RE: Testing High voltage puck diodes. Partial failure od smiconductors in general

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Jim Mora" <jmora@xxxxxxxxxxx>

It this should happen to me I'll bite the bullet and reinstall the tube top
and  buy the 6 8020 tubes. The diode strings are way over built though, than
again, the unforeseen always becomes clear after the failure mode begins.

Jim Mora

-----Original Message-----
From: Tesla list [mailto:tesla@xxxxxxxxxx]
Sent: Wednesday, October 11, 2006 10:47 AM
To: tesla@xxxxxxxxxx
Subject: RE: Testing High voltage puck diodes. Partial failure od
smiconductors in general

Original poster: "Leigh Copp" <Leigh.Copp@xxxxxxxxxxx>

Hi Peter,

Some interesting failure modes there. I think the key difference in
power electronic application however is that the power circuit has
sufficient stored energy to assure nearly total destruction of the
device, once partial failure occurs. In large IGBT modules there are
multiple IGBT's in series and parallel. Typically one or more devices
short from Collector to Emitter, and if it is in series configuration,
this immediately places more stress on the remaining devices, so they in
turn fail in rapid succession. Once a series string is shorted, the
current from the DC bus capacitor takes care of the rest.

Cheers,

Leigh

-----Original Message-----
From: Tesla list [mailto:tesla@xxxxxxxxxx]
Sent: October 8, 2006 2:43 PM
To: tesla@xxxxxxxxxx
Subject: Re: Testing High voltage puck diodes. Partial failure

Original poster: "Peter Terren" <pterren@xxxxxxxxxxxx>

Perhaps you should look at my site where I show different modes of
LED partial failure including loss of part of the die and reduction
of reverse voltage standoff.  I am an self-proclaimed expert in LED
abuse.
http://tesladownunder.com/HighVoltage.htm#High%20speed%20Tesla%20spark%2
0photography%20-%20LED%20polarity,%20current%20indicator

Peter


 >Original poster: "Leigh Copp" <Leigh.Copp@xxxxxxxxxxx>
 >Hi Jim,
 >In the last 20 years I've heard a lot of talk about diodes (and
 >other devices) failing intermittently. I have yet however, to ever
 >see a semiconductor that was anything in between good, and bad. They
 >either fail from too much voltage, or too much current, or too much
heat. ....
 >I am open to the benefit of  experience from others, but I have
 >spent literally hundreds of hours in the field investigating claims
 >of power semiconductors that would intermittently fail, or only fail
 >at high current or voltage. I can definitively say that I have yet
 >to ever fail to find other problems that were directly responsible.
 >... So for my 2.5 cents worth check them with a multimeter, and then
 >install them.
 >Cheers,
 >Leigh