I am developing a speed control for a 3 HP compound shunt wound motor. The armature and field both require variable power control as the application requires the utilization of field weakening for short term high speeds. I built my prototype around the IXYS IGBT # IXA60IF1200NA as final drivers, it is a bit overkill but I like the packaging. I used a 800 V PRV 30 amp fast recovery diode as a snubber across the field and armature winding's.. All went well on my 1/4 HP test motor but when I tested on the application 3 HP motor the armature recovery diode shorted after 10 minutes, which, in turn, shorted my IGBT.. The PWM frequency was 88 hz as this seems to work well with larger motors.. I ususally stick to developing programs and control circuits but I got stuck with this project.. Any Ideas on a better snubber circuit????
