第四章电力电子技术与电力传动

《第四章电力电子技术与电力传动》由会员分享，可在线阅读，更多相关《第四章电力电子技术与电力传动（147页珍藏版）》请在金锄头文库上搜索。

1、 ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论1第四章第四章 电力电子技术与电力传动电力电子技术与电力传动 1电力电子技术的作用电力电子技术的作用2电力电子技术的特点电力电子技术的特点3电力电子技术的研究内容电力电子技术的研究内容4电力电子技术的主要应用领域电力电子技术的主要应用领域5电力电子技术的发展方向电力电子技术的发展方向6电力传动概况电力传动概况 ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论21电力电子技术的作用电力电子技术的作用 ANHUI UNIVERSITY OF TECHNOLOGY

2、电气工程专业导论电气工程专业导论3交流电源交流电源（交流发电机）（交流发电机）直流电源（太直流电源（太阳能电池等）阳能电池等）交流交流/直流直流直流直流/交流交流直流输电直流输电直流直流/交流交流电力系统电力系统一般工业系统一般工业系统（钢铁等）（钢铁等）交通运输交通运输（电气化铁道、电（电气化铁道、电动汽车）动汽车）家用电器产品家用电器产品（逆变器空调等）（逆变器空调等）其它（如其它（如UPS)电力电子技术的应用领域电力电子技术的应用领域 ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论41电力电子技术的作用（续）电力电子技术的作用（续） p当今世

3、界电力能源的使用约占总能源的当今世界电力能源的使用约占总能源的当今世界电力能源的使用约占总能源的当今世界电力能源的使用约占总能源的40%40%。而电。而电。而电。而电能中有能中有能中有能中有40%40%需要经过电力电子设备的变换才能被使用。需要经过电力电子设备的变换才能被使用。需要经过电力电子设备的变换才能被使用。需要经过电力电子设备的变换才能被使用。pIEEEIEEE给出电力电子技术的定义：给出电力电子技术的定义：给出电力电子技术的定义：给出电力电子技术的定义： Power electronics is the technology associated with the efficient

4、 conversion, control and conditioning of electric power by static means from its available input form into the desired electrical output form. p它是电子工程、电力工程和控制工程相结合的一门它是电子工程、电力工程和控制工程相结合的一门它是电子工程、电力工程和控制工程相结合的一门它是电子工程、电力工程和控制工程相结合的一门技术，以控制理论为基础、以微电子器件或计算机为技术，以控制理论为基础、以微电子器件或计算机为技术，以控制理论为基础、以微电子器件或计算机

5、为技术，以控制理论为基础、以微电子器件或计算机为工具、以电子开关器件为执行机构实现对电能的有效工具、以电子开关器件为执行机构实现对电能的有效工具、以电子开关器件为执行机构实现对电能的有效工具、以电子开关器件为执行机构实现对电能的有效变换。变换。变换。变换。 ANHUI UNIVERSITY OF TECHNOLOGYp更普遍的定义：电力电子学是一门利用电力电子器件更普遍的定义：电力电子学是一门利用电力电子器件更普遍的定义：电力电子学是一门利用电力电子器件更普遍的定义：电力电子学是一门利用电力电子器件对电能进行控制和转换的学科。对电能进行控制和转换的学科。对电能进行控制和转换的学科。对电能进行控

6、制和转换的学科。电力电子技术的根电力电子技术的根电力电子技术的根电力电子技术的根本特性本特性本特性本特性节约能源。节约能源。节约能源。节约能源。电气工程专业导论电气工程专业导论51电力电子技术的作用（续）电力电子技术的作用（续） ANHUI UNIVERSITY OF TECHNOLOGY传统电力技术如何将交流电变为直流电？基本原理缺点电气工程专业导论电气工程专业导论61电力电子技术的作用（续）电力电子技术的作用（续）例例1 ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论71电力电子技术的作用（续）电力电子技术的作用（续）例例2 如何用电力电子开关

7、器件实现电能的变换？DC/DC直流降压电路 ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论8方案一方案一: 电阻降压电阻降压 ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论9方案二方案二: 串联晶体管串联晶体管 ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论10方案三方案三:串联单刀双掷开关串联单刀双掷开关,理想开关理想开关,无损耗无损耗串联串联LC, 滤出谐波滤出谐波, 滤波器的截止频率滤波器的截止频率 如何用一系列等幅不等宽的脉冲等幅不等宽的脉冲来代替一

8、个正弦半波SPWM 波Ou（C）ttOut91 ANHUI UNIVERSITY OF TECHNOLOGY直流电机数学模型的性质直流电机数学模型的性质 直流电机的磁通由励磁绕组产生，可以在电枢合上电源以前建立起来而不参与系统的动态过程（弱磁调速时除外），因此它的动态数学模型只是一个单输入和单输出系统。电气工程专业导论电气工程专业导论92交流电机的矢量控制交流电机的矢量控制直流电机直流电机模型模型Udn ANHUI UNIVERSITY OF TECHNOLOGY二极直流电机的物理模型dqFACifiaic励磁绕组电枢绕组补偿绕组 ANHUI UNIVERSITY OF TECHNOLOGYl

9、交流电机是多变量、强耦合的模型结构交流电机是多变量、强耦合的模型结构 由于这些原因，异步电机是一个多变量（多输入多输出）系统，而电压（电流）、频率、磁通、转速之间又互相都有影响，所以是强耦合的多变量系统，可以先用右图来定性地表示。电气工程专业导论电气工程专业导论94A1A2Us1(Is) 异步电机的多变量、强耦合模型结构 ANHUI UNIVERSITY OF TECHNOLOGY交流电机绕组的等效物理模型ABCABCiAiBiCF1a）三相交流绕组 ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论96 ANHUI UNIVERSITY OF TEC

10、HNOLOGY电气工程专业导论电气工程专业导论97 基本思想基本思想ABC坐标系 坐标系dq坐标系3/2变换C2s/2r以产生同样的旋转磁动势为准则，在三相坐标系上的定子交流电流 iA、 iB 、iC ，通过三相/两相变换可以等效成两相静止坐标系上的交流电流 i、i ，再通过同步旋转变换，可以等效成同步旋转坐标系上的直流电流 im 和 it 。 ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论98如果观察者站到铁心上与坐标系一起旋转，他所看到的便是一台直流电机，可以控制使交流电机的转子总磁通 r 就是等效直流电机的磁通，则M绕组相当于直流电机的励磁绕

11、组，im 相当于励磁电流，T 绕组相当于伪静止的电枢绕组，it 相当于与转矩成正比的电枢电流。 ANHUI UNIVERSITY OF TECHNOLOGY旋转的直流绕组与等效直流电机模型1FMTimitMT ANHUI UNIVERSITY OF TECHNOLOGY ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论101异步电动机的坐标变换结构图3/2三相/两相变换; VR同步旋转变换; M轴与轴（A轴）的夹角 3/2VR 等效直流等效直流电动机模型电动机模型ABC iAiBiCitimii异步电动机异步电动机 异步电机的坐标变换结构图 ANHU

12、I UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论102既然异步电机经过坐标变换可以等效成直流电机，那么，模仿直流电机的控制策略，得到直流电机的控制量，经过相应的坐标反变换，就能够控制异步电机了。 由于进行坐标变换的是电流（代表磁动势）的空间矢量，所以这样通过坐标变换实现的控制系统就叫作矢量控制系统（Vector Control System），控制系统的原理结构如下图所示。 ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论103 矢量控制系统原理结构图 控制器控制器VR-12/3电流控制电流控制变频器变频器3/2V

13、R等效直流电等效直流电动机模型动机模型+i*mi*t 1i*i*i*Ai*Bi*CiAiBiCiiimit反馈信号异步电动机给定信号 矢量控制系统原理结构图 ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论104在设计矢量控制系统时，可以认为，在控制器后面引入的反旋转变换器VR-1与电机内部的旋转变换环节VR抵消，2/3变换器与电机内部的3/2变换环节抵消，如果再忽略变频器中可能产生的滞后，则上图中虚线框内的部分可以完全删去，剩下的就是直流调速系统了。 ANHUI UNIVERSITY OF TECHNOLOGY 设计控制器时省略后的部分设计控制器时

14、省略后的部分电气工程专业导论电气工程专业导论105控制器控制器VR-12/3电流控制电流控制变频器变频器3/2VR等效直流等效直流电机模型电机模型+i*mi*t 1i*1i*1i*Ai*Bi*CiAiBiCiiimit反馈信号异步电动机给定信号 ANHUI UNIVERSITY OF TECHNOLOGY可以想象，这样的矢量控制交流变压变频调速系统在静、动态性能上完全能够与直流调速系统相媲美。电气工程专业导论电气工程专业导论106 ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论1073 3 3 3、特殊电机传动、特殊电机传动、特殊电机传动、特殊电机

15、传动 永磁无刷直流电机（永磁无刷直流电机（永磁无刷直流电机（永磁无刷直流电机（PMBLDCMPMBLDCMPMBLDCMPMBLDCM）图4-36 结构及定子三相绕组波形 ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论108 三相永磁同步电机（三相永磁同步电机（三相永磁同步电机（三相永磁同步电机（PMSMPMSMPMSMPMSM）图4-37 结构及定子绕组波形PMBLDCMPMBLDCM 与与PMSMPMSM的区别：的区别：的区别：的区别：（1 1）正反直流电）正反直流电）正反直流电）正反直流电 VS VS 正弦交流电正弦交流电正弦交流电正弦交流电

16、（2 2 2 2）转子位置分次检测）转子位置分次检测）转子位置分次检测）转子位置分次检测 VS VS 连续实时检测连续实时检测连续实时检测连续实时检测 ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论109 同步磁阻电机（同步磁阻电机（同步磁阻电机（同步磁阻电机（SyncrelSyncrelSyncrelSyncrel）图4-38 开关磁阻电机结构与控制 开关磁阻电机开关磁阻电机开关磁阻电机开关磁阻电机 (SRM)(SRM)(SRM)(SRM)磁阻：磁阻：磁阻：磁阻：解决永磁体的失磁问题解决永磁体的失磁问题解决永磁体的失磁问题解决永磁体的失磁问题同步

17、磁阻电机与开关磁阻电机区别：同步磁阻电机与开关磁阻电机区别：同步磁阻电机与开关磁阻电机区别：同步磁阻电机与开关磁阻电机区别： 定转子之间气隙磁场正弦分布定转子之间气隙磁场正弦分布定转子之间气隙磁场正弦分布定转子之间气隙磁场正弦分布 VS VS 非正弦分布非正弦分布非正弦分布非正弦分布 ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论110谢谢大家！ ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论1114.14.1 Role of Power Electronics Role of Power Electr

18、onics4.24.2 Features of Power Electronics Features of Power Electronics4.34.3 Research Topics on Power Electronics Research Topics on Power Electronics4.44.4 Main Applications of Power Electronics Main Applications of Power Electronics4.54.5 Development Trends of Power Electronics Development Trends

19、 of Power Electronics4.64.6 General introduction to Electric Drives General introduction to Electric DrivesChapter 4 Power Electronics and Electric Drives ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论112p There is nearly 40% of the power converted by power electronic converters, while electric powe

20、r accounts for about 40% in world energy use.pp Power electronics defined by IEEE as follows:Power electronics (PE) is the technology associated with the efficient conversion, control and conditioning of electric power by static means from its available input form into the desired electrical output

21、form. pp In a word，its a technology that convert a raw form of power source to a desired form by using electronic device as the switch, that is, power conversion.pp Combination of electronics, power, and control, the power electronics deals with efficient power conversion based on control theory, co

22、mputer tools, and electronic switches.4.14.1 Role of Power ElectronicsRole of Power Electronics ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论113Basic Block Diagram of Power Electronic circuit：power inpower in power outpower out control control LoadLoad converter converter ANHUI UNIVERSITY OF TECHNO

23、LOGY电气工程专业导论电气工程专业导论114 12kV/1.5kA, thyristor ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论115Controlled power switches ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论116160Mvar/42kV Static Var Generator, Norway ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论1174.2 Features of Power Electronics4.2 Fe

24、atures of Power ElectronicspInterstitial to three areas of electrical engineering (Power, Electronics, Control) is power electronics, a novel interdisciplinary.pFeatures: 1. 1. Power controlled by electronic technology; widely including basic theory, professional theory and technology, such as: soli

25、d state physics, electromagnetism, circuit; power systems, electronics, heat transfer control systems, motor & drives, communication, signal processing, microelectronics; electromagnetic measurement, computer simulation and CAD;2. 2. Energy transfer by A/D, D/A technology;3. 3. interdisciplinary syn

26、thesis. ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论1184.3 Research Topics on Power Electronics4.3 Research Topics on Power Electronics Power semiconductor devicesConverter topology designControl and regulationEnergy storage devicesCircuits packing and manufacturingElectromagnetic Interference and

27、 Compatibility ( EMI, EMC )Motor drivePower quality ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论119 Diode, Thyristor, GTO, VDMOS, BJT, IGBT, IGCT and their circuit symbols.Diode1. Power semiconductor devices (the core of power electronics) ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论120Thyristor

28、 ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论121GTO (gate-turn-off thyristor) ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论122VDMOS (Vertical Double-diffused MOSFET ) ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论123abBJT (Power Bipolar Junction Transistor)Also called GTR (Giant Transistor) ANHUI

29、 UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论124IGBT (Insulated Gate Bipolar Transistor) ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论125IGCT (Intergrated Gate Commutated Thyristor) ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论126pFour types of converters categorized by power conversion forms： AC/DC c

30、onverterRectifier； DC/DC converterDC chopper； DC/AC converterInverter； AC/AC converterPower controller, Cycloconverter；pA good design of the converter includes several aspects such as: Function Factor, EMC, Heat Sink and Structure Compatibility.InputOutput2. Converter topology design ANHUI UNIVERSIT

31、Y OF TECHNOLOGY电气工程专业导论电气工程专业导论127Computer control and regulation3. Control and RegulationAll power electronicapplications contain control and regulation: Static power conversion and control;Static power supply;Motion control, etc. ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论1284. Energy storage c

32、omponent in power electronicsppIncluding: magnetic element and Including: magnetic element and capacitor.capacitor.ppThere are more kinds of magnetic There are more kinds of magnetic materials in power electronic technology, materials in power electronic technology, such as soft magnetic alloy (Fe-N

33、i alloy, such as soft magnetic alloy (Fe-Ni alloy, Fe-Al alloy, and Fe-Co-V alloy, etc), Fe-Al alloy, and Fe-Co-V alloy, etc), ferrite (Mn-Zn ferrite, Mg-Zn ferrite, ferrite (Mn-Zn ferrite, Mg-Zn ferrite, etc), new amorphous and etc), new amorphous and microcrystalline soft magnetic material microcr

34、ystalline soft magnetic material (Fe-based amorphous, Co-based (Fe-based amorphous, Co-based amorphous, etc). amorphous, etc). ppCapacitor is a energy storage and filter Capacitor is a energy storage and filter component paired with magnetic component paired with magnetic ponent.ppPlanar transformer

35、 in Planar transformer in PCBPCB ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论1295. Packaging and manufacturing of electronic circuitppThe packaging technique in power semiconductor devices includes The packaging technique in power semiconductor devices includes material, manufacturing process, rad

36、iating management, and layout material, manufacturing process, radiating management, and layout optimization problem corresponding with electrical characteristics of optimization problem corresponding with electrical characteristics of devices.devices. ppIntelligent IGBT module packagingIntelligent

37、IGBT module packaging ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论1306. EMI and EMCppPower electronics technology operates in Power electronics technology operates in du/dt and du/dt and di/dt. Obviously it di/dt. Obviously it is a big EMI source when the power electronics system is working;is a b

38、ig EMI source when the power electronics system is working;ppEMI and EMC are important research content in power electronics EMI and EMC are important research content in power electronics technology.technology.ppThe power electronics equipment is in EMI experimentThe power electronics equipment is

39、in EMI experiment. . ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论1317. Motor controlppElectric drive system can also be called as power drive system and Electric drive system can also be called as power drive system and motor speed control system. motor speed control system. Including: speed contr

40、ol drive for process, Including: speed control drive for process, speed control drive for speed control drive for energy saving, traction speed control drive and accurate, special speed energy saving, traction speed control drive and accurate, special speed control drive.control drive.ppAC motor and

41、 vector control speed regulation AC motor and vector control speed regulation frequency inverterfrequency inverter ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论1328. Power stability and power quality controlppIncludes: voltage quality, Includes: voltage quality, current quality, power supply curren

42、t quality, power supply quality and power quality and power consumption quality.consumption quality.ppFACTS device: static var FACTS device: static var compensator (SVC), thyristor-compensator (SVC), thyristor-controlled series switched controlled series switched capacitor (TSSC), thyristor-capacito

43、r (TSSC), thyristor-controlled series capacitor, controlled series capacitor, unified power flow controller unified power flow controller (UPFC), etc.(UPFC), etc.ppCustomer power technology: Customer power technology: APF, DVR, SVC, SSCB, etc.APF, DVR, SVC, SSCB, etc.ppPower quality control diagram

44、using Power quality control diagram using SVC, DVR, and APF.SVC, DVR, and APF. ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论133ppMain application areasMain application areas: :Source design;Source design;Motor drive;Motor drive;Power system;Power system;Automobile industry;Automobile industry;Green

45、 lighting;Green lighting;New energy exploitation.New energy exploitation.4.4 Main Applications of Power Electronics Technology4.4 Main Applications of Power Electronics Technology ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论134ppIntegrationIntegrationppModulationModulationppIntellectualizationInte

46、llectualizationppHigh frequencyHigh frequencyppConstant improvement of device efficiencyConstant improvement of device efficiencyppContinuously extended voltage application rangeContinuously extended voltage application range4.5 Development Trend of 4.5 Development Trend of Power Electronics Technol

47、ogy Power Electronics Technology ANHUI UNIVERSITY OF TECHNOLOGYp DC motor and AC motorp Regulating the motor torque and speed to adapt to the loads by using power electronic converters电气工程专业导论电气工程专业导论1354.6 General introduction to Electric Drives4.6 General introduction to Electric DrivesTypical ele

48、ctric drives system Power sourcePE converterMotorLoadInstructions and monitors Driver ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论1361. DC motor drives1. DC motor drives Te：electromagnetic torqueCT：torque constantCe：EMF constant：main magnetic fluxIa：armature currentEa：armature windings back-EMF：mo

49、tor speed, rad/sUa：power supplyRa：resistance of the motors armature windingsFrom (4-1), (4-2)From (4-1), (4-2) formulas, motor torque and speed could formulas, motor torque and speed could be regulated by armature current or power supply of the be regulated by armature current or power supply of the

50、 motor.motor.(4-1)(4-2) ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论137 Voltage control Voltage control AC/DC rectifier： Full-wave rectifier Phase controlled rectifier PWM rectifier Output voltage waveforms ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论138DC/DC chopper:(a)(b)Underground train DC/D

51、C chopper (a) Topology (b) Waveform Ua ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论1392. AC motor drives2. AC motor drives DC/AC inverter motor drive ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论140 Single phase inverterSingle phase inverter SPWM SPWM Topology and waveforms ANHUI UNIVERSITY OF TE

52、CHNOLOGY电气工程专业导论电气工程专业导论141 Three-phase inverterThree-phase inverterTopology and waveforms ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论142 Pulse Width ModulationPulse Width Modulation Principle:Principle: Nearly equal effects generated when different shapes but same areas narrow pulses were applie

53、d to a inertia element. PWM theory ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论143Different modulation depths Effects on motorsEffects on motors：（：（：（：（harmonicsharmonics） (1) du/dt(1) du/dt (2) Common mode voltage in motor neutral point(2) Common mode voltage in motor neutral point ANHUI UNIVERSI

54、TY OF TECHNOLOGY电气工程专业导论电气工程专业导论1443. Special motor drives3. Special motor drives P Permanent magnet brushless DC motor (PMBLDCM)ermanent magnet brushless DC motor (PMBLDCM)Structure and stator armature waveforms ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论145 Three phase permanent magnet synchron

55、ous motor (PMSM)Three phase permanent magnet synchronous motor (PMSM)Structure and stator armature waveformsPMBLDCMPMBLDCM and and PMSM differences:PMSM differences:(1) Positive and negative DC (1) Positive and negative DC VS VS Sinusoidal AC, power supplySinusoidal AC, power supply(2) Discontinuous

56、 detection (2) Discontinuous detection VS VS Continuous detection, rotor positionContinuous detection, rotor position ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论146 Synchronous reluctance motorSynchronous reluctance motorSwitched reluctance motor structure and control circuit Switched reluctance

57、motorSwitched reluctance motorReluctanceReluctance：Permanent magnet loss of excitation problemPermanent magnet loss of excitation problemDifferencesDifferences： Sinusoidal air-gap magnetic fieldSinusoidal air-gap magnetic field VS VS Non-sinusoidalNon-sinusoidal ANHUI UNIVERSITY OF TECHNOLOGY电气工程专业导论电气工程专业导论147Thanks！