B&R Servo Drive Input Out-of-Phase Fault Repair

If the B&R drive detects an input out of phase, the keypad will display “PF”.

This fault occurs when the input power supply to the drive is out of phase or has a large phase-to-phase voltage imbalance. This fault is detected when parameter L8-05 is enabled (set to 1).

Probable Cause:

1. Missing phase of inverter input power supply
2. Loose connection of power input terminals
3. Excessive fluctuation of the drive input power supply voltage
4. Poor voltage balance between input power supply phases
5. Worn main circuit capacitors

Recommended Measures:

Check the main circuit of the input power supply to the B&R actuator and correct any errors.

Ensure that the terminals are properly tightened. Apply the tightening torque specified in the B&R drive manual to tighten the connections.

Check the voltage of the drive input power supply. If necessary, stabilize the input power (method outlined in the drive manual). You can also disable input out-of-phase detection in parameter L8-05 (set to 0), but this is not recommended to extend the life of the drive. This fault is detected if the DC BUS ripple is too high, so if this parameter is disabled and the ripple is too high, the capacitors will be put under more stress and lose life.

Check the maintenance time of the inverter capacitors in parameter U4-05. If the value at U4-05 is greater than 90%, replace the main capacitor.