Determination of winding inductances in ferrite type permanent magnet electric machinery by finite elements

A key design factor in ferrite type permanent magnet machines is the accurate knowledge of the values of machine winding inductances during the design stage. In the present paper, a method which is based on perturbation of the energy stored in the magnetic field, and on numerical models of simulation of such permanent magnets is used in calculating machine inductances. The effect of change in the values of these winding inductances with magnet position throughout the cycle of operation of such machines is given. These inductances also include the apparent and incremental values, whose definition is directly related to the choice of apparent or incremental reluctivities in the energy perturbation process. Results of application of this method to the calculation of inductances in a 15 hp 6-pole ferrite type electronically operated permanent magnet machine are given. These calculated values of inductances are in good agreement with the measured values.