DRSSTC Field Plots

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Terry Fritz <teslalist@xxxxxxxxxxxxxxxxxxxxxxx>

Hi,

I was having trouble with the corona ring on the top of the secondary of my 
DRSSTC breaking out and arcing over.  So I finally got around to making a 
field plot:

http://hot-streamer.com/temp/drsstc-a-old.gif

Obviously, the corona ring is a serious stress point!!

So I fiddled with it and I am going to remove the ring completely and lower 
the top terminal 2 inches.  Then it looks like this:

http://hot-streamer.com/temp/drsstc-a-new.gif

It also has a nicer HV field shape now:

http://hot-streamer.com/temp/drsstc-a-10.gif

I just ran it though E-Tesla and plotted it with Mathcad6 (I see the color 
picture shows a Mathcad plotting bug..).

Hopefully this will fix the arc overs and I won't have to replace the IGBTs 
again.  I blew all the silicon on the bridge last time.  I blew 1/2 of it, 
but just kept running it as a 1/2 bridge ;-)))  I took out all the 
protection TVSs across the gates and everything, but nothing else was 
damaged.  I really like the optical gate drive.  So far it seems to work 
perfectly and has never broken even if the load is all fried.

The new beefed up H-bridge also seems to be immune to blowing traces off 
now to ;-))

I guess the protectors are not the final answer to blowing IGBTs since they 
were always in place.  Just have to avoid arcing the to primary...

Cheers,

	Terry