Cause : DC bus overvoltage comes when the voltage on the DC bus has exceeded the drive’s maximum allowable limit. This can happen due to several reasons, including regenerative energy from the motor, power supply issues, or problems with the drive's components.

The "OBF" fault in a Schneider ATV950 drive indicates an "overvoltage condition on the DC bus". This happens when the voltage in the internal storage capacitors of the drive exceeds the safe limits.

Steps to Address an "OBF DC Bus Overvoltage" Fault:

1. Immediate Actions:

   • Stop Operation: If the drive is running, stop it to prevent any potential damage or unsafe conditions.
   • Reset Error: Attempt to reset the error using the drive’s control panel. This may clear temporary issues.

2. Power Cycle the Drive:

   • Power Off: Turn off the power to the drive.
   • Wait: Wait for a few minutes to ensure all capacitors discharge fully.
   • Power On: Turn the power back on and see if the error persists.

3. Inspect the Power Supply:

   • Voltage Levels: Verify that the input voltage to the drive is within the specified range. Ensure there are no fluctuations or spikes.
   • Power Quality: Ensure the power supply is stable and free from transients or harmonics that could affect the drive.

4. Check DC Bus Components:

   • DC Bus Capacitors: Inspect the DC bus capacitors for signs of bulging, leakage, or damage. Faulty capacitors can cause overvoltage issues.
   • Brake Chopper and Resistor: If the drive has a brake chopper and resistor, ensure they are functioning correctly. A faulty brake resistor can cause overvoltage by not dissipating excess energy.

5. Regenerative Energy:

   • Deceleration Settings: Check the drive's deceleration settings. Rapid deceleration can cause regenerative energy to flow back into the drive, leading to overvoltage. Adjust the deceleration rate if necessary.
   • Regenerative Load: If the motor is regenerating energy (e.g., during braking or deceleration), ensure that the drive is equipped to handle it. Consider using a dynamic braking resistor to dissipate the excess energy.

6. Inspect Wiring and Connections:

   • Connections: Ensure all wiring and connections to the drive are secure and free from damage. Loose or faulty connections can cause voltage spikes.
   • Grounding: Verify that the drive and motor are properly grounded. Poor grounding can lead to electrical noise and overvoltage conditions.

7. Verify Configuration Settings:

   • Parameter Settings: Check the drive’s configuration settings related to voltage limits and braking. Ensure they are set according to the application requirements.
   • Voltage Monitoring: Ensure that the voltage monitoring settings are correctly configured to detect and respond to overvoltage conditions.