Design of external rotor switched flux memory machine with hybrid magnets
ISSN: 0332-1649
Article publication date: 7 March 2016
Abstract
Purpose
The purpose of this paper is to propose the design concepts of external rotor switched flux hybrid magnet memory machine (SFHMMM) to further increase the torque capability while keeping the merits of internal rotor SFHMMM, such as adjustable back-EMF, and good flux weakening performance, etc.
Design/methodology/approach
The torque enhancing principle of external rotor SFHMMM, and the design considerations such as feasible stator and rotor pole numbers (Ns/Nr ) are discussed by equations. Then, the performances such as back-EMF, dq-axis inductances, torque and flux weakening performances are calculated and compared with the aid of finite element analysis software.
Findings
The external rotor SFHMMMs have obviously larger torque capabilities compared with the internal rotor ones under the same copper loss and machine size. The main reason is that the external SFHMMs could fully utilize the inner space of stator, which offers higher slot area, larger split ratio and consequently the higher average torque. For the external rotor machines with larger rotor pole number Nr , the back-EMF adjust ratio as well as the maxim torque are better. However, leakage flux and losses also increase with Nr due to limited machine size and higher operation frequency. Considering torque capability and flux weakening performance (efficiency map), the external SFHMMM with Nr =2Ns +1, e.g. 6/13 Ns/Nr stator/rotor pole machine, is the optimal choice.
Originality/value
This paper introduces the design concept and design considerations of external SFHMMM for the first time. The proposed machine could be a competent candidate for direct-drive electric vehicle applications.
Keywords
Citation
Wu, D., Zhu, Z.Q. and Liu, X. (2016), "Design of external rotor switched flux memory machine with hybrid magnets", COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, Vol. 35 No. 2, pp. 507-524. https://doi.org/10.1108/COMPEL-03-2015-0132
Publisher
:Emerald Group Publishing Limited
Copyright © 2016, Emerald Group Publishing Limited