Cause : Excess temperature comes when the drive power unit module temperature is excessive, it means that the temperature within the drive has reached levels that are higher than the safe operating limits. 

The A4B0 warning in your ABB ACS560 drive indicates an excess temperature warning. This means the internal temperature within the drive has exceeded the pre-set warning limit.

1. Check ambient conditions.
2. Check air flow and fan operation.
3. Check heatsink fins for dust pick-up.
4. Check motor power against drive power.