Brake Control Fault

What does bLF mean?

Indicates a loss of one or more phases (3-phases) to the motor's brake. This fault can lead to uncontrolled motor movement if the brake fails to engage or disengage properly, posing a significant safety risk.

• Blown fuse in the 3-phase brake power circuit, interrupting one or more phases to the motor brake coil.
• Contactor or relay (e.g., K1 brake contactor) supplying power to the brake coils has failed or welded contacts.
• Open circuit in one phase of the brake wiring due to mechanical stress, corrosion, or poor connection at a terminal block.
• Incorrect brake coil resistance (e.g., not matching Parameter P4-12 setting) or wiring for the applied voltage.
• Drive's internal brake control circuit fault (e.g., output stage for the brake contactor coil) preventing activation.

Click steps to track your progress.

1. 1

   1. Disconnect all input power to the drive. Measure resistance across each phase of the motor brake coil and compare to manufacturer specifications.

2. 2

   2. With power OFF, visually inspect all fuses in the brake power circuit and test continuity across each fuse. Replace any open fuses.

3. 3

   3. Verify continuity of all three phase conductors from the drive's brake output terminals (e.g., TB1-U, TB1-V, TB1-W) to the motor brake.

4. 4

   4. Test the brake contactor (if external) for proper operation by manually actuating and checking continuity across its main power contacts.

5. 5

   5. Confirm drive parameters related to brake control (e.g., Brake enable, Brake release time, Parameter P4-12) are set correctly for the brake model.