BSH Motor Holding Brake Failures

[VaughnKretzmann]

We were called to a machine with the following Servo equipment:

3 X LXM05AD57N4

3 X BSH1402P11F2A

Controlled by a TSX37 PLC via CAN.

The customer has lost 8 servomotors on this machine in a short space of time.  All the failures were the mechanical holding brake coil that had failed/burnt.  The resistance is lower than the typical 23ohms and then the brake does not disengage when power is applied to the brake.   

The next item to fail is the Servo Motor Power cable.   The pin on one of the motor phases is found to be shorter and it is black inside the connector indicating arcing from the pin that has "melted" due to excessive motor current possibly because the brake is not disengaging.

We will investigate the parameters in the LXM05 if they are correct to protect the motor and cable from overcurrent but what we have found is that the OEM did not use a HBC holding brake controller and the brake is controlled from the TSX37 PLC via a mechanical relay.   

We are going to do a more thorough investigation when we return to site but our question is: 

Would the failure of the brakes be due to the fact that there is no voltage reduction?   

The HBC controller has the facility to reduce the holding brake voltage after 1s to reduce the power and heat  but in the LXM05 manual it indicates that this should be switched on for SER motors but not for BSH motors.   The LXM32 has the HBC controller built into the Servo Drive and does not seem to have the option to switch off the voltage reduction.

Could someone confirm whether the voltage reduction is definitely required for the BSH motors and if we are correct in thinking that this is the probable cause of the mechanical brakes failing?

[VaughnKretzmann]

@Vikash_Rampathi please can you try elevate this issue to someone who can assist as the client needs a solution as soon as possible.