Unit was powered up successfully. There was no motor connected at Output.
As soon as the ON command (Drive Run) was given, Drive tripped with DC Link over voltage fault.
The display value of the dc link as well as the Measured Value with Meter both was rising rapidly with On command and causing trip.
There was no external reasons like Fast Decelerating, Breaking or an over voltage condition at Input.
Subsequently the repair Engineer open the drive and found one support Rod from the Body of drive was touching to the output phase .( Causing Direct short circuit of phase to Earth terminal.)
After removal of this short drive worked very well.
But the questions remain unanswered
- Why didn’t drive trip with short circuit fault.
- Why the dc link should rise if output is shorted to earth.
- What will happen if a running drive’s phase touches earth.