71A5 Mechanical Brake Opening Not Allowed Fault in ABB ACS880 Drive

71A5 Mechanical Brake Opening Not Allowed in the ABB ACS880 Drive indicates that the drive has prevented the mechanical brake from opening because the required opening conditions have not been satisfied. Before releasing the mechanical brake, the ACS880 verifies that all configured operating conditions and safety requirements have been met. If one or more of these conditions are not fulfilled, the drive generates Fault 71A5 and keeps the brake engaged.

71A5 Mechanical Brake Opening Not Allowed Fault in ABB ACS880 Drive


This is a programmable protection fault, and the drive's response is determined by Parameter 44.17 – Brake Fault Function. One common cause of this fault is Parameter 44.11 – Keep Brake Closed, which intentionally prevents the brake from opening.

Unlike a mechanical brake hardware failure, this fault usually indicates a configuration, logic, or operating condition issue rather than a defective brake.

Possible Causes

  • Parameter 44.11 – Keep Brake Closed is enabled.
  • Brake opening conditions have not been satisfied.
  • Incorrect configuration in Parameter Group 44 – Mechanical Brake Control.
  • Brake acknowledgement signal does not match the actual brake status.
  • Faulty brake acknowledgement switch or sensor.
  • Incorrect brake feedback wiring.
  • Loose or damaged brake control wiring.
  • Incorrect digital input configuration for brake acknowledgement.
  • External PLC or machine logic preventing brake release.
  • Brake control sequence interrupted.
  • Safety interlock preventing brake operation.
  • Incorrect operating state of the drive.
  • Internal control logic preventing brake release.
  • Faulty control board I/O.
  • Parameter changes made during commissioning without proper verification.

Solutions

  • Cycle power to the drive if appropriate and check whether the fault clears.
  • Verify Parameter 44.11 – Keep Brake Closed and disable it if brake release is required.
  • Review all settings in Parameter Group 44 – Mechanical Brake Control.
  • Verify that all brake opening conditions are satisfied.
  • Check the brake acknowledgement signal.
  • Ensure the acknowledgement signal correctly reflects the actual brake status.
  • Inspect the brake acknowledgement switch or proximity sensor.
  • Inspect brake control wiring for loose or damaged connections.
  • Verify the digital input assigned to brake acknowledgement.
  • Check any external PLC or machine control logic that may inhibit brake release.
  • Verify that all required drive operating conditions are met before brake opening.
  • Correct any parameter configuration errors.
  • Replace faulty brake feedback devices or wiring if necessary.
  • Contact ABB technical support if the fault persists after configuration and hardware inspection.

Additional Information

The ABB ACS880 includes advanced Mechanical Brake Control functions that ensure the brake is released only when all configured operating conditions have been met. This prevents unintended movement and improves operational safety in applications such as cranes, hoists, elevators, and vertical conveyors.

When the drive determines that one or more brake opening conditions are not satisfied, it keeps the brake engaged and generates Fault 71A5.

One of the most common reasons for this fault is Parameter 44.11 – Keep Brake Closed, which intentionally prevents brake release. This parameter is often used during maintenance, commissioning, or special operating modes.

The drive may also generate this fault if the brake acknowledgement signal does not correctly indicate the current brake status. In this case, even if the brake is physically capable of opening, the drive will prevent operation because it cannot safely verify the brake position.

Unlike Fault 71A3 – Mechanical Brake Opening Failed, where the drive commands the brake to open but the operation fails, Fault 71A5 indicates that the drive never allows the brake opening sequence to begin because the required conditions are not met.

Common Symptoms

  • Drive trips with Fault 71A5.
  • Motor will not start.
  • Mechanical brake remains engaged.
  • Brake opening sequence never begins.
  • Brake release command is inhibited.
  • Drive refuses to produce motor torque.
  • Fault appears immediately after a start command.
  • Brake acknowledgement signal remains inconsistent.
  • Fault occurs after parameter changes or commissioning.
  • Hoisting or vertical applications cannot begin movement.

Recommended Troubleshooting Sequence

  1. Cycle power to the drive if necessary.
  2. Check Parameter 44.11 – Keep Brake Closed.
  3. Review all settings in Parameter Group 44 – Mechanical Brake Control.
  4. Verify all brake opening conditions are satisfied.
  5. Check the brake acknowledgement signal.
  6. Inspect the brake acknowledgement wiring.
  7. Verify the brake acknowledgement switch or sensor.
  8. Check the digital input assigned to brake acknowledgement.
  9. Inspect brake control wiring and connectors.
  10. Verify external PLC or machine control logic.
  11. Confirm the drive is in the correct operating state for brake release.
  12. Correct any parameter configuration errors.
  13. Replace defective brake feedback devices or wiring if necessary.
  14. Verify proper brake operation after corrections.
  15. Contact ABB technical support if the fault persists.

Mechanical Brake Opening Permission Check Table

Check PointAction
Power cycleRestart the drive if required
Parameter 44.11Verify Keep Brake Closed setting
Parameter Group 44Verify Mechanical Brake Control settings
Brake opening conditionsConfirm all conditions are satisfied
Brake acknowledgement signalVerify it matches the actual brake status
Brake acknowledgement wiringInspect for loose or damaged connections
Brake acknowledgement switch/sensorVerify proper operation
Digital inputCheck brake acknowledgement input configuration
Brake control wiringInspect connections and terminals
External PLC logicVerify brake release is not inhibited
Drive operating stateConfirm conditions permit brake opening
ABB technical supportContact if the fault remains after inspection

Preventive Maintenance Tips

  • Review Parameter Group 44 settings after commissioning or maintenance.
  • Verify Parameter 44.11 – Keep Brake Closed is returned to its normal operating setting after maintenance activities.
  • Periodically test the brake acknowledgement signal for correct operation.
  • Inspect brake wiring and connectors during scheduled maintenance.
  • Verify digital input assignments after parameter modifications.
  • Test the complete brake control sequence following hardware or software changes.
  • Ensure external PLC logic is synchronized with the drive's brake control sequence.
  • Keep brake sensors and switches clean and correctly adjusted.
  • Use only ABB-approved or equipment manufacturer-approved brake control components.
  • Record recurring brake permission faults to assist long-term diagnostics.

Proper verification of Parameter Group 44 – Mechanical Brake Control, correct configuration of Parameter 44.11 – Keep Brake Closed and Parameter 44.17 – Brake Fault Function, confirmation of the brake acknowledgement signal, and routine inspection of brake control wiring and external control logic will help prevent recurring 71A5 Mechanical Brake Opening Not Allowed faults in ABB ACS880 drives, ensuring safe brake sequencing, reliable motor startup, and dependable long-term operation in applications requiring mechanical braking.

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