DC Bus Undervoltage

What does Uv1 mean?

This fault occurs when the DC bus voltage drops below a critical detection level, which is approximately 190V for 200V class drives and 380V for 400V class drives (or 350V when E1-01 < 400V). Common causes include phase loss in the input power, loose wiring, unstable input voltage, or issues with main circuit capacitors or the soft-charge bypass relay. Persistent undervoltage can lead to unreliable drive operation, component damage, or complete shutdown of the system.

Additional Steps

Steps 1–2 are listed in Priority Fix.

1. 3

   Check the maintenance status of main circuit capacitors using monitor U4-05 [CapacitorMaintenance]; if it exceeds 90%, plan for replacement of the control board or the entire drive.

2. 4

   Inspect the soft-charge bypass relay's performance life using U4-06 [PreChargeRelayMainte]; if it exceeds 90%, arrange for replacement of the relevant board or the drive itself.

3. 5

   Perform a Fault Reset to clear the fault from the drive after all identified power supply or component issues have been resolved.