At 21.00 2011.12.28, you wrote:
>At 07:13 AM 12/28/2011, Electron wrote:
>
>>For this prototype, I had soldered the driver output pin directly on the
>>gate of the IGBT, and *this* caused the oscillations!!
>
>Yep!
>
>This catches a LOT of people who haven't dealt with fast FETs or=20
>IGBTs previously.  It certainly got me when I first dealt with such things=
..
>
>I generally use a low-value resistor (10R-47R), depending on the=20
>amount of gate capacitance.  But I think that your idea of using a=20
>ferrite bead is better.
>
>One of my co-workers was working with some high-power stuff many=20
>years ago and misunderstood my instructions when I told him to=20
>install 47R resistors as close to the FET gate as possible - he had=20
>long, meandering wires (6") that went from the FETs on the heatsink=20
>back to his driver board.  What he did instead was to put the=20
>resistors at the driver board.
>
>The FETs oscillated and self-destructed several times before he asked=20
>me for help.  Simply moving the gate resistors back to right beside=20
>the FETs (where they should have been) fixed the problem.

An example of when simulators are deceiving. ;)


>The FETs were driving large wire-wound heating elements (800V, 30A)=20
>and those heating elements were inductive as hell.

I don't wanna imagine. Not after today's debugging session. Tomorrow. :D


>dwayne
>
>--=20
>Dwayne Reid   <dwayner@planet.eon.net>
>Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
>(780) 489-3199 voice          (780) 487-6397 fax
>www.trinity-electronics.com
>Custom Electronics Design and Manufacturing
>
>--=20
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