Undervoltage
Schneider Electric · ALTIVAR 28 Variable Speed Drive
What does USF mean?
This fault indicates that the input voltage supplied to the drive controller is too low, possibly due to a transient voltage dip, a persistent low line voltage, or a damaged internal component like a load resistor. Undervoltage can cause erratic drive behavior, loss of motor control, and potential component stress.
Complete Troubleshooting Guide
- 1
Verify the incoming line voltage at the drive's input terminals and ensure it meets the minimum requirements.
- 2
Check the configured voltage parameters in the drive controller's settings to ensure they are appropriate for the supply.
- 3
If equipped with a braking resistor, inspect it for damage as a fault within the resistor circuit could contribute to voltage anomalies.
- 4
If the fault persists after checking external factors, the drive controller may require replacement.