New methods of measuring inductance of doubly salient permanent magnet motors

The inductance characteristic of doubly salient permanent magnet (DSPM) motors is the basis of design, analysis, and control of the motor. Due to the nonlinearity and doubly salient structure of the motor, this characteristic is a function of not only the rotor position, but also the strengthening and weakening actions of the armature flux to the permanent magnet (PM) flux, which makes the measurement of inductance difficult. This article proposes new methods for the measurement of the motor inductance for any rotor positions and level of excitation. The methods are applied to the two newly proposed DSPM motors and the results are compared with those obtained by finite element analysis, It is shown that the proposed peak value method can correctly reflect the influence of the strengthening and weakening actions of the armature flux to the PM flux on the inductance of DSPM motors.