Common causes include shorted drive output phase to phase, a shorted motor, locked rotor, load too heavy, accel/decel times are too short, contactor on the drive output is open or closed, motor with a FLA greater than the drive rated output current.

Corrective Action could include
Remove the motor and run the drive without the motor. If no fault, then concentrate on the motor and leads.
Check the motor for a phase to phase short. Check for a short with a 1000 v megger. A 500 v megger may not be enough to break down bad motor insulation.
Check the Drive for a phase to phase short at the output. Never use a megger on a drive. You will damage it.
Verify constants C1-01 and C1-02 are set correctly. These are the acceleration and deceleration time constants for a F7 drive.
Check the load conditions on the drive. Is the drive undersized for the load? This would happen if the inverter is replaced with another inverter that is too small for the motor.
Check the motor for locked rotor.

Common Causes that are Milnor Machine specific would be if the belts are too tight on the machine. This puts too much load on the inverter.
Is the brake dragging on the machine? Again, this increases the load to the inverter.
Are the bearings bad? Again, increases the load.

CSH 01-14-09