Line Supply Phase Failure

What does PHF mean?

This fault indicates a loss of one or more phases in the incoming AC line supply to the drive controller, often caused by incorrect wiring, a blown input fuse, or a transient power fault. Operating a three-phase drive on a single-phase supply can also trigger this. Prolonged operation with missing phases can damage the drive's input rectifier.

• Blown input fuse on one or more phases of the incoming AC line supply.
• Loose or corroded connection on one or more input power terminals (L1, L2, L3) at the drive or upstream.
• Upstream circuit breaker tripped for one phase.
• Phase imbalance on the utility supply (e.g., significant voltage difference between phases).
• Faulty internal current sensor or voltage sensor on the drive's input side.

Click steps to track your progress.

1. 1

   1. Measure voltage between all incoming phases (L1-L2, L2-L3, L3-L1) and each phase to ground at the drive input terminals.

2. 2

   2. Check continuity of all incoming line fuses (if present) and replace any blown fuses.

3. 3

   3. Inspect all incoming power connections (L1, L2, L3) for tightness, arcing, or corrosion.

4. 4

   4. Verify that all phases are present at the upstream main disconnect or circuit breaker.

5. 5

   5. Compare individual phase currents (if displayable, e.g., using parameter P0-07 in some drives) to detect imbalance.