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.

Complete Troubleshooting Guide

1. 1

   Inspect the wiring for the motor contactor's auxiliary contacts (feedback circuit) to the inverter's input terminals.

2. 2

   Manually actuate the motor contactor (with power off) to check its mechanical operation and contact continuity.

3. 3

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

4. 4

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

5. 5

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