Design theory of a variable characteristic motor using compound magnetomotive forces

The permanent magnet synchronous motor offers the possibility of obtaining higher efficiency in a smaller motor size. However, it is difficult to vary the range of high motor efficiency because of its constant magnetomotive force (MMF) level. This paper proposes a variable characteristic motor that embodies a new concept of the compound magnetomotive forces (CMMF) motor. The motor uses a special magnet arrangement that has the MMF of components with different number of pole pairs. The application of compound current control to this motor makes it possible to vary the motor speed and torque (N-T) characteristics. This paper describes the derivation of the theoretical equations for this CMMF motor. It also presents the results of FEA and experiments conducted with the prototype motor to demonstrate the validity of the CMMF concept.