wrong if you are not getting a spark output while it does so.

at 55VAC the pulp flashes, but tiny sparks (less than 0.5 CM).
at 110VAC the pulp flashes, but little bigger sparks (1 CM) drawn by a screw driver.
at 220VAC (15 A) the board dies and a short circuit happens on the supply rails , then I have to change the IGBTs!!!

Maybe it was out of phase, you had no real control of your MOSFETs state and it could have died from cross-conduction.

Its good that you now have a working coil as you now have a basis to work out from, you know the sounds and "feeling" of a working coil, which all can seem scary for the first time builder, as most people think something is wrong when you can hear the high frequency current.

[TonyHV]

Hi Mads,

It is critical to mention that the working coil was a chinese SSTC, NOT the DRSSTC I am trying to roll. so it proves nothing but some trust in SSTC and DRSSTC drivers from China

And also I used a basic way to ramp up the voltage slowly (not variacs, but 2 cascade 220-110V transformers which gave me starting voltage of 50VAC ) and I get the short circuit feeling since my both Transformers hum very loud as I connect my driver to them, so I did that step too.

But seems like something else (apart from IGBTS is broken, so that no matter how many times I change IGBTs I still get a short circuit).

Yet my question persists, if my coils are out of tune, can this fry my IGBTs??

[Mads Barnkob]

question persists, if my coils are out of tune, can this fry my IGBTs??

Short answer, yes.

But it requires some effort. When a DRSSTC is out of tune, the energy is not transferred fully to the secondary circuit and thus the current keeps circling in the primary circuit, here you have to rely on the OCD to save your IGBTs and MMC. But does the oneTesla have OCD?

[TonyHV]

It is clearly stated in the Manual of the DRSSTC from China , that no OCD is installed, so I guess no.

Attaching below is the manual page that relates to the operation, so kindly have a look and tell me if you have any thoughts.

[Mads Barnkob]

That is one of the fundamental flaws in the oneTesla design, many people without experience buy these kits and have no knowledge of the figures mentioned about limiting on-time etc. It is a shame and I got no idea why they left out a cheap CT and comparator in a 400$ product...

[Teravolt]

one of the first things you need to do is to determin is if the primary and secondary have the same resonanant frequency. you can do this with your scope and signal generator. ebay has some signal generator kits for 7$us find a small neon light to find your fundimental resonant frequency for each. some have used back to back LEDs to find resonance but you should be able to see it on any o-scope. the chinese drivers work as advertised but usaly have ilittle information and little suport. if you have expirience with electronics then this is less of a battle. had you bought one tesla you would have there suport. what contry and sorces for semiconductors do you have?

[TonyHV]

Thanks Mads and Teravolt for the great tip,

I am waiting for my 7$ generator now and my handheld scope as we speak, yet I guess the resonance can be one issue.

I live in the middle east and I had not purchased the original oneTesla , but the chinese clone

[TonyHV]

Also are there any calculators for the ON Time?
Can the interrupter in my photo (which works perfectly for SSTC) work for my DRSSTC also ?

[pentode]

As a raw beginner to DRSSTC I hesitate to write here but is your DC bridge supply to your
DRSSRC smooth with large caps?

[TonyHV]

Yes I checked, all working fine 

[Mads Barnkob]

Also are there any calculators for the ON Time?
Can the interrupter in my photo (which works perfectly for SSTC) work for my DRSSTC also ?

You can use the MMC calculator to see the effects of adjusting on-times, BPS, etc for all the specifications of your coil: http://kaizerpowerelectronics.dk/calculators/mmc-calculator/

Your interrupter will work fine for a DRSSTC if it has something in the range of 1-500 BPS and adjustable on-time from 0-300uS

[TonyHV]

Thanks Mads, you are the king !