Finite element calculation of the dq-axes inductances and torque of synchronous reluctance motor

The most important parameters of a synchronous reluctance machine (SynRM) from a design optimization and control point of view are both the ratio and the difference between the inductances in the d and q axes, since they define the machine's characteristic such as torque and power factor. The direct-axis and quadrature-axis inductances of SynRM are usually considered as constant. In fact, both the d-axis and q-axis inductances vary with load conditions because of magnetic circuit saturation. In this paper a SynRM with salient-pole rotor is studied. Using finite element analysis, a procedure based on the energy perturbation method, is developed to calculate the self and cross-coupling inductances. The effect of saturation and cross saturation on the inductances behavior and on the produced torque is discussed.