Rotor flux-barrier geometry design to reduce iron losses in synchronous IPM motors under FW operations

The interior permanent magnet (IPM) synchronous motor is characterized by a high rotor anisotropy. Such an anisotropy is the cause of a high harmonic content of the air gap flux density distribution, almost independent of the main flux. As a consequence there are fluctuations of the flux density in the stator iron, and consequently eddy current iron losses. This aspect is prominently evident during flux-weakening operations, when the armature current weaken the PM flux and the motor runs above base speed. This paper presents a complete study of such a phenomenon, including an analytical model, a finite element validation, as well as an experimental confirmation of the predicted results. Finally, some suggestions are given in order to design an IPM motor exhibiting reduced iron losses during all operating conditions.