71A3 Mechanical Brake Opening Failed Fault in ABB ACS880 Drive

71A3 Mechanical Brake Opening Failed in the ABB ACS880 Drive indicates that the drive has detected a mechanical brake control fault during the brake opening sequence. The ACS880 controls and monitors the mechanical brake through dedicated brake control logic and a brake acknowledgement feedback signal. If the brake does not release (open) as expected or the acknowledgement signal does not confirm the brake has opened within the configured time, the drive generates Fault 71A3 to prevent unsafe motor operation and possible damage to the motor or driven equipment.

This is a programmable protection fault, and the drive's response is determined by Parameter 44.17 – Brake Fault Function, which defines how the drive reacts when a mechanical brake fault is detected.

Possible Causes

  • Mechanical brake failed to open.
  • Brake acknowledgement signal not received.
  • Brake acknowledgement signal does not match the actual brake position.
  • Loose or damaged brake control wiring.
  • Faulty brake acknowledgement switch or sensor.
  • Incorrect wiring of the brake feedback signal.
  • Defective brake contactor or relay.
  • Brake coil failure.
  • Insufficient supply voltage to the brake coil.
  • Mechanical brake seized due to wear, corrosion, or contamination.
  • Brake spring or mechanical linkage failure.
  • Incorrect brake timing settings.
  • Incorrect configuration in Parameter Group 44 – Mechanical Brake Control.
  • Faulty digital input receiving the brake acknowledgement.
  • PLC or external brake control logic malfunction.
  • Internal control board I/O failure.

Solutions

  • Cycle power to the drive and check whether the fault clears.
  • Inspect the mechanical brake for proper operation.
  • Verify that the brake opens completely before motor startup.
  • Check the brake control wiring for loose or damaged connections.
  • Verify the brake acknowledgement wiring.
  • Ensure the acknowledgement signal correctly reflects the actual brake status.
  • Inspect the brake acknowledgement switch or proximity sensor.
  • Check the brake coil voltage and operation.
  • Inspect the brake contactor or relay.
  • Verify all settings in Parameter Group 44 – Mechanical Brake Control.
  • Review Parameter 44.17 – Brake Fault Function.
  • Check the associated digital input used for brake acknowledgement.
  • Repair or replace defective brake components.
  • Replace faulty wiring or connectors.
  • Contact ABB technical support if the fault persists after mechanical and electrical inspection.

Additional Information

The ABB ACS880 provides integrated mechanical brake control for applications such as cranes, hoists, elevators, winches, and other systems that require a holding brake.

Before the motor is allowed to produce torque, the drive commands the mechanical brake to open (release). The brake acknowledgement device, typically a limit switch or proximity sensor, must confirm that the brake has fully released within the configured time.

If the acknowledgement signal does not change to the expected state, the drive generates Fault 71A3 because it cannot verify that the brake has opened safely.

The drive's response is determined by Parameter 44.17 – Brake Fault Function, while the brake operating sequence, timing, and acknowledgement settings are configured in Parameter Group 44 – Mechanical Brake Control.

Unlike Fault 71A2 – Mechanical Brake Closing Failed, which occurs during brake application after stopping, Fault 71A3 occurs before motor operation when the brake fails to release or its feedback signal does not confirm successful opening.

Common Symptoms

  • Drive trips with Fault 71A3.
  • Motor does not start.
  • Mechanical brake remains engaged.
  • Brake acknowledgement signal remains incorrect.
  • Drive refuses to enable motor torque.
  • Brake relay operates but the brake does not release.
  • Fault appears during startup.
  • Brake control sequence is interrupted.
  • Fault remains after reset until the brake opens correctly.
  • Hoisting or vertical applications cannot begin movement.

Recommended Troubleshooting Sequence

  1. Cycle power to the drive.
  2. Inspect the mechanical brake for proper operation.
  3. Verify the brake opens completely.
  4. Check the brake control wiring.
  5. Inspect the brake acknowledgement wiring.
  6. Verify the acknowledgement signal changes correctly.
  7. Inspect the brake acknowledgement switch or sensor.
  8. Check the brake coil voltage.
  9. Inspect the brake contactor or relay.
  10. Verify all settings in Parameter Group 44 – Mechanical Brake Control.
  11. Review Parameter 44.17 – Brake Fault Function.
  12. Verify the digital input assigned to brake acknowledgement.
  13. Replace defective brake components or wiring if necessary.
  14. Verify proper brake sequencing after repairs.
  15. Contact ABB technical support if the fault persists.

Mechanical Brake Opening Check Table

Check PointAction
Power cycleRestart the drive
Mechanical brakeVerify complete brake opening
Brake control wiringInspect for loose or damaged connections
Brake acknowledgement wiringVerify correct wiring
Acknowledgement signalConfirm it matches the actual brake status
Brake acknowledgement switch/sensorInspect operation
Brake coilVerify correct voltage and operation
Brake contactor / relayInspect for proper switching
Parameter Group 44Verify Mechanical Brake Control settings
Parameter 44.17Verify Brake Fault Function configuration
Digital inputCheck brake acknowledgement input
ABB technical supportContact if the fault remains after inspection

Preventive Maintenance Tips

  • Inspect the mechanical brake regularly for wear, corrosion, and free movement.
  • Verify brake pads, springs, and moving components are in good condition.
  • Periodically test the brake acknowledgement signal during maintenance.
  • Inspect brake wiring, connectors, and terminals for secure connections.
  • Verify brake coil voltage and current during release operations.
  • Keep the brake mechanism clean and lubricated according to the brake manufacturer's recommendations.
  • Review Parameter Group 44 settings after commissioning, maintenance, or hardware replacement.
  • Test complete brake release before returning the equipment to service.
  • Use only ABB-approved or equipment manufacturer-approved brake components.
  • Record recurring brake opening faults to assist long-term diagnostics.

Proper inspection of the mechanical brake, verification of the brake acknowledgement signal, correct configuration of Parameter Group 44 – Mechanical Brake Control and Parameter 44.17 – Brake Fault Function, and routine maintenance of the brake mechanism, control wiring, and feedback devices will help prevent recurring 71A3 Mechanical Brake Opening Failed faults in ABB ACS880 drives, ensuring reliable brake release, safe motor startup, and dependable long-term operation in applications requiring mechanical braking.

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