Input Phase Failure

What does -PHF mean?

This fault indicates a loss or significant imbalance of one or more input phases to the drive controller. Common causes include blown line fuses, loose connections, or an issue with the utility supply. Using a 3-phase drive on a single-phase supply without proper configuration can also trigger this. Operating with missing phases can lead to motor and drive damage due to unbalanced currents.

• Blown input line fuse (L1, L2, or L3) or tripped input circuit breaker feeding the drive.
• Loose electrical connection at the main contactor, isolator switch, or drive input terminals (R, S, T).
• Utility power supply issue (e.g., loss of a phase from the electrical grid or distribution panel).
• Significant voltage imbalance (e.g., >3%) between input phases, causing the drive to detect a missing phase.
• Drive internal input rectifier bridge fault (less common, but possible if one leg fails to conduct).

Click steps to track your progress.

1. 1

   Measure voltage across all three input phases (L1-L2, L2-L3, L3-L1) at the drive's input terminals (R, S, T) using a multimeter.

2. 2

   Check continuity of all input line fuses with a multimeter (power OFF, lockout/tagout).

3. 3

   Inspect and tighten all connections from the main power supply to the drive input terminals (R, S, T) and associated protective devices.

4. 4

   Verify the input power source by measuring voltages at the supply side of the main breaker or fuse block.

5. 5

   If input voltages are balanced and fuses are good, internal rectifier issue may be present; contact drive vendor for further diagnosis.