Im in the process of trying to upgrade a 2 hp AC drive to 90 hp. Im doing this by using bigger external IGBTs.
I'm making progress. The IGBT's I have won't be easy to integrate, but I have been learning.
Here is what the firing signal looks like. This is a PWM version of the top half of a sine wave being fed into the drives IGBT Pack
Zoomed in it looks like a square wave with varying width pulses. This is with no IGBT connected, the voltage increased from 14v to 18v because the load was removed.
Here I have my external "big" IGBT connected, and the firing circuit falls on its face, only 5v pk-to-pk.
I think I have sourced some IGBT's with less trigger current requirements, and hope to have my motor turning soon! Checking to see if anyone has and free advice they'd like to share =)
Here is the IGBT I took out.