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.

• Motor Contactor (MC) auxiliary contact failure, preventing its state from being reported to the inverter.
• Incorrect wiring of the MC auxiliary contact feedback signal to the designated inverter digital input terminal.
• MC coil failure, preventing the contactor from closing or opening as commanded by the inverter.
• MC answer-back delay time (e.g., Parameter L7-03) set too short, causing a trip before the contactor physically responds.
• Mechanical binding or damage to the Motor Contactor itself, preventing proper operation.

Click steps to track your progress.

1. 1

   1. Verify the Motor Contactor (MC) auxiliary contact is wired correctly to the designated inverter digital input terminal as per schematic.

2. 2

   2. Measure the voltage across the MC coil terminals to confirm proper energization (e.g., 24VDC, 120VAC) when commanded.

3. 3

   3. Manually actuate the MC and use a multimeter to check for continuity across its auxiliary feedback contact to confirm operation.

4. 4

   4. Adjust the MC answer-back delay time (e.g., Parameter L7-03) to a longer value to account for mechanical contactor closure time.

5. 5

   5. Inspect the MC for any signs of mechanical damage, burnt contacts, or internal debris preventing proper operation.