Kaizer Power Electronics

Kaizer SSTC I

WARNING!: Working with electricity is dangerous, all information found on my site is for educational purpose and I accept no responsibility for others actions using the information found on this site.

Read this document about safety! http://www.pupman.com/safety.htm

Introduction

This is my first solid state Tesla coil, so I went with a sturdy and proven schematic made by Steve Ward. A lot of other coilers have replicated this circuit with great success and therefore it is easy to find information how it works and how to troubleshoot it.

Considerations

One of the differences from the original circuit is that I use 230VAC input instead of 115VAC. So capacitors and MOSFETs have a higher voltage rating.

The interrupter will be changed to go down to a very low break rate.

Specifications

Schematic

Construction

22nd January 2009

I began the construction of the half bridge circuit in a small plastic box, the heatsinks are a Pentium II heatsink cut in half. The bridge is made fra copper wire size 2.5mm² / AWG14.

The bridge is made from a 8A bridge rectifier with 330uF 450V smoothing capacitor, two IRFP460 mosfets with MUR1560 diodes, two 0.68 uF 400VAC film capacitors for the voltage splitter and 10R gate resistors.

The driver circuit is made on veroboard with a external 12VDC powersupply.

Troubleshooting

23. january 2009

When I first tried to run the driver circuit separately to test the driver before connecting it to the MOSFETs, it only resulted in the MOSFET driver chips (UCC37321/UCC37322) catching fire and burning up like a small volcano. This did ofcourse upset me when it happend once more when I had changed the chips. This led me to seek help and I learned that running the driver chips unloaded, without a MOSFET or GDT connected to the outputs, the chips will oscillate into oblivion and burn themself down.

With the complete circuit put together it all worked except the primary coil was phased wrong, but it was no problem since I used bananaplugs for the primary connections.

I ran the coil as CW (Continues Wave, non interrupted so its switching at its resonant frequency) to stress it to its maximum, which also did result in failures at 230VAC in, drawing around 4 to 5A.

The secondary coil was grounded to the mains ground in my house, but by accident I were using a plug without a earth connection in, so the secondary earth was arcing to the phase and neutral in my powerbar. Pushing around 1 kW into this rather small circuit with passive cooling became enough combined with HF noise on the phase and neutral and one of the MOSFETs exploded violently and the other died silently. Here I discovered my design did not make it easy to change the MOSFETs, a important thing to consider in future constructions.

For the next couple of days I could not get the coil to work again. Everything in the driver circuit was changed and measured with a oscilloscope without finding anything out of order. It was first when I by accident measured shortcircuit connections with a DMM that I discovered one of the secondary windings on the GDT was not connected to the MOSFET, it was because the gate resistor was destroyed from the shortcircuit of the MOSFETs. Changing the 10R resistor made the whole thing work like a charm again.

Sparks

Here are some pictures from the first light, input power is from 30VAC to 230VAC at up to 5A.

Conclusion

Building this clone of Steve Wards SSTC5 was a great introduction to solid state tesla coils, I now have a understanding of how it works from interuptor to driver to bridge.

Further projects with this circuit will be a complete rebuild with audio modulator and a full bridge of MOSFETs, this will be a separate project.

Posted October 22, 2009 by Mads Barnkob | Log in