Main Circuit Overvoltage

What does %U mean?

This fault indicates that the DC voltage of the main circuit has exceeded its safe limit. If occurring while stopped (warning state), it typically means the power supply voltage is too high. If occurring when the protective mechanism is actuated (during operation), it's usually due to excessive regenerative energy from the motor, often caused by short deceleration times or overshoot during acceleration, pushing the DC bus voltage above approximately 410V (or 820V for 400-VAC Class). Unresolved overvoltage can damage inverter components.

• Incoming AC supply voltage is consistently above the inverter's specified high-voltage threshold (e.g., above 480VAC for a 400V class inverter).
• Power grid instability or voltage spikes occurring during low-load periods or line switching operations.
• Faulty voltage sensing circuit within the inverter providing an erroneous overvoltage detection.
• Incorrect inverter parameter settings for nominal input voltage (e.g., P2-01) leading to an inaccurate reference point.

Click steps to track your progress.

1. 1

   Measure the incoming AC supply voltage at inverter input terminals (R/L1, S/L2, T/L3) and confirm it is within the inverter's specified operating range.

2. 2

   Investigate for power grid instability or local factors causing overvoltage conditions, potentially requiring line reactors or a surge protector.

3. 3

   Verify that the inverter's input voltage parameter (e.g., P2-01 or P1-03) is correctly set to match the actual supply voltage.

4. 4

   Monitor the DC bus voltage ('Udc' on the display) in real-time to observe the peak voltage characteristics leading to the fault.

5. 5

   If equipped, check the functionality of any regeneration units or braking resistors if there's any possibility of regenerative energy feedback.