A79B BC Short Circuit Warning in ABB ACS880 Drive

A79B BC Short Circuit Warning in ABB ACS880 Drive indicates that a short circuit has been detected in the brake chopper IGBT (Insulated Gate Bipolar Transistor). The brake chopper controls the flow of regenerative energy from the DC bus to the brake resistor during motor deceleration. If the chopper IGBT becomes short-circuited, the drive generates this warning to prevent further damage.

This warning usually points to a hardware fault in the brake chopper circuit or a problem with the brake resistor connection.

Possible Causes:

  1. Short circuit in the brake chopper IGBT.
  2. Failed brake chopper module.
  3. Damaged brake resistor.
  4. Brake resistor wiring short circuit.
  5. Incorrect brake resistor installation.
  6. Brake resistor resistance value too low.
  7. Overloaded brake chopper.
  8. Internal power component failure.
  9. Damaged brake chopper control circuitry.
  10. Excessive regenerative braking energy causing hardware damage.

Solutions:

  1. Check that the brake resistor is connected properly.
  2. Inspect the brake resistor for signs of damage, overheating, or burn marks.
  3. Measure the brake resistor resistance and compare it with ABB specifications.
  4. Inspect brake resistor wiring for short circuits or insulation damage.
  5. Verify that the brake resistor is correctly sized for the application.
  6. If an external brake chopper is installed, replace the brake chopper if faulty.
  7. For drives with an internal brake chopper, the drive may require repair or replacement by ABB service.
  8. Check the brake chopper IGBT using appropriate test equipment.
  9. Inspect the braking circuit for wiring errors.
  10. After repairs, test the drive during controlled deceleration.

Additional Information

The brake chopper is responsible for protecting the DC bus from overvoltage during regenerative operation by directing excess energy into the brake resistor.

Common applications that heavily utilize brake choppers include:

  • Cranes and hoists
  • Elevators
  • Centrifuges
  • Conveyors
  • Winders and unwinders
  • High-inertia machinery

If the brake chopper cannot operate correctly, the drive may also experience:

  • DC Link Overvoltage Faults
  • Reduced braking performance
  • Unexpected drive trips
  • Damage to braking components

Recommended Troubleshooting Sequence

  1. Inspect the brake resistor connection.
  2. Check brake resistor condition and resistance value.
  3. Verify brake resistor sizing.
  4. Inspect brake resistor wiring.
  5. Test the brake chopper IGBT.
  6. Determine whether the chopper is internal or external.
  7. Replace faulty external brake chopper if required.
  8. Contact ABB service for internal brake chopper failures.

Related Faults and Warnings

CodeDescription
A79BBC Short Circuit Warning
7191BC Short Circuit Fault
A791Brake Resistor Warning
A794Brake Resistor Data Warning
3210DC Link Overvoltage Fault

Preventive Maintenance Tips

  • Regularly inspect brake resistor wiring and terminals.
  • Verify brake resistor resistance during maintenance.
  • Ensure brake resistor ventilation is adequate.
  • Check braking duty cycle against resistor specifications.
  • Inspect brake chopper components for signs of overheating.

Proper brake resistor installation, correct resistor sizing, and regular inspection of the braking circuit will help prevent recurring A79B BC Short Circuit Warnings in ABB ACS880 drives.

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