Analytical analysis of sleeve permeability for output performance of high speed permanent magnet generators driven by micro gas turbines

An alloy sleeve is often used to prevent the damage to rotor magnets caused by the large rotational centrifugal forces within a high speed permanent magnet generator (HSPMG). It should be thick enough to satisfy the mechanical strength needed. The generator main reluctance mainly focuses on the rotor sleeve, so sleeve permeability has much influence on the magnetic circuit and generator performance. Since a finite element simulation for every machine is time consuming and complicated, a simple analytical model of general surface-mounted permanent magnet machines has been established within this paper. Additionally, an analytical method is also given in full, so that optimal sleeve permeability can be obtained for a set of parameters for a given machine. In order to accurately establish the variation of the pole-to-pole leakage flux in the air gap and rotor sleeve of the generator with different permeability sleeves, an iterative method is proposed. The leakage flux, main flux, magnet performance and their relationships with the generator have been studied further, and the influence mechanism of sleeve permeability on the generator performance has been determined. Based on the research of the above influence factors, the optimal sleeve permeability is obtained by using the analytical method. Comparing the results of the analytical method and finite element method, they are in close agreement; hence the rotor sleeve with optimal permeability can improve the generator performance. (C) 2016 Elsevier Inc. All rights reserved.