Appeal No. 1998-3072 Page 2
Application No. 08/769,610
motor and associated control. Such a motor would be useful,
for example, in a household refrigerator.
The invention uses an output from a Hall sensor to
trigger sequential energization of a pair of stator windings
through switches. The sequential energization creates a
rotating magnetic field that reacts with the permanent
magnetic field of a rotor, causing the rotor's shaft to
rotate. Although the magnetic flux created by an energized
winding is proportional to current flow through the winding,
maximum torque, and hence maximum power output, is not
continuously produced during continuous maximum current flow
through the windings during operation of the motor. To the
contrary, changes in magnetic flux coupling result in
decreased motor torque during a portion of rotor rotation
notwithstanding the continuous application of full power to
the stator windings.
Figure 23 of the appellants' specification depicts the
phenomenon. The Figure plots current flow (proportional to
magnetic flux) through the windings against time and torque or
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