Analytical Calculation of 3-D Rotor Eddy Current Loss in High-Speed Permanent Magnet Motors Considering the Multi-Layer Rotor Structure

This article presents an analytical method to calculate 3-D rotor eddy current loss (RECL) in high-speed permanent magnet motors (HSPMSMs) by correcting each harmonic loss component of 2-D RECL. First, a 3-D analytical model of a multi-layer rotor, accounting for the armature reaction field, is established based on the equivalent current sheet. The 3-D governing equation is derived in stationary coordinate, and stator current is periodically extended in the axial direction. The end factors for correcting each time-spatial harmonic RECL are derived as the ratio of the RECLs for infinite and finite rotor lengths. To account for the influence of slotting effect and the magnetic field induced by the permanent magnet (PM), 3-D RECL is obtained by correcting the series formed 2-D RECL calculated using an accurate subdomain model. The accuracy of the proposed method is then verified through finite element analysis (FEA) at different motor sizes and frequencies. Finally, a rotor-locked test is carried out on an HSPMSM prototype, validating the effectiveness of the proposed analytical method.