Junqiang Zheng

Design and Analysis of a Linear Permanent- Magnet Vernier Machine With Improved Force Density

This paper proposes a novel linear permanent-magnet (PM) vernier machine, which offers high force density, high efficiency, simple structure, and low cost. The novelty of the proposed machine is substantiated by integrating appropriate magnetization directions of PMs in the armature core. First, the structure and the operation principle of the proposed machine are descried. The machine is subsequently designed for a given set of specifications and its electromagnetic performances are analyzed by time-stepped transient finite-element method. An analytical equation is derived for evaluation of the thrust force ripple. Finally, experiments on a prototype of the proposed machine are carried out for validation.

Reduction of Tooth Harmonic in Fractional-Slot Concentrated-Winding Permanent-Magnet Machines Using New Stator Design

Fractional-slot concentrated windings (FSCWs) are characterized with many advantages. However, their magnetic fields have rich space harmonics. These harmonics, especially tooth harmonics, have negative effect on machine performances. This paper proposes a new method to reduce the tooth harmonics in FSCW permanent-magnet (PM) machine, in which the magnetic distribution in air-gap will be affected by winding span radian. Also, a new stator structure is designed on the method. By using the new stator design, each order tooth harmonic can be reduced significantly and the working harmonic can also be increased slightly. Simultaneously, the unbalanced radial magnetic force can be significantly weakened. The basic principle of tooth harmonic reduction method can be analyzed by using the stator structure of the FSCW machine with single layer windings. Then, a three phase 18-slot/16-pole FSCW machine with double layer windings is newly designed, which can effectively weaken the tooth harmonic components of FSCW machines. It is shown that, under the fixed electrical and geometrical constrains, the designed FSCW machine has better performances, such as loss, vibration and noise, than the conventional ones.

Comparison of coaxial magnetic gears with parallel and series magnetic circuits

This paper quantitatively compares two coaxial magnetic gears (CMGs) with parallel magnetic circuit and series magnetic circuit, which are artfully integrated into a permanent magnet (PM) brushless DC motor. By using the finite-element method, the performances of both CMGs are compared and evaluated. Analysis results show that the CMG series magnetic circuit can offer higher pull-out torque and back-EMF than the CMG parallel magnetic circuit, while the CMG parallel magnetic circuit has lower PM eddy current loss, iron losses and lower distortion of back-EMF.

Design and comparison of interior permanent-magnet machines for hybrid electric vehicles

This paper is to compare five different rotor topologies of distributed winding interior permanent-magnet (IPM) machine for electric vehicles. Their characteristics, which include back-electromotive force, torque, overload capability, flux weakening performance and d-q axis inductances are comparatively evaluated. This work gives some guidance and reference for machine designers who are interested in IPM machine selection for high-performance traction applications.

Normal force and vibration investigation of linear permanent-magnet vernier machine

Normal force is the dominant source of vibration in the linear permanent-magnet (LPM) machine. In order to investigate vibration of a new LPM vernier machine, normal pressure and their spatial harmonics are calculated by finite element method. Then, the natural vibration modes and transient displacement of the short mover is predicted. Finally, experimental result is given for verification. Results are instructive for design of a high precision and low vibration LPM machine.

Harmonic impact on rotor losses in fault-tolerant interior permanent-magnet machines

Fractional-slot permanent-magnet (FCSPM) machines offer several advantages, but they suffer from the high content of space harmonics in the air-gap magnetic motive force (MMF) distribution. The MMF space harmonic amplitude and frequency depend on the particular combination of numbers of slots and poles. Such harmonics induce losses in the rotor since they are not synchronous with the rotor speed. The aim of this paper is to analyze the MMF distribution in the air-gap and calculate the rotor eddy current loss for two fault-tolerant interior permanent-magnet (FT-IPM) machines. Meanwhile, the efficiency has been predicted at different operating conditions. Both machines are built for verification.