Design And Analysis Of Permanent Magnet Machines With Harmonic Injection

Nowadays,permanent magnet(PM)machines have been widely used in many fields,such as electric vehicles and aerospace.PM machines play a more and more important role.This is because some unique characteristics of PM machines,including high torque density,high efficiency,excellent dynamic performance and small weight,etc.high magnetic energy products have replaced the traditional excitation winding in PM machines.This not only eliminates the negative impact produced by the excitation winding,but also simplifies the mechanical structure of PM machines.Hence,operation reliability of machines is improved,whilst mechanical loss is reduced.Although PM machines have a series of advantages,it is still pretty challenging for some high-performance applications,such as power steering system,servo motor,wind power generator,speed and position control systems and so on.These applications require good output performances,i.e.,high average torques and low torque ripples.Therefore,how to improve the average torque and reduce the torque ripple always are the hot issues.This paper describes topologies and principles of PM machines,and the relative elements in terms of output properties are analyzed.Then,the shaping methods with harmonic injection are investigated to optimize output torque.A novel design method is proposed to obtain the optimal performance.It provides a new technology for optimization design of PM machines.Based on foregoing analyses,the content of this paper is given as follow:1.The principle of air gap flux density in surface-mounted PM(SPM)machines are analyzed using analytical method.The topologies of PM machines and the distributions of air-gap flux density are respectively described and derived.It provides a good foundation for theoretical explanations of harmonic shaping.2.This paper investigates the interior PM(IPM)and SPM machine with shaping methods,including the sinusoidal(SIN),the inverse cosine(ICS),the sinusoidal with third harmonic(SIN+3rd),and the inverse cosine with third harmonic(ICS+3rd).The electromagnetic performances of shaped machines are confirmed by FE method.3.In order to enlarge the application ranges,shaping variations of above four shaping methods are improved.Then,the shaping methods can be employed to the inner stator,inner rotor,outer stator and outer rotor of PM machines.Meanwhile,traditional brushless DC machines also can apply this method.4.The stator or rotor shaping named as single shaping,and the rotor and stator shaped at the same time termed as dual-shaping,are investigated.With the combinations of four shaping methods,eight topologies of dual-shaping will be produced.The performances of these topologies are analyzed.Then,some conclusions can be summarized.5.This paper proposes a new design method named feedback function design(FFD)for surface-mounted permanent magnet machines.The black box theory is introduced to the proposed method for torque improvement.Then,a system composed of input parameters,the black box and output parameters is established.Different input parameters have different output torques.As long as the input database is sufficient,the optimal performance of the objective machine is absolutely obtained.6.A prototype based on FFD is manufactured.The experimental platform is established.Good agreements are achieved between FE and measurement results.