DC Bus Overvoltage

What does ov mean?

The DC bus voltage exceeded its trip point (e.g., ~410V for 200V class, ~820V for 400V class). This can result from surge voltage in the drive input power, a short-circuited motor, ground current over-charging the main circuit capacitors, or electrical signal interference affecting measurements.

• Excessive input AC line voltage (e.g., exceeding 480VAC for 400V class drives) causing the rectified DC bus voltage to rise above the trip point (~820V for 400V class).
• Rapid deceleration of a high-inertia load, generating regenerative energy that over-voltages the DC bus if dynamic braking is insufficient.
• Incorrectly sized or faulty dynamic braking resistor (e.g., resistance too high, power rating too low) or a disconnected braking resistor.
• Deceleration time setting (e.g., C1-04) is too short for the connected load inertia, leading to an abrupt energy return to the DC bus.
• A short circuit in the motor windings or motor cable causing severe current fluctuations that affect the DC bus voltage measurement.

Click steps to track your progress.

1. 1

   Measure the incoming AC line voltage at the drive input terminals (R, S, T) using a multimeter to confirm it is within the drive's specified operating range.

2. 2

   Verify the connection, functionality, and resistance of the external dynamic braking resistor (if installed) across terminals B1-B2 using an ohmmeter, comparing it to the specified value.

3. 3

   Increase the deceleration time setting in Parameter C1-04 (Deceleration Time 1) to allow for slower deceleration and reduced regenerative energy feedback.

4. 4

   Inspect motor wiring for shorts or ground faults, measuring insulation resistance between each motor phase (U, V, W) and ground, and between phases using a megohmmeter.

5. 5

   If a regenerative unit is used, verify its operational status, input voltage, and parameter settings (e.g., R1-01, R1-02).