we recently had a problem with one of our fanuc spindle motors shorting down to earth, however the problem was not discovered untill a new amplifier unit was installed. prior to this the motor was fully tested and insulation teasted upto 1000v with no breakdown so it was asumed to be a faulty drive, with the motor disconcted the same no12 fault on the drive apeared. the drive was replaced and the spinlde ran upto full speed no problems occored however after 2 hours of running the new drive developed the same fault and the insultaion to earth on the motor down with 400v.
my question is
why did this not show up in testing earlia is there a special method for teasting the motors? just wanted to know for futur referance
btw alpha drives h405