I am having an issue with the VFD in the subject line not building enough motor torque to release the brakes (Controlled by PLC). It is in a 2 motor drilling application where when the other motor is assigned it works perfectly.

We recently replaced the Level A thyristor as it was shorted and blew4 x fuses.

There are no faults on the inverter or rectifier PMU.

Kind of at a loss here as all encoder wiring is verified correct and have the correct pulses on it.
Also have verified all IGBT's are not shorted, replaced the CUVC card with a known working unit (installed proven parameter set)

Any help would be appreciated

Iwill try that when I get a chance today.

As far as the logic to release the brakes,the drives aretold via profibustotorque up to the required level to hold the load.If the torque isenough to hold the load the brakes are released.

With the other motor and drive and the same load the brakes are released no problem.

Initially the drive had a F002 fault that ended up being a shorted thyristor and 4 x open fuses.