Yet another OneTesla w/o kit

Non-kit projects based on the public Gen1 designs

Re: Yet another OneTesla w/o kit

Postby Bayley » Thu Nov 21, 2013 8:56 pm

bomber315 wrote:that last picture makes me wonder if there is a socket of some sorts that the igbt's could simply plug into on the board. sorry guys im am really new to this "build your own board" world

it would be cool to use a socket for the igbt's tho, i plan on blowing a few.... handfuls haha


I used to use 2mm pitch Phoenix connectors for this, but it'll require some hacking to get the terminals to work on the board. There aren't any "official" TO-247 sockets, at least that I know of.
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Re: Yet another OneTesla w/o kit

Postby Frost273 » Sat Nov 30, 2013 2:31 pm

Finally got my new IGBTs today. Mounted them on separate heatsinks as planned. (I'll make some photos soon).

My problem is that the sparks are small.
And they are distinct only in the darkness. I can go a bit more then half of power on an interrupter. The IGBTs are cold. Sparks grow up to 3-4 cm when I move fluorescent lamp closer but that's the maximum I get.

Is this due to poor tuning?
Or can it be because of rectifying bridge usage (KBPC3510) not a bridge on fast mur460 diodes?
My counted frequencies are approximately 230 kHz for the secondary and 218 kHz for the primary with 8 turns.

Please help to understand what I did wrong.

No oscilloscope I can access for now.
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Re: Yet another OneTesla w/o kit

Postby Frost273 » Thu Dec 05, 2013 3:36 pm

I have completed 555 Tesla Coil Tuner (honestly I cannot say how accurate it is) and it shows that my secondary's frequency is more then 400 kHz. When I add one more toroid to the topload the performance seams to be better. But when I add even more capacitance it goes worse again.


>? Can it be true? Or can it be due to higher active resistance of my secondary coil (around 560 Ohm).

Also here is my setup of the IGBT bridge:



One more question:
Can optical transmitter cause bad performance if it's output is not as bright as it meant to be?
I used IF-E91A instead of IF-E96. What do you think?
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Last edited by Frost273 on Sun Mar 02, 2014 3:32 pm, edited 1 time in total.
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Re: Yet another OneTesla w/o kit

Postby Bayley » Thu Dec 05, 2013 5:42 pm

Your IGBT setup will perform extremely poorly; those long thin wires add loads of parasitic inductance which translates into spikes during switching (V=L*dI/dt).
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Re: Yet another OneTesla w/o kit

Postby DJKOR » Thu Dec 05, 2013 9:47 pm

Did you rely solely on the scale of that printout or have you compared it with a frequency counter/meter?
Image
My build thread: viewtopic.php?f=15&t=998 | 246kHz Primary / 267kHz Secondary
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Re: Yet another OneTesla w/o kit

Postby loneoceans » Fri Dec 06, 2013 12:36 am

Frost273 wrote:Finally got my new IGBTs today. Mounted them on separate heatsinks as planned. (I'll make some photos soon).

My problem is that the sparks are small.
And they are distinct only in the darkness. I can go a bit more then half of power on an interrupter. The IGBTs are cold. Sparks grow up to 3-4 cm when I move fluorescent lamp closer but that's the maximum I get.

Is this due to poor tuning?
Or can it be because of rectifying bridge usage (KBPC3510) not a bridge on fast mur460 diodes?
My counted frequencies are approximately 230 kHz for the secondary and 218 kHz for the primary with 8 turns.

Please help to understand what I did wrong.

No oscilloscope I can access for now.



What sort of specs are your secondary and primary? Where did you get the figures of 230 and 218kHz from? As DJKOR suggested, it would be great to try to find an oscilloscope somewhere to find the true resonant frequencies. In my opinion, 8 turns is too much for the primary and will cause severe flash-overs due to the very high coupling.

Also, Bayley is right, the long you have for the IGBTs are probably a bad idea. The oneTesla board was designed to be low-inductance. Your current setup will see big spikes across the IGBTs which might kill them quickly. Finally, the bridge rectifier you use will work fine. Just make sure you wired them up the right way.
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Re: Yet another OneTesla w/o kit

Postby Frost273 » Sat Dec 07, 2013 8:52 am

Thank you for the replies!

I completely devoted Friday to follow your advices and redid what I have done.
Bayley, you were totally right about the way long leads impact the IGBT's performance. Never going to make the same mistake.

DJKOR, yeap. I relied on the scale guy who designed this board provided. I guess (I'm sure) it doesn't represent the real frequency, but the position of a tuning knob was pointing on the same spot both for the primary and secondary circuits. This encouraged me a bit, so I went onto power testing.

I didn't reject the idea of placing transistors on separate heatsinks and installed pair of 1.5ke220 as well.

Some photos of the monstrous setup:
Image

and from the other side
Image

You might want to check it's performance.
The power is somewhere from 1/4 to 1/3 of the scale, maybe a bit more, but don't think I had reached the half of it.
Youtube - Drunkensailor
First video
La Bamba
Lemon Tree
Fixed frequency
Filmed on phone camera, please don't judge me.


Hi loneoceans! ;)
Thank you for keeping your eye on my progress!

The parameters of the primary are:
Coil diameter: 90mm; capacitance: 0.0662 uF; 8 turns; something between 13 and 14 AWG with total lead length of 50 cm.

Parameters of the secondary:
Coil diameter: 63 mm; AWG 35; 2020±20 turns.
Topload looks like this with 7 cm inner and 19 cm outer diameters.
Image
I'll be grateful if you recheck my calculations, in case I have made a mistake.




It's good I've made the second oneTesla main board, so I can evade my previous mistakes at it.
It's not finished, I've damaged my optical receiver. Have to wait again. I already got used to :)
Image
Image

Also with suppressors onboard.
Image
Image
Last edited by Frost273 on Mon Dec 09, 2013 4:05 am, edited 1 time in total.
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Re: Yet another OneTesla w/o kit

Postby Frost273 » Mon Dec 09, 2013 3:16 am

I tried to run my OneTesla with the secondary coil I had made at first (with 1800 turns) and I got some flashovers.
The question is can I use duct tape instead of revarnishing with polyurethane?
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Re: Yet another OneTesla w/o kit

Postby Alex » Mon Dec 09, 2013 6:14 am

I think duct tape is slightly conductive...
You can get away with wrapping some clear packing tape around it though but be warned the tape can hold some static charge afterwards (you could get a shock from touching the secondary)
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Re: Yet another OneTesla w/o kit

Postby ican » Fri Dec 13, 2013 1:17 pm

Don't use packing tape or Duct tape, use Kapton tape instead... It's expensive, but completely insulative, and will work just as well as a revarnish of your secondary.
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