What would cause unit to display short circuit fault on ATV66 drives with bypass?
Check for possible short circuits or ground faults in the motor or motor leads.
Go into menu 7.4 and disable output phase loss and then go to next step of powering unit up with no motor connected. If fault clears then suspect issue is external but would want to go one step further to confirm.
Run drive with no motor disconnected at 15, 30, 45 and 60 Hz. Measure output phase to phase voltages. They should be balanced within a few volts.
If all this ok, look further at output wiring and motor.
If megger the motor be sure to use at least 1000v megger.
If unit has an Iso/Bypass arrangement, there may be problems on the output of the drive.
Check for loose connections on the drive output, at the motor and at the isolation/bypass contactors and overload relay.
Additionally, common areas of wear on the contactor include broken or cracked contact carrier, debris in the contactor causing loss of freedom of movement, or welded contact(s).
For 185 and 225 ampere devices, the movable contacts may have been overtightened during manufacturing. This was only reported as a POSSIBLE issue on devices with the manufacturing date code of 0118 through and including 0146 (or April 29th through December 1st, 2001). Refer to notification letter sent out for details on problem, products affected, and how to check.