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.