Efficiency Improvement of a Concentrated Winding Synchronous Reluctance Motor Using Sixth Harmonics Component of d and q-axis Currents

A concentrated winding synchronous reluctance motor (CW-SynRM) especially with a salient pole rotor is easy to manufacture, but has the large inductance harmonics, which also increase the flux harmonics. These flux harmonics cause the increase of the iron loss and decrease of the efficiency at high-speed range. In addition, these flux harmonics generate additional back-EMF, and decrease the maximum output power at high-speed range. Therefore, it is necessary to reduce the flux harmonics generated by the inductance harmonics. In this paper, an injection of the sixth-order harmonics currents into the d and q axes currents is proposed to reduce the sixth-order d and q axes fluxes. In the analysis, it is found that the injection of sixth-order d and q currents can reduce the sixth-order d and q axes fluxes, which also can reduce the iron loss and back-EMF. It is also found that the additional torque can be generated by the sixth-order d and q axes currents using the sixth-order d and q axes inductances, then, this additional torque can suppress the increase of the copper loss due to the injected current.