The present invention provides an external rotor stepper motor consisting
of four individual, independently controlled, co-planar stepper motors
optimized for vehicle direct wheel drive applications. The innovative
design eliminates the need for bifilar coil winding, each of the motors'
coils being single conductor, each coil being wound in the same direction
throughout the entire motor. Each of the four independent motors is
simultaneously energized. Because adjacent, outside coils of adjacent
motors are simultaneously energized at the same polarity, there is
substantially no energy wasting cancellation of magnetic flux. Carefully
chosen radially spacing of the four independent, co-planar motors also
eliminates substantially all flux interaction between the motors. Because
similar coils of the four motors are all connected in parallel, the net
inductance presented driver circuits is minimized. This yields fast rise
time pulses and improved efficiency through minimized reactance of the
motor.
