A Novel Rotor Design of Interior Permanent-Magnet Synchronous Motors to Cope with Both Maximum Torque and Iron-Loss Reduction

A novel rotor design of interior permanent-magnet synchronous motors (IPMSMs) has been developed in order to cope with both maximum torque and iron-loss reduction for wide-speed-range applications. First, the flux barrier and permanent-magnet shapes of an IPMSM are determined by using an automatic optimization method. In this optimization, the iron loss of the IPMSM under flux-weakening control at high speeds is minimized under the constrained condition of maximum torque at low speeds. As a result, a novel rotor, which has inner magnetic pole bodies, is obtained. The effectiveness of this design is discussed from both results of the finite-element analysis (FEA) and the measurement of a prototype motor. It is revealed that the iron loss of the proposed IPMSM at high speeds is significantly reduced, whereas the maximum torque decreases by only a few percent.