Permeance Distribution Function: a Powerful Tool to Analyze Electromagnetic Forces Induced by PWM Current Harmonics in Multiphase Surface Permanent-Magnet Motors

This article introduces a new method to analyze electromagnetic forces induced by pulsewidth modulation current harmonics in inverter-fed surface permanent-magnet motors. The concept of the permeance distribution function (PDF) is first introduced with its properties and relation to machine inductances fully explained. Utilizing the concept of PDFs, two methods are proposed to calculate the flux distribution on stator boundaries by armature currents and rotor permanent magnets, respectively. By superposing the stator flux distributions from both sources, the final stator electromagnetic force distribution is obtained. The method is validated by finite-element analysis, demonstrating good accuracy and very fast computation time.