In a PPMT motor the rotor is similar to a conventional Variable Reluctance Motor (VRM). VRMs are often used
for stepper motors. Like a VRM, the rotor of the PPMT motor is a high permeability iron laminate with no coils or
magnets on the rotor. That is where the similarity to a VRM ends. Unlike a VRM, the stator portion of the PPMT
motor includes permanent magnets. For each pair of magnets, two coils are wound onto the stator. In a
conventional VRM, coils are wound around each stator pole and the flux generated by current flowing in these
coils is used to generate torque. In the PPMT motor the permanent magnet flux plus the induced flux from
the load current add to generate the shaft torque. Torque is optimized by proper timing in the switching of
the stator coils. The coils provide a flux steering service in directing the permanent magnet’s flux to the proper
poles at the proper times to produce torque. Because of the supplemental power due to the permanent magnet flux,
the input power needed is substantially less than the power required by a conventional motor for each pound of
torque generated. Thus, the PPMT motor is much more efficient. PPMT motors have exceptional performance in
continuous duty applications. Compared to a conventional motor’s continuous duty rating, a PPMT motor will be
lighter, smaller, and higher efficiency than any conventional design.
