Output Phase Loss

What does LF mean?

This fault occurs when one of the inverter's output phases to the motor is lost, typically detected if the RMS current value for a phase drops below a detection level for 10 seconds. This indicates a potential disconnection, break in motor wiring, or a fuse blown on one phase. Operating with phase loss can lead to motor overheating, vibration, and uneven wear, severely damaging the motor.

• Loose or corroded connection at the inverter output terminals (U, V, W) or motor terminal block.
• Broken conductor in the motor cable between the inverter and the motor.
• Motor winding open circuit in one phase.
• Intermittent or failed output contactor or disconnect switch between the inverter and the motor.
• Insufficient motor load or a very light load causing current to drop below the detection threshold for an extended period (P6-01 Phase Loss Detection Level).

Click steps to track your progress.

1. 1

   Disconnect power to the inverter and confirm DC bus capacitors are discharged.

2. 2

   Visually inspect all connections at inverter output terminals (U, V, W) and motor terminals for tightness and corrosion.

3. 3

   Using a multimeter, check continuity of each motor cable phase conductor from the inverter to the motor.

4. 4

   Measure resistance of the motor windings (phase-to-phase: U-V, V-W, W-U) using an ohmmeter; values should be balanced.

5. 5

   Verify the integrity of any output contactor or disconnect switch by checking its contacts for burning or wear.

6. 6

   Adjust parameter P6-01 (Output Phase Loss Detection Level) if operating at very light loads, but ensure it remains protective.