Kaizer DRSSTC II

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

Introduction

I wanted to build a small DRSSTC in a few days without having prepared anything, most parts are reused or scrapped from things I have found and saved.

Considerations

I was nervous that the metal enclosure for the driver was too close to the primary coil and would absorb some of the energy, first tests show no sign of heating of the metal.

I made the bridge section entirely on a normal one sided PCB and was not too sure if the traces were thick enough to withstand the high peak currents or keep a low inductance layout. It all seems to work without problems.

Specifications

	Revision 1	Revision 2
Bridge	2x G12N60C3D IGBTs in a half bridge configuration	2x IXGN60N60C2D1 IGBTs in a half bridge configuration
Bridge supply	0 – 160VAC through a variac, 6A rectifier bridge and 2x Aerovox 410uF 430V filtering capacitors in parallel.	0 – 210VAC
Primary coil	Flat primary. Inner diameter 70 mm, Outer diameter 187,36 mm. 6 turns 1,78 mm copper wire (2,5 mm²), turn spacing 8 mm. Tapped at 4.8 turns.
MMC	2 in series Cornell Dubilier (CDE) 942C20P15K-F capacitors for 0.075uF at 4000VDC rating.
Secondary coil	50 mm diameter, 200 mm long, 1430 windings, 0,127 mm enamelled copper wire.
Resonant frequency	Around 327 kHz.
Topload	40 x 215 mm aluminium tape on a Styrofoam toroid.
Input power	250BPS, 250uS ontime, 68 primary cycles, 300A limiter: 120VAC in.	350BPS, 120uS ontime, 35 primary cycles, 280A limiter: 210 VAC in at 2A. 420 Watt.
Spark length	Up to 240 mm long sparks.	Up to 370 mm long sparks.

Schematic

The driver is a variation of Steve Wards universal driver and beneath you can see the bridge schematics.

 

Construction

13th August 2011
Optimize driver PCB, design bridge PCB, toner transfer to PCB.

14th August 2011
Etch PCBs, assemble bridge PCB completely, half done with driver assembly. Heat sinks, electrolytic capacitors, voltage splitting capacitors and rectifier bridge are all salvaged components. Materials for building a enclosure and base is found. Lexan salvaged from LCD monitors is used for the base and some normal house wiring is used for the primary coil.

 

15th August 2011
Winding CTs for feedback and OCD, building enclosure and base, driver PCB assembled.

 

16th August 2011
Driver PCB fault finding and testing, enclosure and base building. I had forgot to add the trace that resets the OCD on the driver board after I moved it while optimizing the board layout.

 

17th August 2011
Complete construction and ran first test, no first light.

 

28th August 2011
First light, phasing of feedback transformer was wrong.

3rd September 2011
24 cm sparks, running 250uS, 68 primary cycles, 120VAC in, 268A primary current. 250BPS.

 

Here is a scope shot of the primary current waveform and a zoom of the same.

 

4th September 2011

I blew up both IGBT transistors running at the same settings as above on the 3rd September 2011, but at 160VAC input, nothing violent, just a flash and all was silent.

I will rebuild the bridge with IXYS IXGN60N60C2D1 IGBTs, which will hopefully make the bridge indestructible compared to the size of this Tesla coil.

11th September 2011

Rebuild the bridge and spent the day fault finding on the circuits as it did not work, turned out to be a 33V zener diode on the bridge board that was short circuited.

 

16th September 2011

I recorded some data from different settings and came up with following before admitting that my heat sink is just too small. Further tuning is till needed, I hope it can do better and it seems to never go higher than 280A primary current.

I peak	Voltage in, AC	Current in, AC	Burst length	BPS	Watt, AC	Spark length, mm
280	210	0,5	120	200	105	274
280	210	0,75	120	300	157,5	290
280	210	2	120	350	420	354
280	210	4	120	500	840	370

200 BPS, 274 mm sparks.

 

350 BPS, 354 mm sparks.

 

500 BPS, 370 mm sparks.

 

Here is the current waveform which pretty much stayed the same doing these tests, also a better quality picture of the sparks.

 

Additional tuning gave me much better results in the form of almost the same spark output at lower on time, lower peak current and lower power in.

Here it is a screenshot of a spark going out to 337 mm running 70uS ontime, 260A peak current, 300 – 400 BPS at 260VAC at 0.5A.

 

Conclusion

Revision 1

It is no problem building a small DRSSTC in a few days with some previous knowledge and a off the shelf secondary coil.

In the future I will properly not make another Tesla coil with TO-247 IGBTs, I need some more overhead with the way I push my Tesla coils.

Demonstration

28th August 2011

First light

 

3rd September 2011

Came out a bit dark, but shows 24 cm sparks, running 250uS, 68 primary cycles, 120VAC in, 268A primary current. 250BPS.

 

16th September 2011

37 cm sparks, running 120uS, 35 primary cycles, 210VAC in, 280A primary current. 200 – 400 BPS.

 

16th September 2011

33,7 cm sparks, running 70uS, 260VAC in, 260A primary current. 300 – 400 BPS.

14th February 2012

Playing Doom 1 – Episode 1 soundtrack with my new midi modulator.