Input Phase Loss

What does Input Phase Loss mean?

One or more of the incoming power supply phases to the drive has been lost or experienced a significant voltage drop. This can result from issues in the upstream power grid, tripped circuit breakers, blown fuses, or loose wiring connections at the drive's input terminals. This leads to unbalanced operation and potential damage to the drive.

• Loss of one or more phases in the incoming AC power supply (e.g., L1, L2, L3 terminals) due to upstream breaker trip or utility issue.
• Loose or corroded connections on the drive's input power terminals (e.g., L1, L2, L3) or in the upstream disconnect switch.
• Blown fuse(s) in the input power circuit before the drive, leading to an unbalanced or lost phase.
• Voltage imbalance across the input phases exceeding the drive's tolerance (e.g., >5% difference).
• Drive's 'Phase Loss Detection' parameter (e.g., L2-01) is set too sensitive or is detecting a real power grid issue.

Click steps to track your progress.

1. 1

   1. Measure the incoming AC line voltage (L1-L2, L2-L3, L3-L1) at the drive's input terminals with a multimeter to confirm all phases are present and balanced (e.g., 480VAC +/- 10%).

2. 2

   2. Inspect all power wiring connections from the main breaker/disconnect to the drive's input terminals (L1, L2, L3) for tightness and signs of overheating or corrosion.

3. 3

   3. Check all upstream fuses (e.g., 3-phase fuse block) for continuity with a multimeter. Replace any blown fuses with the correct rating.

4. 4

   4. Verify that upstream circuit breakers or motor protection devices are not tripped and are sized correctly.

5. 5

   5. Adjust the 'Input Phase Loss Detection' parameter (e.g., L2-01 'Phase Loss Detection Level') if it is overly sensitive and causing nuisance trips, but ensure adequate protection.

6. 6

   6. Check for source impedance issues or transformer sizing that could cause significant voltage drop on one phase during drive operation.