DC Bus Undervoltage
Yaskawa · J1000 AC Drive
What does Uv1 mean?
The DC bus voltage fell below the undervoltage detection level (e.g., ~190V for 200V class, ~380V for 400V class) while the drive was running, or specific parameter conditions were met. Common causes include input power phase loss, loose wiring, unstable voltage supply, or worn main circuit capacitors.
Complete Troubleshooting Guide
- 1
Verify main circuit input power wiring for phase loss or loose terminals; correct wiring and apply specified tightening torque (refer to manual, page 76).
- 2
Check the input power voltage against drive specifications; if the supply is fine, inspect the main circuit magnetic contactor for proper operation.
- 3
Check the main circuit capacitor maintenance time (U4-05); if it exceeds 90%, consider replacing the control board or the entire drive.
- 4
Cycle power to the drive; if the fault reoccurs, inspect the soft-charge bypass relay or contactor and its performance life (U4-06). Replace the control board or entire drive if U4-06 exceeds 90% or the component is faulty.