Principle of a variable characteristic motor with 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 permanent magnets are used for the rotor to obtain a certain level of magnetomotive force. This paper proposes a variable characteristic motor that embodies a new concept of compound magnetomotive forces. The motor uses a special magnet arrangement that has the magnetomotive forces of components with different numbers of pole pairs. The application of compound current control to this motor makes it possible to vary the motor speed and torque characteristics. This paper describes the derivation of the theoretical equations for this compound magnetomotive force motor. It also presents the results of a FEA and experiments conducted with a test motor to demonstrate the validity of the fundamental concept of the proposed motor.