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RE: DRSSTC goes BOOM!!! :o(



Original poster: "jimmy hynes by way of Terry Fritz <teslalist-at-qwest-dot-net>" <chunkyboy86-at-yahoo-dot-com>

Hi Steve,

You're right, and I feel really stupid for not figuring it out. I am not 
using a heatsink, so I was careful to monitor the case temp with a 
thermocouple. It only rose from 75 to 95 degrees F. I didn't think about 
the thermal capacitance of the case, and that it was only heating for 100us 
every 100ms with a time constant of several seconds.

At lower voltage the temperature increase was way less than proportional to 
the 20 degrees at full voltage. When I was debugging some other problems, I 
noticed that the primary voltage would only grow for a few cycles, then it 
would remain at the same level. I had assumed it was caused by other 
problems. I measured it again while it was running. This time I thought 
that the high electic field, magnetic field, and ground loops could have 
been messing it up. In hindsight,  I had a ton of evidence and I should 
have figured it out before it blew.

Now I just have to figure out why the things can't take any current! Could 
you tell from the picture if it was one big die, or a bunch in parallel? I 
haven't done any current measurements yet, but I figured if the 40 amp IGBT 
could take ~1000 amps if you really push it, then a 150 amp one would be 
able to do it no problem. I was thinking of doing a test setup similar to 
yours for testing the IGBT brick, and to sense currnet I would use a piece 
of twisted 30 gauge wirewrapping wire, and calculate the resistance based 
on the measured copper diameter. Did you ever find out how much current 
your bricks could take?

By the way, it did actually blow up. Parts of it went flying across the 
garage. In order for that to happen, something must have vaporized.

Thanks,

Jimmy

Tesla list <tesla-at-pupman-dot-com> wrote:
Original poster: "Steve Conner by way of Terry Fritz "



-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: 09 July 2003 00:56
To: tesla-at-pupman-dot-com
Subject: DRSSTC goes BOOM!!! :o(

 >the sparks didn't seem
 >to grow much from 60 to 120 volts.

Didn't that set some alarm bells ringing? If it was working properly, they
should have doubled in length. What _I_ think may have happened is that you
ran out of transconductance at 60 volts, so the primary current stopped
growing, and all the extra power after that went to heating the IGBTs,
hence, boom!

 >I turned it up to 30
 >volts to make sure everything was working, and then cranked it up the rest
 >of the way. BOOM!!!

:( Did the case of the IGBT actually burst open by itself o! r did you break
it open for examination? And where's the silicon? I can't actually see any
in there! Maybe it all vaporised :-0 Worse luck but don't give up now, it
sounds like you're nearly there

Steve C.