Delta VFD ovA Fault – Overvoltage During Acceleration

The ovA (Overvoltage During Acceleration) fault in a Delta Variable Frequency Drive (VFD) indicates that the DC bus voltage has exceeded the overvoltage protection level while the motor is accelerating. To protect the inverter's power devices (IGBTs), the drive immediately shuts off the output and trips with the ovA fault.

Delta VFD ovA Fault – Overvoltage During Acceleration


Although overvoltage faults commonly occur during deceleration, ovA occurs specifically during acceleration, usually due to unstable input power, regenerative loads, incorrect parameter settings, or braking system issues.

Possible Causes

  • Input power voltage is too high.
  • Sudden increase in supply voltage.
  • Regenerative load during acceleration.
  • Incorrect acceleration parameter settings.
  • Incorrect wiring of the brake resistor or braking unit.
  • Brake resistor or braking unit malfunction.
  • AC reactor not installed where required.
  • Motor ground fault.
  • Electrical interference.
  • Drive hardware fault (rare).

Solutions

1. Input Power Voltage Too High

  • Check whether the incoming power voltage is within the rated input voltage range of the drive.
  • Check for temporary voltage surges on the mains supply.

2. Power Supply Voltage Fluctuation

  • Stabilize the incoming power supply.
  • Eliminate abnormal voltage spikes if present.

3. Regenerative Energy During Acceleration

  • Reduce the acceleration rate if the application allows.
  • Review application conditions that may cause regenerative energy during acceleration.

4. Incorrect Acceleration Settings

  • Increase the acceleration time.
  • Enable S-curve acceleration if available.
  • Use automatic acceleration functions where applicable.

5. Brake Resistor or Braking Unit

  • Check the wiring of the brake resistor and braking unit.
  • Verify that the resistor is correctly sized.
  • Replace defective braking components if necessary.

6. Motor Ground Fault

  • Inspect the motor cable.
  • Check the motor terminal box.
  • Measure the insulation resistance of the motor and motor cable.
  • Repair any ground fault before restarting.

7. Electrical Interference

  • Verify proper grounding of the drive.
  • Separate control wiring from power wiring.
  • Install an AC reactor if recommended for the application.

8. Hardware Failure

  • If all external conditions are normal and the fault persists, inspect the DC bus voltage sensing circuit and power module.
  • Repair or replace the drive if necessary.

Additional Information

The ovA fault is generated when the drive detects excessive DC bus voltage during motor acceleration.

Typical causes include:

  • High input voltage.
  • Utility voltage spikes.
  • Improper braking circuit.
  • Ground faults.
  • Incorrect acceleration settings.
  • Electrical noise or interference.

Prompt correction helps prevent damage to the inverter power section.

Common Symptoms

  • Drive displays ovA.
  • Motor trips during acceleration.
  • Drive stops immediately after starting.
  • DC bus voltage rises rapidly.
  • Repeated overvoltage trips during startup.
  • Production interruptions.

Recommended Troubleshooting Sequence

  1. Verify that the displayed fault is ovA.
  2. Disconnect power and follow lockout/tagout procedures.
  3. Measure the incoming supply voltage.
  4. Check for abnormal voltage fluctuations.
  5. Increase the acceleration time.
  6. Verify the brake resistor and braking unit wiring.
  7. Inspect the motor and motor cable for ground faults.
  8. Check the grounding and routing of control wiring.
  9. Install an AC reactor if required.
  10. Reset the fault and confirm normal operation.

ovA Overvoltage During Acceleration Check Table

Check PointAction
Input voltageVerify within rated range
Supply voltage stabilityCheck for voltage spikes
Acceleration timeIncrease if necessary
Brake resistorVerify wiring and sizing
Braking unitCheck operation
Motor cableInspect for ground faults
Motor insulationMeasure insulation resistance
GroundingVerify proper grounding
AC reactorInstall if recommended
Drive hardwareInspect if the fault persists

Preventive Maintenance Tips

  • Maintain a stable incoming power supply.
  • Use acceleration times appropriate for the application.
  • Regularly inspect brake resistor and braking unit wiring.
  • Periodically measure motor insulation resistance.
  • Keep control wiring separated from power cables.
  • Ensure proper grounding of the drive and motor.
  • Install AC reactors where recommended by Delta.
  • Record recurring ovA faults to identify developing power quality or hardware issues.
  • Inspect power terminals and cable connections during routine maintenance.
  • Follow Delta preventive maintenance recommendations for your VFD model.

Proper inspection of the input power supply, acceleration settings, braking system, motor insulation, grounding, and DC bus circuit will help prevent recurring ovA – Overvoltage During Acceleration faults in Delta VFDs, ensuring reliable operation and protecting the inverter from excessive DC bus voltage.

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