Novel switched flux machine with radial and circumferential permanent magnets

In this paper, a novel switched flux permanent magnet (SFPM) machine topology with radial and circumferential permanent magnets (PMs) is proposed. In addition to the original circumferential PMs in the conventional SFPM machine, this topology (SFRCPM) has an additional set of radially magnetized PMs located around the back iron and surrounded by a laminated ring frame. The SFRCPM topology reduces the flux leakage in the stator outer region and consequently high magnetic material utilization can be achieved. Using finite element analysis (FEA) the influence of the design parameters is investigated in order to find an effective optimization procedure. Moreover, internal and external rotor SFRCPM machines with either NdFeB or ferrite magnets are investigated, optimized and compared with the conventional SFPM (CSFPM) machine having the same size, copper loss and stator/rotor pole combination. It is found that compared with its CSFPM machine counterpart, internal rotor SFRCPM machine can achieve high PM flux-linkage per magnet volume, however reduced slot area leads to low output torque whilst, external rotor SFRCPM machine can produce higher torque and torque per magnet volume.