Determination of Maximum Electromagnetic Torque in PM Brushless Machines Having Two-Segment Halbach Array

This paper develops a 2-D field analytical model for predicting the magnetic field distribution and the corresponding electromagnetic performance in air- and iron-cored permanent magnet (PM) brushless machines having radially or parallel magnetized two-segment Halbach array. A simple equation is derived to directly predict the optimal magnet ratio for maximum electromagnetic torque, while the influence of pole-pair number and magnet thickness on the optimal magnet ratio is investigated for both air- and iron-cored machines. The analytical model is validated by finite-element analyses and also measurements on a prototype 12-slot/10-pole PM brushless machine.