DC Bus Overvoltage

What does OU mean?

The DC bus voltage has exceeded its safe operating limit, primarily caused by an excessively high incoming mains voltage. This fault can also be triggered by regenerative energy from the motor if deceleration times are too short or the brake resistor is undersized/missing. Overvoltage poses a significant risk of damage to the drive's internal components, especially the DC bus capacitors and power semiconductors.

• Incoming mains supply voltage exceeding the drive's nominal input voltage (P2-04) plus tolerance.
• Regenerative energy from the motor during rapid deceleration or braking operations with insufficient dissipation (e.g., brake resistor undersized or faulty).
• Improperly sized or configured brake resistor (P6-30 to P6-33) for the application's inertia and deceleration rates.
• Faulty DC bus voltage measurement circuit within the drive controller, causing an incorrect reading.
• Loose or high-resistance connections in the braking circuit, preventing effective energy dissipation.

Click steps to track your progress.

1. 1

   Measure the incoming mains supply voltage (L1, L2, L3) using a true-RMS multimeter and verify it is within the drive's specified input voltage range.

2. 2

   Increase the deceleration time (e.g., P0-11, P0-12) to reduce the rate of regenerative energy feedback from the motor.

3. 3

   Verify the brake resistor's resistance value (P6-30) and power rating (P6-31) match the application requirements and the drive's specifications.

4. 4

   Check the connections of the brake resistor to the drive's braking terminals (e.g., B+, B-) for proper contact and low resistance.

5. 5

   Inspect the drive's internal DC bus capacitors for signs of bulging or leakage which could indicate a fault in the DC link.