7191 BC Short Circuit Fault in ABB ACS880 Drive

7191 BC Short Circuit in the ABB ACS880 Drive indicates that the drive has detected a short circuit in the Brake Chopper (BC) IGBT. The brake chopper uses an Insulated Gate Bipolar Transistor (IGBT) to switch regenerative energy into the brake resistor during motor deceleration. The ACS880 continuously monitors the brake chopper circuit, and if it detects a short-circuited IGBT or an abnormal condition in the braking circuit, it generates Fault 7191 to protect the drive from severe damage.

7191 BC Short Circuit Fault in ABB ACS880 Drive


This fault generally indicates a problem with the brake chopper IGBT, brake resistor, or braking circuit, rather than a fault in the motor itself.

Possible Causes

  • Short circuit in the brake chopper IGBT.
  • Failed brake chopper module.
  • Damaged or shorted brake resistor.
  • Brake resistor not connected.
  • Incorrect brake resistor specifications.
  • Brake resistor resistance below ABB requirements.
  • Loose or damaged brake resistor wiring.
  • Short circuit in the brake resistor cables.
  • Internal brake chopper control failure.
  • Damaged brake chopper PCB.
  • Electrical surge damaging the brake chopper.
  • Internal power unit hardware failure.
  • Burned PCB tracks or power components.
  • Moisture or contamination causing electrical leakage.
  • Failure following incorrect brake resistor installation.
  • Aging or failure of brake chopper power electronics.

Solutions

  • Disconnect power and follow all electrical safety procedures before inspection.
  • Verify that a brake resistor is installed if required by the application.
  • Inspect the brake resistor for visible damage.
  • Measure the brake resistor resistance and compare it with the values specified in the ABB Hardware Manual.
  • Verify that the brake resistor electrical specifications are correct for the drive.
  • Inspect the brake resistor wiring for loose connections, insulation damage, or short circuits.
  • Verify all brake resistor terminals are securely connected.
  • Inspect the brake chopper circuit for signs of hardware failure.
  • Check the brake chopper IGBT for short circuit or physical damage.
  • Replace the brake resistor if damaged or out of specification.
  • Replace damaged wiring or connectors.
  • Replace the brake chopper (if replaceable).
  • Replace the power unit if the brake chopper is integrated and cannot be replaced separately.
  • After correcting the cause of the fault, reboot the control unit using Parameter 96.08 – Control Board Boot or by cycling power.
  • Contact ABB technical support if the fault persists after hardware replacement.

Additional Information

The ABB ACS880 uses a brake chopper to control regenerative energy generated during motor deceleration or when operating overhauling loads. The brake chopper switches a high-power IGBT on and off, directing excess DC bus energy into the brake resistor where it is safely dissipated as heat.

If the drive detects that the brake chopper IGBT has become short circuited, it immediately generates Fault 7191 to prevent catastrophic damage to the power electronics.

A damaged or incorrectly specified brake resistor can place excessive stress on the brake chopper IGBT, eventually leading to failure. For this reason, ABB recommends verifying that the brake resistor is connected correctly and that its electrical specifications comply with the Hardware Manual before replacing any hardware.

After repairing the braking circuit, the control unit must be rebooted using Parameter 96.08 – Control Board Boot or by cycling power so the drive can reinitialize the brake chopper diagnostics.

Common Symptoms

  • Drive trips with Fault 7191.
  • Fault occurs during braking or rapid deceleration.
  • Drive will not start after the fault.
  • Brake chopper protection activates immediately after power-up.
  • Braking function becomes unavailable.
  • Brake resistor may show signs of overheating or damage.
  • Fault remains after reset until the control unit is rebooted.
  • Frequent faults during high-regeneration applications.
  • Visible damage may be present on the brake chopper hardware.
  • Drive remains locked in a fault state until repairs are completed.

Recommended Troubleshooting Sequence

  1. Disconnect power and observe all electrical safety procedures.
  2. Verify that a brake resistor is installed if required.
  3. Inspect the brake resistor for physical damage.
  4. Measure the brake resistor resistance.
  5. Compare the resistor specifications with the ABB Hardware Manual.
  6. Inspect brake resistor wiring for loose connections or short circuits.
  7. Verify all brake resistor terminals are securely connected.
  8. Inspect the brake chopper hardware.
  9. Check the brake chopper IGBT for short circuit.
  10. Replace the brake resistor if defective.
  11. Replace damaged wiring or connectors.
  12. Replace the brake chopper if it is replaceable.
  13. Replace the power unit if the brake chopper is integrated and defective.
  14. Reboot the control unit using Parameter 96.08 – Control Board Boot or by cycling power.
  15. Contact ABB technical support if the fault persists.

BC Short Circuit Check Table

Check PointAction
Power isolatedEnsure safe working conditions before inspection
Brake resistorVerify it is installed and not damaged
Resistance valueMeasure and compare with ABB Hardware Manual specifications
Brake resistor specificationsConfirm correct electrical rating
Brake resistor wiringInspect for loose connections or short circuits
Brake resistor terminalsEnsure secure electrical connections
Brake chopper IGBTCheck for short circuit or physical damage
Brake chopperInspect for hardware failure
Power unitInspect if brake chopper is integrated
Parameter 96.08Reboot the control board after repairs
Power cycleRestart the drive if required
ABB technical supportContact if the fault remains after inspection

Preventive Maintenance Tips

  • Inspect the brake resistor and brake chopper during scheduled maintenance.
  • Periodically measure the brake resistor resistance to verify it remains within ABB specifications.
  • Always use a brake resistor with electrical ratings approved for the drive.
  • Inspect brake resistor wiring for signs of wear, overheating, or insulation damage.
  • Ensure brake resistor terminals remain tight and corrosion-free.
  • Maintain adequate cooling around the brake resistor and brake chopper.
  • Protect the braking circuit from electrical surges and transient voltages.
  • Replace damaged braking components promptly to prevent secondary failures.
  • Reboot the control unit using Parameter 96.08 – Control Board Boot after replacing braking hardware, if recommended.
  • Record recurring brake chopper faults to assist long-term diagnostics.

Proper inspection of the brake resistor, verification of its electrical specifications, routine maintenance of the brake chopper IGBT and braking circuit, and timely replacement of defective braking components will help prevent recurring 7191 BC Short Circuit faults in ABB ACS880 drives, ensuring safe dissipation of regenerative energy, reliable braking operation, and long-term protection of the drive's power electronics.

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