UNDERVOLTAGE
Schneider Electric · ATV32HD11N4 Variable Speed Drive
What does USF mean?
This fault indicates an insufficient incoming line supply voltage, a transient voltage dip, or a potential issue with the drive's internal precharge resistor. If the voltage drops below the drive's operational threshold, it will be unable to operate reliably or at all, causing unexpected shutdowns and potential component stress. Sustained undervoltage can prevent motor start-up or lead to erratic performance.
Additional Steps
Steps 1–2 are listed in Priority Fix.
- 3
If transient voltage dips are suspected, monitor the line voltage with a power quality analyzer. Consider using a line choke or UPS for stability.
- 4
If internal components (like a damaged precharge resistor) are suspected after ruling out external power issues, the drive may require replacement or professional service.