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ALARM 4

Mains phase loss

Danfoss · VLT HVAC Drive High Power

Hva betyr ALARM 4 ?

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.

Vanlige årsaker

  • 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).

Reparasjonssteg & Sjekkliste

Klikk på steg for å spore fremgangen.

  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.

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Verifisert teknisk data. Sist oppdatert: March 2026

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Kilde: Danfoss VLT HVAC Drive High Power