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Registered Member #1034
Joined: Sat Sept 29 2007, 12:50PM
Location: Chillicothe, Ohio
Posts: 154
Last summer Bud Mohrman gave me a DRSSTC driver controller of the type thats on Steve Wards web site and with that and a little advice I finely got around to building a full bridge DRSSTC. I will list all the specs and post pictures here. Maybe some of you can make suggestions because I know this thing could be a better performer. At 220 volts input I can get 23 inch sparks but when I run the voltage that high the IGBTs blow up frequently. In the pictures it is running at about 160 volts input and getting 12 inch sparks. One thing I know I did poorly was in keeping the electrical connections in the bridge circuit as short as possible. Here are some specs.
Resonant frequency 70 khz, Primary capacitor .1uf at 10kv Primary turns 10
IGBT s G40N60B3 with external flywheel diodes
Interrupt rate 260 Bps On time 100us (use signal generator as interrupter)
Registered Member #2161
Joined: Fri Jun 05 2009, 03:36PM
Location:
Posts: 247
Hi Roger,
It has been a while since I had a running DRSSTC, but I seem to remember that playing around with the coupling made a noticeable difference in performance.
It is hard to tell, but from the looks of it, it seems as though your coupling is on the low side? I would also look at playing with the on time and interrupt rates.
However, I believe you likely have some ringing and other issues due to your bridge cooling setup (great use of those old CPU coolers :), it would cool great in a SSTC setup, however it is likely causing issue due to the much higher switching currents. I think you would help your reliability considerably, if you can get those IGBT's close together.
Here is an old video of mine, it used a slow Gen 1. IGBT, I was able to push the spark and amperage by running longer on-times and with a pretty high coupling. However, this was one of those half-bridhe bricks so the leads were minimized from the factory.
Regards, Rok
PS: Still remember your great VTTC from youtube, and it has been years. :)
Registered Member #1034
Joined: Sat Sept 29 2007, 12:50PM
Location: Chillicothe, Ohio
Posts: 154
Thanks for the suggestions. In planing to build a new driver soon. The heat sinks I am using now are definitely an overkill as they don't even get warm when the coil is running so I'm going to work on getting everything closer together.
Registered Member #2989
Joined: Sun Jul 11 2010, 12:01AM
Location: UK
Posts: 94
ISOPLUS247 IGBTs are quite handy as you can mount them on the same heatsink say two of them using gull wing clips.
here's some thoughts if you use a very sharp break out point it will only come from there and the streamers will be shorter, maybe try a small round bit on the end of it. are you sure you have it tuned well having anything like that ball above will easily put it out of tune if not set up/tuned with it in place? the lower end of the secondary is it on a good ground? protection diodes on the IGBTs gate? could your sig gen signal be getting messed with you have some long leads there you may find there is a lot of noise getting back into the mains wiring, filters?
anyway hope some of this mad rambling may throw up some ideas
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My First DRSSTC
