Design of double salient interior permanent magnet machine based on mutually coupled reluctance machine for increasing the torque density and flux-weakening capability

This paper presents a novel structure of double salient interior permanent magnet machine (DSIPM machine) based on mutually coupled switched reluctance machine (MCSRM). Due to its salient rotor structure, the DSIPM machine can have less magnetic and iron materials as well as higher dynamic response than conventional IPM machines. The comparison of electromagnetic performances in terms of self and mutual inductances, d-axis and q-axis inductances, cogging torque, reluctance torque, total torque, torque ripple coefficient and flux-weakening capability between the DSIPM machine 6/8 and the DSIPM machine 12/8 has been realized. The numerical results based on Finite Element 2D shows that due to its much lower cogging torque and higher reluctance torque, the DSIPM machine 12/8 can produce higher total average torque than the DSIPM 6/8 at all phase current range. Furthermore, at low phase currents, the torque ripple of the DSIPM machine 12/8 is lower than that of the DSIPM machine 6/8, while at high phase currents, the torque ripples of these two machines are similar. Comparing to MCSRM, the DSIPM machines can produce higher average torque with lower torque ripple. Moreover, due to their high d-axis inductances, the two DSIPM machines can have theoretically “infinite” flux-weakening capability with relatively lower short-circuit currents.