Re: DRSSTC Field Plots

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

Hi Terry,

Did you have your "trap" in series with the primary when you blew the H 
bridge this last time.  And how did the corona ring result in the failure. 
I had discharge on my corona ring also and had to close the gap to maybe a 
1/10 inch.  Discharge disappeared then.

Gerry R


> 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