DC Bus Overvoltage

What does ObF mean?

The DC bus voltage inside the drive has exceeded its safe operating limit. This is most commonly caused by regenerative energy from the motor, particularly during rapid deceleration of high-inertia loads, or by an excessively high incoming line voltage. Unresolved overvoltage can lead to damage to the drive's internal power components.

• Rapid deceleration of a high-inertia load without an adequately sized braking resistor or braking unit.
• Input line voltage (e.g., L1-L2, L2-L3, L3-L1) exceeding the drive's maximum rated voltage during operation.
• Motor cable capacitance (especially with long cables) causing voltage spikes during IGBT switching.
• Faulty internal DC bus voltage measurement circuit providing an incorrect reading.
• Incorrectly set acceleration/deceleration ramps (e.g., P1-03, P1-04) that are too short for the connected load.

Click steps to track your progress.

1. 1

   1. Measure the input line voltage (e.g., L1-L2, L2-L3, L3-L1) to ensure it is within the drive's specified limits.

2. 2

   2. Increase the deceleration ramp time (e.g., Parameter P1-04) to reduce regenerative energy during stops.

3. 3

   3. Verify the braking resistor (if installed) is correctly sized (e.g., Ohm value, Wattage) and wired to the drive's terminals (e.g., BR+ to BR-).

4. 4

   4. Check the resistance of the braking resistor; verify it is not open-circuit or short-circuit.

5. 5

   5. Inspect the motor cable for proper shielding and ensure its total length is within the drive's specifications.

6. 6

   6. Monitor the DC bus voltage (e.g., via HMI or serial communication) during operation to pinpoint the exact overvoltage event.