Retired a few years but all of the Danfoss & ABB VFD'S had built in ground fault protection. Danfoss called it earth fault when it tripped out. Probably over 90% of the Danfoss earth fault trips were false. Would make sure motor was at a compete stop then megger 480 motors with a 1,000 volt megger and restart. I'm all for ground fault protection for homes and even outdoor AC units but over 99% of the motors I wired up, trouble shoot or rep!aced were on a grounded metal plate and had copper ground wire to the motor and at my last jobs all runs from drives to motors were in steel EMT & a short section of Greenfield or sealtite with a metal core. If a motor was to ground out my thinking is it would not pose a large shock hazard. If the VFD had a bypass then an expensive three phase GFCI would be needed. I asked several drive techs how many milliamps to ground will trip out their drives but none knew. If drives have built in ground fault protection why would an expensive three phase GFCI have to be used ?
