Eddy Current Calculation of a High-Speed Slotted Machine With Halbach Magnetization at No-Load Condition

Abstract

The eddy current and the eddy current loss in permanent magnets (PMs) are important factors in high-speed machine design and performance prediction. The eddy current loss is related to the magnetic field, the shape of magnets, and rotating speed. In this article, the eddy current is analytically calculated with a 2-D method in a high-speed machine with the Halbach magnetization. This analytical method calculates the eddy current with two parts: one part is induced by the instantaneous radial flux density and the other part is induced by instantaneous tangential flux density. The instantaneous radial and tangential flux densities are varying in the PM when the rotor rotates. The flux density in the PM is calculated by the 2-D complex relative permeance method with the SC-Toolbox aid. When the slotted machine operated at no-load condition, the eddy current is analytically calculated in this article based on the instantaneous flux density, and the eddy current distribution in the magnet is compared with the finite-element method (FEM) solutions, the comparison shows that the 2-D analytical method is an effective method for the eddy current and eddy current loss calculation. In the slotted machine with the Halbach magnetization, the eddy current loss increases with the arc angle of the main segment magnet increases, the eddy current loss increases fast at high speeds and cannot be ignored, but Halbach magnetization can reduce it in the high-speed machine as long as the magnetization parameters are chosen properly.