A electric vehicle, are assessed for the risk of partial irreversible demagnetization under various fault conditions. This paper describes a more accurate approach of demagnetization assessment based on 2-D transient finite-element analysis. It is shown that due to the presence of low-order space harmonics in the fractional-slot IPM machine, the demagnetization risks across all pole pairs are different. Compared with the distributed wound machine, the fraction-slot machine is less vulnerable to demagnetization due to relatively high winding inductance, although its demagnetized regions are not uniform in each pole. It is also shown that although the demagnetizing current of one 3-phase short-circuit (SC) is greater than that of 6-phase SC, the resultant demagnetization risk is lower than that of 6-phase SC in the fractional-slotmachine.Index Terms-Demagnetization, distributed winding, electric vehicle (EV), fractional-slot winding, permanent magnet (PM) machines, short-circuit (SC) faults.

This is a repository copy of An analytical method for predicting 3D eddy current loss in permanent magnet machines based on generalized image theory.

This paper assesses post demagnetization performance of Interior Permanent Magnet (IPM) AC machines by employing the more accurate recoil line approach based on 2-D transient finite element (FE) analysis. The method predicts continuous demagnetization of each magnet element undergoing partial demagnetization and evaluates the machine behavior after an event of short-circuit faults across its terminals. Along with the short-circuit faults, a failure in drive controller or position sensor which may lead to a reverse voltage across the machine terminals that can eventually be more fatal and can cause significant reduction in the performance due to high levels of demagnetization, is analyzed as the worst case scenario. The FE predicted post demagnetization performance is validated by experimental measurements in which a 6-phase Interior Permanent Magnet machine designed for EV traction is allowed to lose its synchronization with the inverter when forced to operate on a torque-speed envelope which is way beyond the drive voltage setting.

--This paper proposes a computationally efficient method, for accurate prediction of 3-dimensional (3D) high frequency eddy current loss in the rotor magnets of surface mounted permanent magnet machines employing the imaging method. 2D finite element analysis (FEA) is used to generate the information on radial and tangential 2D magnetic field variations (eddy current sources) within the magnet. The diffusion of eddy current sources along the axial plane of the magnet computed analytically is incorporated in the imaging method to establish the 3D eddy current source variations within the magnet. The modified method is validated with results from 3D time-stepped finite element analysis (FEA) for an 8-pole, 18-slot permanent magnet machine, evaluating its magnet loss considering axial and circumferential segmentation.Index Terms-Eddy current, finite element, permanent magnet machines.

This study proposes a computationally efficient analytical method, for accurate prediction of three-dimensional (3D) eddy current loss in the rotor magnets of surface mounted permanent magnet (SPM) machines considering slotting effect. Subdomain model incorporating stator tooth tips is employed to generate the information on radial and tangential time-derivatives of 2D magnetic field (eddy current sources) within the magnet. The distribution of the eddy current sources in 3D is established for the magnets by applying the eddy current boundary conditions and the Coulomb gauge imposed on the current vector potential. The 3D eddy current distributions in magnets are derived analytically by employing the method of variable separation and the total eddy current loss in the magnets are subsequently established. The method is validated by 3D time-stepped finite element analysis for 18-slot, 8-pole and 12-slot, 8-pole permanent magnet machines. The eddy current loss variations in the rotor magnets with axial and circumferential number of segmentations are studied. The reduction of magnet eddy current loss is investigated with respect to harmonic wavelength of the source components to suggest a suitable segmentation for the rotor magnets in SPM machines.