Cause : Safe motor temperature 1 comes when the thermistor protection module installed in slot 1 indicates overtemperature.

The fault code 4991 in your ABB ACS880 drive indicates a safe motor temperature fault. This means the drive has detected a potential overheating condition in the motor.

1. Check the cooling of the motor.
2. Check the motor load and drive ratings.
3. Check the wiring of the temperature sensor.
4. Repair wiring if faulty.
5. Measure the resistance of the sensor.
6. Replace sensor if faulty.