Rapid Flux Concentration Factor Determination for Halbach Array Based PM Rotors Using Composite FE Based Method

Abstract

Conventional empirical-formulae (CEF) based permanent magnet (PM) motor design employs the use of several assumptions in the form of magnetic material non-linearity, air-gap and magnet reluctances derived from assumed leakage factors leading to the incorrect estimation of air-gap flux densities. This problem is much more prevalent in various forms of hybrid PM magnetization topologies such as Halbach array based PM (HAPM) or Halbach array based consequent pole based PM (HACPPM) rotors. In order to improve the air-gap magnetic flux density estimation using the CEF design method, a flux density adjustment factor is proposed in this work, which utilizes a look-up table formed upon a reduced electromagnetic finite-element simulation search space to improve the accuracy of flux density estimation in both Halbach and Consequent-Halbach PM rotors using the flux concentration factor (FCF). First, the derivation of the FCF is introduced. Then the effectiveness of the FCF + CEF method is analyzed quantitatively, in comparison with conventional CEF and 2D-FE (electromagnetic) methods and performance is analyzed.