RE: IGBT Brick hits 1200A

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

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

Original poster: "Stephen Conner" <steve-at-scopeboy-dot-com>

>I hooked up a test circuit for the bricks using a 10" single turn coil and 
>three 0.94uF MO caps in parallel. I charged the MO caps to 600V and then 
>turned the IGBT on briefly. These are the waveforms I got:
>
>http://www.scopeboy-dot-com/tesla/oltc2/bricktestwfm.jpg
>
>The current is about 1200A peak, that is still within the manufacturers 
>ratings :( Once I get a higher voltage supply I can get it up to about 
>2000A. You can see that the losses are quite high but much of this is 
>probably due to the dodgy oven caps and the 0.025 ohm current shunt. Also 
>check out the massive ringing due to recovery of the flywheel diode.


The ringing appears to be caused by the fact that the IGBT
is trying to turn off during the haversine when the IGBT elements
are conducting current.  I would think that turning the IGBT off
about 2uS earlier [during the diode haversine] would accomplish
smoother commutation.