A conventional servo motor converts electrical energy into rotational motion. It comprises stator windings and housing, permanent magnet rotor and laminates, pulse coder and end rear bell along with front and rear bearings.
The stator windings and housing represent the electromagnetic part of the servo motor. Its C-face mounting secures it to the frame of a machine or load that is to be controlled. Its ferrous core, made of steel laminates, focuses the magnetic field produced when electrical current flows in the copper winding. Embedded in the stator laminates, the copper winding is a 3-phase winding in FANUC’s star configuration. For each revolution of output from a servo motor, the 3-phase input power must be cycled four times. Hence, FANUC servo motors are built in what’s referred to as quadrature.
The motor rotor is the rotating part of the motor that is usually coupled to a ball screw. It is made of an output shaft that is centered in an iron mass constructed of steel laminates. The rotor is suspended by a pair of bearings holding the output shaft in the center of the stator. The rotor’s magnetic field is made of permanent magnets that are embedded in the rotor. Usually, four pairs of north-south magnets exist, making most FANUC servo motors 8-pole motors.