Spare drives sitting on your shelf longer than a year may need to have the caps reformed.

The capacitors need to be reformed (re-aged) if the drive has been non-operational for more than one year. The longer a VFD sits without external power, the more rigorous the reforming of the capacitors. 

For 220-230V and 380-480V models apply supply voltage of approximately 220Vac, three-phase or single-phase input, 50 or 60 Hz, without connecting a motor to the output. This voltage should be applied for a period of 1 hour. After this energizing process, a wait period of 24 hours before installing or utilizing the drive for motor control is vital. Part of the oxide insulation is formed during this “resting” period. For 500-600V, 500-690V and 660-690V models use the same procedure applying a voltage between 300 and 330Vac to the inverter input.