50 hp 460v quantum regen drive. showed up. blown 150amp transistor fuse in drive. disassembled drive. 8 of 10 bus caps nfg. i replaced all bus caps. tested all 7 igbts. they are good. tested the 3 resistors in the drive. good. funny thing i noticed. parms in dsp went back to default. put old parameters in drive. turned on. again. lost a big drive fuse. where would you go next? im thinking of replacing dsp board, then disconnecting igbt control harness in case something is turning them on and keeping one igbt on. btw. motor and contactor are good.

The best next step to take would be going through the drive with TK’s “Universal Drive Tester” You remove the Amp Traps, power up the controller and supply the drive with 120vac through a 100 watt light bulb. Then there is a box that plugs in between the current reg & firing card and the regen board and firing cad that lets you manually fire each IGBT. It would be well worth the effort if you could get a hold of one.