Technical FAQs

Ask a Question

What are the probable causes of Braking Unit Fault (BUF) fault in Altivar 71 drive.

BUF is a Braking Unit Fault. This fault appears only for the drives > 90kW. This fault appears when there is
a short-circuit on the output of the braking transistor (desaturation of the braking IGBT).
Probable Causes:-
- Bad value of the braking resistor (too low)
- The braking resistor is in short circuit to the ground
- The braking transistor is defect
- The connection with the braking module is wrong
- Short circuit inside the braking module.
- BRA=NO (ramp autoadaptation) and no breaking resistor.
Was this helpful?
What can we do to improve the information ?