Open-Circuit Field Prediction of Interior Permanent-Magnet Motor Using Hybrid Field Model Accounting for Saturation

A hybrid field model (HFM) based on the combination of magnetic equivalent circuit (MEC) and exact conformal mapping (ECM) is developed to calculate the open-circuit field of interior permanent-magnet (IPM) motor. In the proposed HFM, the IPM and iron saturations are transformed into equivalent current on the rotor surface and stator bore. ECM can calculate the air-gap field analytically using the equivalent current. Once the air-gap field is obtained, the MEC in the iron region can be solved and gives the new value of equivalent current, which forms a calculation loop. Hence, iterative solving process is required to determine the equivalent current and iron permeability in the rotor and stator. In order to verify the proposed model, both finite-element (FE) analysis and experiment are performed on IPM motors with V-type rotor and conventional “-” type rotor. Their results demonstrate the high accuracy of HFM.