Current limit set too high by the sound of it!!.
If the servo drive is capable of 30 amps continuous say, the drive is OK supplying that current but if the motor is stalled it could be well out of the continuous torque rating of the motor. the motor is not capable of producing BEMF to reduce the current.
Fortunately not relevant *in this case*. The motor was not stalled, it was oscillating. The servo amp was pumping some serious AC power into the motor, which was getting hot due to high frequency eddy currents in the steel. I doubt the current levels were all that high in fact.
IF the servo was smoking hot and leaking grease I would replace the motor.
Yeah, serious thought was given to that. Perhaps 'smoking' is a bit of an exaggeration - I would say the motor had reached 50 - 60 C when i shut it down. Just a shade too hot to touch. I think the smell was due to some grease being near the brushes and getting vaporised.
Yes, this does bring into question the state of the brushes and the commutator. Unknown at present, but spinning freely.
I think (he says very hopefully), that the fault had only just happened, so that no great amount of damage had been done to the motor. For the present I will see how it goes with the existing motor.
All very educational. Shows the value of human supervision at all times! Hit eStop when one leaves for any significant length of time is the obvious answer, except that one always loses precise registration that way. Hum ...
Cheers