Computationally Efficient 3-D Eddy Current Loss Prediction in Magnets of Interior Permanent Magnet Machines

This paper proposes a computationally efficient method based on imaging technique, for accurate prediction of 3-D eddy current loss in the rotor magnets of interior permanent magnet (IPM) machines. The 2-D time-stepped finite-element analysis (FEA) is employed to generate the radial and the tangential 2-D magnetic field information within the magnet for the application of the 3-D imaging technique. The method is validated with 3-D time-stepped FEA for an 8 pole, 18 slot IPM machine evaluating its resistance limited magnet loss with the increase in axial and tangential segmentation. Magnet loss considering eddy current reaction at high frequencies is evaluated from the proposed method by employing the diffusion of the 2-D magnetic field variation along the axial plane. The loss associated with all the frequencies together in the armature currents is evaluated by considering each of the harmonics separately in the proposed method employing the frozen permeability to account for magnetic saturation. The results obtained are verified with 3-D FEA evaluating the magnet loss at fundamental, 10 and 20 kHz time harmonics in armature currents.