Coil working

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Coil working

Postby LenShustek » Thu Apr 10, 2014 2:00 pm

My coil is now working moderately well (about 18" arcs) and playing polyphonic music. See the movie at http://www.shustek.com/teslacoil/OneTesla_10Apr2014.wmv and the attached photo.

At first I had a wimpy arc and blew the IGBTs. My secondary is 240 ohms and resonates with a signal generator at 293 KHz. The primary was 6 turns and resonated at 254 KHz, which was too low. And at moderate power they seemed to be way too far apart: 312 KHz and 238 KHz, respectively. So I raised the primary resonant frequency by changing to 5 turns, and the result is what you see. I can run at max power with no ill effects. I suspect some fine-tuning (changing the primary capacitor or using partial turns on the coil) could make the arcs even better.

This is a nice and remarkably simple design! I'm working on a coil twice as large, using more more complicated circuitry and 75-amp IGBTs driving a primary made from 1/4" copper tubing. But I keep blowing the IGBTs there too. Now that I see how critical matching the primary and secondary resonance is, I might be able to get that one running.

-- Len

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Re: Coil working

Postby Alex » Fri Apr 11, 2014 3:40 pm

pictures of the bigger coil? (:
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Re: Coil working

Postby LenShustek » Fri Apr 11, 2014 4:55 pm

Below is a bad photo of my bigger coil. You can also see some videos (before the expensive IGBTs blew!) at
http://www.shustek.com/teslacoil/tesla_20Nov2011_01.wmv and
http://www.shustek.com/teslacoil/tesla_7Dec2011_03.wmv

It started off based on Dan McCauley's "miniBrute" design (http://www.easternvoltageresearch.com/), but then I completely redesigned the IGBT circuits using Avago ACPL-P343 gate drivers and dual independent floating supplies. It's a nice design that doesn't work....yet. It was while I was pondering that I decided to build the oneTesla version.

-- Len

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