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fanuc beta i servo alarm motor overheating


Jan 1, 2012
Savannah, Georgia, USA
I am troubleshooting a snk 5x mill. I have a SNK that runs Beta i servo for the ATC. We are getting a servo alarm 400 (The servo motor has overheated). I have replaced the motor, and even pulled the motor away from the gear box running in open air to eliminate gear box binding. When I turn on machine the shaft vibrates for a few minutes and then goes into alarm mode. Could this be coolant in the wires or a worn cable? I guess I could disconnect both ends and look for shorts.

steve austin
It could be. Could be a lot of things really.

You need a megger to check for bad cable and winding. You'd check each lead to ground, first disconnecting the cable from the drive but leaving it on the motor. If any of them read low, then disconnect the cable from the motor and check it again, to see if it was the cable or motor. (could also be the cable/motor connection)

Could be the drive, or encoder, or encoder connection, or electrical noise. But gut feeling always suggests cable first.
The high vibration may be heating up the motor, too.
Ohm/Meg cable to make sure no motor cable phases are open or shorted to GND. (Use appropriate cautions when using megaohm meter. Don't meg drive!)
Do a thorough parameter check to verify factory settings.
PMM parameter 102 is a torque command filter. See I/O Link MNT Manual.