Performance improvement of ferrite-assisted synchronous reluctance machines using asymmetrical rotor configuration

Recently, the demand for developing high performance electric machines which are free of rare earth magnets are becoming more and more attractive since the raw materials in the rare earth magnets suffer the challenge of increased price and limited supply. In particular, the ferrite-assisted synchronous reluctance machines (FA SynRMs) are regarded as one competitive candidate which incorporate the advantages of the permanent magnet synchronous machines (PMSMs) and synchronous reluctance machines (SynRMs). However, all the reported research for FA SynRMs is performed on a fact that the magnets are inserted in the central rotor flux barriers. Thus the rotor shape maintains circumferential symmetry such that the magnetic torque and the reluctance torque obtained from an d-q rotor frame equivalent circuit reach the maximum value at different current phase angles theoretically by 45° (elec.) with each other. Hence, only a portion of each torque component is effectively utilized. Nevertheless, the situation can be improved by taking advantage of the design concept in [4], in which the maximum values of torque components can meet near or at the same current phase angle by flux barrier design in a V-type IPM machine.