Motor Lost/Disconnected

What does Motor Lost mean?

This fault indicates that the variable speed drive has detected that the motor is no longer connected or that its output current has dropped below a critical threshold while the drive is commanded to run. This can be caused by a broken motor cable, a disconnected motor, or a severe motor internal fault (e.g., open winding). Operating without a motor or with a disconnected motor can lead to unstable control and potential damage to the VSD output stage, though typically less severe than a short circuit.

• Motor power cables disconnected or broken (e.g., loose terminal connections at VSD or motor, phase loss).
• Open circuit in one or more motor windings (e.g., internal break, burnt winding).
• VSD output contactor (if installed) failed in the open position or its control circuit malfunctioned.
• Incorrectly set motor minimum current threshold parameter (e.g., P1-07 for motor loss detection) causing false trips at low loads.
• Failure of the VSD's internal current sensor or its output power stage (IGBTs).

Click steps to track your progress.

1. 1

   Verify motor power cable connections at the VSD output terminals (U, V, W) and at the motor terminal box. Check torque settings.

2. 2

   Perform a continuity test on motor phases (U-V, V-W, W-U) at the motor terminal box. Measure resistance between phases (e.g., 0.1-10 Ohms for a typical motor).

3. 3

   If an output contactor is present, verify its coil voltage and contact continuity when commanded ON by the VSD.

4. 4

   Review VSD parameter P1-07 (Motor Loss Detection Current) and ensure it's set below the motor's expected no-load current but above zero.

5. 5

   Disconnect the motor cables from the VSD. Run the VSD into an inductive load bank (if available) to verify VSD output current sensing.