Variable Magnetization Machine in Electrified Vehicle Application

This paper describes variable magnetization machines, which are capable of varying the magnetization state (MS) of permanent magnets during operation. A pulse current on the stator windings creates a magnetic field on the rotor; this can be used to manipulate the MS of the rotor magnets. Regulating the MS according to the machine operating condition can reduce machine losses. A proof‐of‐principle machine was designed and fabricated. A series of experiments was conducted to evaluate the torque–speed envelope and efficiency contours of the fabricated machine. A full‐scale machine was then designed with a modified magnetic circuit for application to an electric vehicle and evaluated using finite element analysis. A control strategy for the MS during machine operation is proposed, and the losses during a driving cycle with the strategy were evaluated.     

High-speed synchronous machines: A computer system for the study of the effect of rotor radial eccentricity on electromagnetic forces

The problem of the development of modern bearings (magnetic, gas, etc.) for high-speed machines with a wide range of capacities (from tens of kilowatts to megawatts) and rotational speeds (from 6000 to 60000 rpm) used in oil and gas production, robotics, space technology, and mini gas-turbine power plants is considered. The distribution of forces applied to the rotor shaft in different modes of operation is investigated including the case of shaft eccentricity. In operation, the eccentricity should not exceed 5%. A computer system is designed on the basis of the numerical method for field (2D) computation in the active part of the machine. The distribution of forces is analyzed taking into account the saturation of the magnetic circuit of the machine and the harmonic content of the mutual magnetic flux (flux in the gap). When calculating these forces in the no-load mode of operation, it was assumed that, in machines with permanent magnets, the mutual magnetic flux on the rotor is about 10–15% higher than under the rated load because of the demagnetization effect of the armature reaction. The mutual magnetic flux was specified depending on the type of rotor magnets. The computer system takes into account the relative position of the rotor poles relative to the stator field reaction under load (load angle Θ). It is also taken into account that, during use, the resulting mutual magnetic flux is distorted (compared to the no-load mode). As a result, a number of additional high harmonics appear in the gap, which affect the forces applied to the rotor shaft. Load angle Θ is calculated using graphical options of the simulation package by the iteration method. An algorithm for the implementation of this method is described. The distribution of the radial forces along the rotor shaft surface (differential parameter) and the total radial attraction force applied to the rotor shaft (integral parameter) are calculated for different values of eccentricity and different modes of operation of high-speed machines.     

Two-Dimensional Field Analysis of Cylindrical Machines with Permanent Magnet Excitation

The design of the magnetic circuit of permanent magnet machines differs from that of conventional wound field machines mainly due to the low magnetic permeability of the magnets. A two-dimensional field analysis is presented which takes the magnet leakage, the distribution of magnet MMF along its height, and the changing magnet width into consideration. The fundamental component of flux calculated by the model is compared with results obtained by finite element analysis for different magnet configurations covering a practical range of magnet dimensions. A comparison of machine performance predicted using this method with test results is also given.     

Basic principles and characteristics of hybrid excitation synchronous machine

Permanent magnet type synchronous machines have been widely used for industrial applications. It is commonly known that they are operated at high efficiency since no excitation input is required. However, it is difficult to control the air-gap magnetic flux, because the magnetic flux is determined by the property of the permanent magnet and approximately kept constant. On the other hand, synchronous machines with the field winding make it easy to control the air-gap magnetic flux. But the copper loss of the field winding becomes large at the rated load. In order to realize the magnetic flux control easily and improve the performance of the conventional synchronous machine, we propose a hybrid excitation type synchronous machine (HSY) with the permanent magnets and the field winding. Advantages of HSY are (1) it has no brushes (maintenance free), (2) required excitation input is small (high efficiency), (3) it is easy to get a sufficient magnetic flux control, and others. Therefore, HSY has a great possibility of use for various applications. In this paper, basic principles and characteristics of HSY are mainly discussed and made clear.     

表面-内置混合式永磁同步电机性能与转子参数影响

为研究表面-内置混合式永磁同步电机表面磁极和内置磁极的作用,采用有限元方法建立该电机仿真模型,通过对其空载特性和负载特性的分析可知该电机的空载特性受表面磁极影响较大,而其负载特性受内置磁极影响较大。进一步以表面-内置混合式永磁同步电机的转矩性能为参考指标,对转子表面磁极、内置磁极以及隔磁桥三部分的参数进行分析。结果表明改变表面磁极参数对改善气隙磁场,减小转矩波动有着较好的效果,而改变内置磁极参数对转矩波动影响较小,但对转矩幅值影响较大。此外受表面磁极的影响,内置磁极两端隔磁桥1处的漏磁随其宽度变化较小,因此可适当放宽隔磁桥1处的宽度,以改善电机转子机械强度,提高电机整体性能。     

永磁外转子爪极发电机的漏磁计算

针对具有特殊结构的永磁外转子爪极发电机复杂的漏磁计算问题,在对电机的结构、材料、特点以及运行机理进行分析的基础上,首先采用常规的磁路分析方法,建立了电机的等效磁路模型,推导出各部分的漏磁阻及漏磁通计算公式并进行了相应的分析;然后利用有限元分析方法建立了电机的三维电磁场分析仿真模型,并对电机的各部分漏磁进一步加以分析计算;最后对磁路和有限元两种方法的计算结果加以对比研究,用相对准确的有限元计算结果来修正磁路计算法中磁阻公式的系数;达到了运用简单磁路公式快速准确分析该种复杂结构电机漏磁的目的。     

新型混合励磁同步电机的数学模型与等效分析

为改善高速永磁电机磁场调节困难的问题,提出一种新型混合励磁电机,转子上既有永磁极又有铁心极,磁路呈现典型的径向、周向和轴向三维特性,难以直接用解析法求取电感参数。根据新型混合励磁电机的磁路特点,提出一种等效分析方法,将复杂磁路的混合励磁电机等效为三种二维磁路电机轴向并列叠加。为了提高新型混合励磁电机电磁设计与性能分析的效率,推导了其数学模型与电感参数表达式。对一台10 k W混合励磁原理样机进行了有限元分析与实验研究,结果验证了所提数学模型与等效分析方法的正确性,为该类电机的设计和优化提供了理论支撑。     

Performance Evaluation of an Axial‐Type Magnetic‐Geared Motor

This paper first proposes an axial‐type magnetic‐geared motor that uses permanent magnets only in the high‐speed rotor. The operating principle of this motor is described and the torque–speed characteristics are computed by using three‐dimensional finite element method analysis. In order to increase the torque density, a novel axial‐type magnetic‐geared motor with permanent magnets on the high‐speed rotor and stator is also proposed. The torque–speed characteristics are compared to the original model with permanent magnets only on the high‐speed rotor. Finally, the computed torque–speed characteristics are verified against measurements on a prototype.     

A study of magnetic rotor systems of high-speed electromechanical energy converters

This paper presents the results of a study of magnetic rotor systems of high-speed electromechanical energy converters in the Ansoft Maxwell software package, followed by experimental test. Two magnetic systems were considered: with semicircular and cylindrical permanent magnets. It has been found out that the system with semicircular permanent magnets makes it possible to create an electromechanical energy converter with less dense current in the windings and lower losses at identical weight and dimensions. Moreover, the rotor magnet system with semicircular permanent magnets reduces mechanical stresses in the shrouding rotor shell and, correspondingly, its mechanical expansions during operation. We have considered a case of selecting the number of terminal pairs of high-speed electrical machines with permanent magnets, which required preliminary calculations of losses in the magnetic circuit with aimed parameters for different numbers of terminals.     

Cogging Torque Characteristics of a Magnetic‐Geared Motor

This paper describes the cogging torque characteristics of a magnetic‐geared motor with permanent magnets only on the high‐speed rotor. The operational principle, which is different from that of the magnetic‐geared motor with permanent magnets on the high‐speed rotor and stator, is described. The torque characteristics, especially the order of the cogging torque, are mathematically formulated and verified by conducting 3D finite element analysis and carrying out measurements on a prototype. A novel cogging torque reduction method is proposed and verified as well.     

双凸极变速永磁电机的变结构等效磁路模型

建立了双凸极变速永磁电机的变结构等效磁路模型,推导了气隙比磁导计算公式,通过求解所建立的非线性等效磁路方程,以计算电机的静态特性,计算中计及铁磁材料的非线性以及永磁磁场与电枢反应磁场之间经影响。通过引入适当的修正系数,使计算结果与有限元结果吻合。以新提出的12／8极双凸极永磁电机为算例,对电机的永磁磁链,空载电势,电感等静态特性进行了全面的分析计算,并考虑了转子斜槽对静态特性的影响,所得结果与实测值一致,表明该文所提出了作方法可以快速、有效地分析计算双凸极永电的磁场及静态特性,适合于需要考虑不同结构参数对电机特性影响的应用场合,如优化设计等。     

盘式永磁同步电机永磁体内涡流的有限元分析

钕铁硼是采用最多的永磁体材料,虽然性能令人满意,但电导率高,耐热性差;并且由于转子散热能力差,涡流会使永磁体发热升温,从而导致部分不可逆的退磁,因此很有必要对永磁体内的涡流进行分析。针对盘式永磁同步电机自身的特点,通过二维电磁场有限元法分别求解了空载和负载时电机内的磁场和永磁体内的涡流,其中包括有铁心电机由于齿槽的存在而引起的涡流和不同电机运行速度下的涡流。为了考虑电机的运动效应和使计算结果更加精确,采用了瞬态分析,同时在划分单元时考虑了磁场的透入深度。最后根据瞬态计算出的数据绘出了磁矢位和涡流波形。波形分析得出了影响永磁体内涡流的因素以及应采取的措施。     

提高永磁电机性能新途径--磁钢工作点的确定(上)

介绍提高永磁电机性能的新途径,提出了选定磁钢工作点的新概念。对暂态工作时的电枢反应影响,不可逆磁通损失、磁钢去磁面、磁钢体积、磁钢厚度及稳定系数的关系作了分析。该研究工作对永磁交直流电机磁路结构的分析具有一定作用     

异步启动永磁同步电动机永磁体尺寸的估算

永磁体的形状与所选择的磁极结构有关,对于内置式结构,永磁体形状为矩形。异步启动永磁同步电动机的磁路结构通常选用内置串联式结构,两个磁极的永磁体串联。此时,磁路的磁动势为它们的和,而提供磁通的面积为一块永磁体的面积。等于永磁体轴向长度与永磁体宽度的乘积。永磁体的体积则取决于磁场强度H磁密B的乘积。其数值等于永磁体面积与其磁化方向长度的乘积。     

环形绕组无刷直流电机负载换向的解析模型

环形绕组无刷直流(CWBLDC)电机是一种具有梯形波反电动势的多相永磁电机,相应的换向驱动电路可实现相电流的换向。由于该电机采用梯形波反电动势,铁心材料的利用更加充分,能获得高于永磁同步电机(PMSM)的转矩密度;另一方面,采用极、槽数优化设计的分数槽绕组,能够有效抑制电机的转矩脉动,使其接近永磁同步电机的水平。良好的换向性能是该电机得以应用的前提,本文提出一种负载换向方法,其利用负载本身的电压即电机反电动势来改变相电流的方向,能够实现功率开关的零电流关断。以一台2极12槽环形绕组无刷直流电机为对象,详细分析了负载换向的过程,建立了换向过程的解析模型,讨论了换向提前角的确定方法。采用场路耦合仿真分析了该电机的换向过程,验证了解析模型的准确性,最后由原理样机试验验证了负载换向原理的可行性。     

9MW海上用半直驱永磁风力发电机电磁特性分析

随着海上用风力发电装机容量的不断增加,大功率永磁风力发电机正成为各国的研发热点。本文针对海上用大功率半直驱永磁风力发电机,进行了电磁设计,并对设计参数进行了详细的分析,包括空载特性、齿槽转矩、负载特性、损耗特性等。同时,针对大功率风力发电机相间突发短故障状态进行了研究,对突发一相短路、两相短路、三相短路下的电压、电流以及永磁体磁场强度等特性进行了分析,保证在突发相间短路下,永磁风力发电机的可靠性。基于以上分析,加工了两台9MW的永磁风力发电机,通过样机的对拖实验对理论分析进行了验证,同时证明了该样机具有良好的电磁特性,为海上用大功率永磁风力发电机的设计与发展提供了有价值的参考。     

表贴式轴向磁通永磁电机齿顶漏磁的分析计算

分数槽绕组轴向磁通永磁(AFPM)电机的齿顶漏磁较大。在利用等效磁路计算程序调试电机设计方案时,需要准确计算漏磁系数,而准确计算漏磁系数的前提是准确计算齿顶漏磁系数。根据轴向磁通永磁电机磁通路径的分布特点,针对定子齿和磁极不同的相对位置,给出了不同位置角时的齿顶漏磁解析公式。为了验证解析公式的正确性,以一台电机的设计方案为例,采用解析法和有限元法分别计算漏磁系数,结果表明解析计算结果和有限元计算结果具有较好的一致性。最后给出了齿顶漏磁与电机极数之间的关系,为电机设计和优化提供了参考。     

新型定子永磁式容错电机的工作原理和性能分析

为满足电机驱动系统在多种高可靠性领域的应用,提出一种新型的定子永磁式容错电机结构--双凸极容错(doubly salient fault tolerant,DSFT)电机。DSFT电机在结构上集中了开关磁阻电机和转子永磁式容错电机的特点,具有结构简单、可靠性高、功率密度高等优点。以一台四相8/10极DSFT电机为例,分析其结构特点、容错齿作用和运行原理。在此基础上,研究DSFT电机在正常和短路时的磁场特性,计算磁链、自感、互感等电磁特性,从理论上分析DSFT电机的容错性能。运用电路、磁路瞬态联合仿真的方法,建立DSFT电机驱动系统的场路耦合分析模型,分别对电机在正常和缺相运行状态下的转矩输出性能进行计算分析。研究结果表明,DSFT电机相与相间的独立性好,具有较强的带故障运行能力,适用于一些工作环境恶劣且要求高可靠性、高能量密度的场合。     

具有变磁阻励磁回路的永磁同步电机可变励磁功能的研究

提出了一种励磁回路变磁阻的可调励磁磁通的新型永磁同步电动机。这种电机通过永磁体的滑动调节励磁回路的磁阻，调整其提供的有效磁通，实现气隙磁场的调控功能。基于磁场力分析的简化模型，定性分析出永磁体的磁场力跟随速度增加而增大的变化规律，方向为径向指向圆心或偏离微小角度。分别就永磁体在永磁体槽中的位置、非导磁体的形状以及电机饱和等3种不同情况，运用虚位移法进行了永磁体的磁场力的定量计算。计算结果与磁场力分析结果相吻合，验证了力的变化规律满足弱磁原理中平衡离心力的 要求。     

基于等效磁路法的轴向磁场磁通切换型永磁电机静态特性分析

轴向磁场磁通切换型永磁(AFFSPM)电机是一种轴向长度短、转矩密度高的新型永磁电机。该电机磁场呈三维分布,与径向磁场电机不同,需要对该电机进行三维有限元分析,从而增加了电机分析和优化时的计算时间和成本。基于等效磁路法分析了AFFSPM电机的静态特性,建立了AFFSPM电机的非线性等效磁路模型,采用该模型计算、分析了气隙磁密、空载永磁磁链、反电动势和电感等特性,并与采用三维有限元方法的计算结果进行比较,验证了AFFSPM电机等效磁路模型的准确性,表明等效磁路模型适用于AFFSPM电机初始设计和分析。