Evaluation of inductance in a permanent magnet synchronous motor

The performance of a permanent magnet synchronous motor (PMSM) drive highly depends on the machine parameters such as resistance, inductance and back-emf constant. The accurate knowledge of these parameters is of specific interest in the case of direct torque control method (feed forward control) and sensor-less control. The knowledge of the machine inductance always poses some extra degrees of challenge due to its dependency on the saturation effect and the non-linear B-H curve of the magnetic steels. The inductance of the PMSM is used in determining the control voltage and estimation of motor position. This paper is an attempt to provide guidance to the methodologies to determine the inductance of PMSMs using analytical and finite element (FE) modeling. The dq-model of the PMSM machine is used to calculate the synchronous inductances. The theoretical and FE simulation result are compared to the test results to verify the reliability of different techniques for inductance measurement for both theoretical and practical purpose.