Input Undervoltage

What does Undervoltage mean?

This fault indicates that the incoming mains supply voltage has dropped below the VSD's minimum permissible operating threshold. This can be due to a brownout, a fault in the supply network, or incorrect sizing of supply components. Sustained undervoltage can cause erratic drive operation, reduce motor torque, and potentially damage internal power components if the drive attempts to compensate. It also prevents reliable operation.

• Brownout condition on the main utility supply or plant distribution network.
• Blown fuse or tripped circuit breaker in the incoming power circuit.
• Loose or corroded connections in the input power path to the drive (L1, L2, L3).
• Incorrectly set undervoltage trip level parameter (e.g., P1-02 (Minimum DC Link Voltage)) (less common).
• Heavy load transient causing a momentary voltage dip at the drive's terminals.

Click steps to track your progress.

1. 1

   Measure incoming AC supply voltages at terminals L1, L2, L3 (phase-to-phase) using a multimeter.

2. 2

   Check all upstream fuses and circuit breakers for continuity and trip status.

3. 3

   Inspect all input power connections to the drive for tightness and signs of overheating.

4. 4

   Verify that the mains supply voltage is stable and within the drive's specified operating range (e.g., 380V +/- 10%).

5. 5

   Monitor the supply voltage with a power quality logger to identify intermittent sags or brownouts.