Power factor of three-phase flux reversal machines

Two main drawbacks of flux reversal machines (FRMs) are high cogging torque and low power factor, among which the latter one has not been addressed. This paper proposes an analytical method based on winding function theory to analyze the power factor of a FRM. Firstly, the back-EMF, synchronous inductance and power factor of a FRM are derived. With the employment of the equations, the main reason for low power factor is explored. Secondly, the effects of the main geometric parameters e.g. split ratio, slot opening width, and rotor pole embrace on the power factor and back-EMF are analytically investigated and analyzed. The results can be used to optimize and improve the power factor and back-EMF of a FRM. Finally, finite element analyses (FEA) are performed on a 12/16 FRM to validate the accuracy of the proposed method and good agreements have been achieved.