Undervoltage

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.

Additional Steps

Steps 1–2 are listed in Priority Fix.

1. 3

   If equipped with a braking resistor, inspect it for damage as a fault within the resistor circuit could contribute to voltage anomalies.

2. 4

   If the fault persists after checking external factors, the drive controller may require replacement.