Mains phase loss

What does ALARM 4 mean?

A phase is missing on the supply side, or the mains voltage imbalance is too high. This message also appears for a fault in the input rectifier. Options for handling this are programmed in parameter 14-12 Function at Mains Imbalance. Operating with a missing phase can severely damage the motor or the frequency converter.

• One or more phases of the incoming AC mains supply are missing due to a tripped breaker, blown fuse, or utility fault.
• Significant voltage imbalance (e.g., >2%) between phases on the mains supply.
• Faulty or damaged input rectifier bridge within the frequency converter.
• Loose or corroded connections on the input terminals (L1, L2, L3) of the frequency converter.
• Incorrect setting of parameter P1-80 (Mains Phase Monitoring Function) or P1-81 (Mains Phase Imbalance).

Click steps to track your progress.

1. 1

   Measure the voltage between all incoming phases (L1-L2, L2-L3, L3-L1) at the frequency converter's input terminals using a multimeter.

2. 2

   Check for continuity of all fuses and trip status of all circuit breakers upstream of the frequency converter.

3. 3

   Inspect mains input wiring for loose connections or corrosion at the frequency converter's L1, L2, L3 terminals.

4. 4

   Verify parameter P1-80 (Mains Phase Monitoring Function) and P1-81 (Mains Phase Imbalance) settings are appropriate for the application.

5. 5

   Isolate the frequency converter and perform a diode test on the input rectifier bridge (if accessible and safe) to check for shorted or open diodes.