Analysis of Air-Gap Field Modulation and Magnetic Gearing Effects in Switched Flux Permanent Magnet Machines

• Published in: IEEE transactions on magnetics Vol. 51; no. 5; pp. 1 - 12
• Main Authors: Wu, Z. Z., Zhu, Z. Q.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01-05-2015; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Air gaps; Armature; Design engineering; Flux switching; Harmonic analysis; Magnetic flux; magnetic gear; magnetic gearing effect; magnetically geared machine; Magnetism; Modulation; permanent magnet machines; Rotors; Stators; switched flux; modulation; switched flux (SF); permanent magnet (PM) machines; Flux switching; harmonic analysis; magnetic gearing effect; magnetic gear; magnetically geared machine
• ISSN: 0018-9464; 1941-0069
• DOI: 10.1109/TMAG.2015.2402201

In this paper, switched flux permanent magnet (SFPM) machines are analyzed from the perspective of the air-gap field harmonics. It is found that the modulation of the salient rotor to PM and armature reaction fields in SFPM machines is similar to that of the iron pieces to those fields in the magnetic gear and magnetically geared machine. The magnetic gearing effect is analyzed in SFPM machines with different stator/rotor pole combinations, winding configurations, and stator lamination segment types by a simple magnetomotive force-permeance model, and validated by finite-element (FE) analysis. Different from fractional-slot surface-mounted PM machines in which the working air-gap field harmonic generates 95% of the average electromagnetic torque, 95% of the average electromagnetic torque in SFPM machines having ps stator pole pairs and n r rotor poles are contributed by several dominating field harmonics, i.e., rotating ones with |kn r ± (2i - 1)p s | pole pair (k = 1, i = 1, 2, 3) and static ones with (2i - 1)ps pole pair (i = 1, 2, 3). The FE predicted average static torques in SFPM machines are validated by measurements on prototype machines.