IGBT Limitations

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Greg Leyh by way of Terry Fritz <twftesla-at-qwest-dot-net>" <lod-at-pacbell-dot-net>

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>Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

[snip]

>In other news... I designed in IGBT current tester. Here is the simple
>diagram:
>http://hot-streamer-dot-com/temp/OLTC08-28-06.gif
>Here is the messy one:
>http://hot-streamer-dot-com/temp/OLTC08-28-07.gif
>It is basically a copy of a single section of the coil. I played the
>values to get an almost perfect matching current waveform to the real one
>but I can push 600 peak amps here on a single IGBT (1200 amps with a slight
>modification!). I will probably use the coil's drive modules to run it but
>making another drive circuit is pretty easy too. With this tester I can
>run the IGBTs until they break and determine how hard I can push them.
>apparently nobody knows how hard IGBTs can be pushed in such case. Be
>interesting to see :-))


IGBTs, like many power bipolar technologies, can be reliably
operated in a pulsed-mode at many times their rated DC current.
Some manufacturers will offer an I^2*t rating for their devices,
which implies that the device can safely run at twice the current
for one-fourth the time.  Other manufacturers will specify a 1mS
repetitive pulsed-current rating.  An IGBT that I'm currently
using at work has a 1mS rating of 1600A repetitive, at 6,5ooV.
In a pulsed-power application this IGBT can continuously produce
3,oooA, 3uS pulses at 120 PPS.

Recently I was offered the task of figuring out why these IGBTs
fail catastrophically during output fault events.  Everyone else
in the group was too buried in their projects, so I begrudgingly
accepted.  <emote>

If you wish the gory details of an IGBT autopsy, you can view
them here:

http://www-group.slac.stanford.edu/esd/index.html


-GL



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