Path permeance based analytical inductance model for IPMSM considering saturation and slot leakage

The magnetizing q-axis inductance of an optimally designed interior permanent magnet machine (IPM) exhibits a saturating behavior as the current excitation increases. This research work proposes an analytical method to study this behavior by expressing armature reaction as the product of stator MMF and flux path permeance function. The path permeance is a function of both the lamination geometry and the saturated conditions in steel regions. In slotted IPMs, the stator tooth conducts both the magnetizing flux and slot leakage flux, which superpose with each other to determine the saturation condition. This subsidiary phenomenon is investigated in detail using Ampere's law and flux continuity law. Two models are developed and applied to IPMs with single layer and double layer rotor topologies. The results are validated with FEA and a single variable optimization of slot dimensions is illustrated.