MC Answer-Back Fault (Contactor Feedback)

What does UV3 mean?

This fault typically indicates an issue with the feedback signal from a Motor Contactor (MC) or output contactor. If the inverter expects a contactor to close or open and does not receive the corresponding feedback signal within a set timeframe, this fault is triggered. This protects against situations where the motor may not be properly connected or disconnected, which could lead to unsafe operation.

Additional Steps

Steps 1–2 are listed in Priority Fix.

1. 3

   Verify the contactor's coil voltage and ensure it is receiving the correct command from the inverter or control system.

2. 4

   Check the inverter parameter settings related to MC answer-back delay times and polarity.

3. 5

   Replace the motor contactor or its auxiliary contact block if either is found to be faulty.