To test an IGBT with Multimeter , the meter should be used in diode-checking mode. It should have battery voltage of less than 20V (a typical unit using 9V battery is alright).
To test collector-emitter junction:
- With the module out of circuit, remove the conductive foam and short the gate to the emitter.
- With multimeter in diode-check mode, the collector to emitter should give a normal diode reading with positive on the emitter and negative on the collector.
- The multimeter should read open or infinite with positive on the collector and negative on the emitter. Damages IGBTs may test as shorted in both positive and negative directions, open in both directions , or resistive in both directions.
For gate oxide test : With multimeter in resistance mode, the resistance from gate to collector and gate to emitter should be infinite on a good device. A damaged device may appear shorted or have resistance leakage from gate to collector and/or emitter.