Analytical Magnetic Field Modeling of Slotless Permanent Magnet Synchronous Motors

In this paper an analytical model for predicting the open-circuit magnetic field distribution in the air gap of iron-cored internal rotor with radial magnetization of surface mounted magnet and a slotless stator is presented. The model is extended to the prediction of the armature reaction field, back-emf and instantaneous torque produced by the 3-phase stator windings with fractional or integer slot per pole and per phase of iron-cored internal rotor. Analytical model can be adapted also for any type of windings. The results are in closed forms and provide a basis for comparative studies between existing permanent magnet (PM) machines and searching for new PM machines topologies. Predicted armature reaction field distribution, back-emf and instantaneous torque can be validated by comparing with corresponding finite element calculations.