CHAPTER X
HYSTERESIS MOTOR
98. In a revolving magnetic field, a circular iron disk, or
iron cylinder of uniform magnetic reluctance in the direction of
the revolving field, is set in rotation, even if subdivided so as to
preclude the production of eddy currents. This rotation is due
to the effect of hysteresis of the revolving disk or cylinder, and
such a motor may thus be called a hysteresis motor.
Let I be the iron disk exposed to a rotating magnetic field
or resultant m.m.f. The axis of resultant magnetization in the
disk, I, does not coincide with the axis of the rotating field, but
lags behind the latter, thus producing a couple. That is, the
component of magnetism in a direction of the rotating disk, /,
ahead of the axis of rotating m.m.f., is rising, thus below, and
in a direction behind the axis of rotating m.m.f. decreasing, that
is, above proportionality with the m.m.f., in consequence of the
lag of magnetism in the hysteresis loop, and thus the axis of
resultant magnetism in the iron disk, I, does not coincide with
the axis of rotating m.m.f., but is shifted backward by an angle,
a, which is the angle of hysteretic lead.
The induced magnetism gives with the resultant m.m.f. a
mechanical couple:
D = m3r<i> sin a,
where
CF = resultant m.m.f.,
$ = resultant magnetism,
a = angle of hysteretic advance of phase,
m = a constant.
The apparent ,or volt-ampere input of the motor is:
P = wCF<$.
Thus the apparent torque efficiency:
P
Q = sm a,
where
Q = volt-ampere input,