定子永磁型无刷电机综述

Overview of Stator-Permanent Magnet

Brushless Machines

Ming Cheng,Senior Member,IEEE,Wei Hua,Member,IEEE,Jianzhong Zhang,Member,IEEE,and

Wenxiang Zhao,Member,IEEE

Abstract—Permanent magnet(PM)brushless machines having magnets and windings in stator(the so-called stator-PM machines) have attracted more and more attention in the past decade due to its definite advantages of robust structure,high power density, high efficiency,etc.In this paper,an overview of the stator-PM ma-chine is presented,with particular emphasis on concepts,opera-tion principles,machine topologies,electromagnetic performance, and control strategies.Both brushless ac and dc operation modes are described.The key features of the machines,including the mer-its and drawbacks of the machines,are summarized.Moreover,the latest development of the machines is also discussed.

Index Terms—Doubly salient,flux reversal,flux switching, overview,stator-permanent magnet(PM).

I.I NTRODUCTION

W ITH THE significant achievements of permanent mag-net(PM)materials and power electronic devices,brush-less machines excited by PMs are developing dramatically. Generally speaking,there are a total of four types of PM machines which have magnets located on the rotor,and they are the following:1)surface mounted;2)inset;3)radial interior; and4)circumferential interior.It should be emphasized that all of the PM machines mentioned have magnets located on the rotor,and they are referred to as“rotor-PM machines”in this paper,which predominate in the industry applications due to outstanding advantages[1],[2].However,magnets usually need to be protected from the centrifugal force by employing a retaining sleeve,which is made of either stainless steel or nonmetallicfiber.Rotor temperature rise may be a problem due to poor thermal dissipation,which may cause irreversible demagnetization of magnets and may ultimately limit the power density of the machine.Recently,in contrast,a new type of PM

Manuscript received March21,2010;revised June28,2010,October1, 2010,and December21,2010;accepted February16,2011.Date of publication March7,2011;date of current version September7,2011.This work was supported in part by NSFC under Projects59507001,50377004,50337030, 50729702,50807007,60974060,and50907031;by the Specialized Research Fund for the Doctoral Program of Higher Education of China under Projects 20050286020,200802861038,and20090092110034;by the High Tech Re-search Program of Jiangsu Province,China,under Project BG2005035;and by the Aeronautical Science Foundation of China under Projects20080769007and 20100769004.

M.Cheng,W.Hua,and J.Zhang are with the School of Electrical Engineering,Southeast University,Nanjing210096,China(e-mail:mcheng@ ;huawei1978@;seuzjz@).

W.Zhao is with the School of Electrical and Information Engineering, Jiangsu University,Zhenjiang212013,China(e-mail:zwx@). Color versions of one or more of thefigures in this paper are available online at .

Digital Object Identifier

10.1109/TIE.2011.2123853

Fig.1.Stator-PM alternator in1955[3].

machine having magnets on the stator,nominated as stator-PM

machines,has re-emerged and has been developed,which can

overcome the problems suffered by the rotor-PM counterparts.

The purpose of this paper is to give an overview of the

stator-PM machines.Thus,the state-of-the art technology of

the stator-PM machines,including machine topologies,opera-

tion principles,characteristics,control strategies,torque ripple

minimization,and latest developments will be reviewed and

discussed.

II.C ONCEPTS OF S TATOR-PM M ACHINES

The idea of stator-PM machines can be traced back to1955

when Rauch and Johnson proposed probably thefirst stator-

PM topology,as shown in Fig.1[3],in which both the stator

tooth and rotor poles are salient so as to transfer thefluxes

created by the stator magnets from the stator to the rotor

across the air gap when the rotor poles face the stator teeth.

Thus,the polarities of theflux linked in the coils in the stator

reverse as the rotor aligns the alternative pair of stator teeth.

However,due to the limitation of the magnet property at that

time,the stator-PM machines were overwhelmed by wound-

field excitation machines,e.g.,synchronous and dc machines.

Another origin of the stator-PM machine can be found from

the well-known Law’s relay actuator shown in Fig.2[4].In

addition,the doubly salient structure employed in electrical

machines can also originate from an induction-type generator,

as shown in Fig.3[5],in which the stator assembly is a set of

pieces arranged in a cylinder laminated iron,with the armature

windings wound.The special geometry allows the variation of

the magnetflux that is linked into the“C”-shaped stator pole

pieces to induce electromotive force(EMF).

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