Field weakening performance of a synchronous motor with two-part rotor

A synchronous motor with two-part rotor is studied whose rotor comprises a surface-magnet part and an axially-laminated reluctance part mounted adjacent to each other on the same axis. This construction is a candidate for applications such as electric vehicles which require a constant-power speed range to be achieved by field weakening. Test results for an experimental 4-pole motor give nearly ideal constant input power, with high power factor, in agreement with computed predictions. Measured output powers indicated the occurrence of additional losses which are believed to occur in the axially-laminated reluctance part.