Application of the Integrated Diode Synchronous Motor to Traction Drive Motors

In this study, a traction drive electric motor was designed with a new magnet‐free motor design technique where electromagnets are generated on a rotor by utilizing changes in the spatial second harmonic of the magnetic fields. To apply the proposed technique to electric motor design, balancing the rotor and stator magnetomotive force is important. This paper presents design methods for adjusting the rotor and stator magnetomotive forces. A test motor was designed with these design methods and evaluated using a motor bench. The analytical and measurement data indicated that the proposed motor performed comparably to magnet motors.     

磁动势法五相永磁力矩电机转矩分析

五相永磁力矩电机由于极数与槽数相近,含有丰富的磁动势谐波,磁动势谐波会影响电机的转矩性能。为此,采用磁动势法分析电机的电磁转矩,通过磁能和虚位移原理推导出了电机电磁转矩的解析表达式,揭示了具有相同空间次数的定子和转子磁动势谐波相互作用才能产生电磁转矩的规律。通过对五相永磁力矩电机的定、转子磁动势谐波与电磁转矩关系的分析,指出与与主波转速一致的定子和转子磁动势谐波相互作用能提高五相永磁力矩电机的平均电磁转矩。利用Ansoft有限元软件仿真分析了电机在正弦波、梯形波和方波供电下的定子磁动势、转子磁动势以及转矩性能。结果表明,非正弦供电能够增加电机的电磁转矩,但也带来了转矩脉动,验证了磁动势法分析五相永磁力矩电机转矩的有效性和正确性。     

Loss Analysis of Permanent-Magnet Motors With Concentrated Windings—Variation of Magnet Eddy-Current Loss Due to Stator and Rotor Shapes

In this paper, we investigate losses, including magnet eddy-current loss of permanent-magnet synchronous motors with concentrated windings. A 3-D finite-element method that considers carrier harmonics of pulsewidth modulation inverters is utilized to calculate the losses in each part of the motor separately. A simple linear magnetic circuit model is also introduced in order to understand the mechanism of eddy-current loss generation in the magnet. First, the measured and calculated results are compared to verify the validity of the analysis. Next, the variation of the losses due to the stator and rotor shapes is investigated, for instance, concentrated and distributed stator windings and interior and surface-mounted permanent magnets. It is clarified that the eddy-current loss of the permanent magnet in the concentrated winding motor is much larger than that in the distributed winding motor. The difference of the loss generation mechanism due to the rotor shape is also clarified.     

Characteristics of a permanent magnet type bearingless motor

Super high-speed and high-power electric machines are required for turbomolecular pumps and spindle drives. High rotational speed and high power drives can be achieved with bearingless motors. In this paper, a bearingless motor with the principles of permanent magnet type synchronous motors is proposed. High power factor and high efficiency can be expected in permanent magnet type bearingless motors. The proposed bearingless motor is a 4 pole permanent magnet synchronous motor, in which additional 2-pole windings are wound together with 4-pole motor windings in stator slots. With currents of 2-pole windings, radial magnetic forces are produced to support a rotor shaft. Principles of radial force production of surface-mounted permanent magnet bearingless motors are analyzed mathematically. It was found that radial forces are efficiently produced by employing thin permanent magnets on the surface of rotor iron core. A test machine was built in order to measure inductance functions as well as relationships between voltages and currents     

Optimal current control methods of a non‐salient pole hybrid field‐synchronous motor for energy‐efficient and wide speed‐range operation

This paper proposes new practical optimal current control methods for a newly emerging class of non‐salient pole synchronous motors with hybrid rotor fields by both permanent magnet and winding. In practical situations with limited voltage, the extensively used permanent magnet synchronous motor hardly achieves an ideal performance that allows simultaneously both low‐speed high‐torque and wide speed‐range operations, due to its constant magnet field. Hybrid field synchronous motors (HFSM) have recently emerged to achieve ideal performance as practical motors with controllable hybrid rotor field. For HFSM, the same torque can be produced by a variety of currents due to nonlinearity between torque and currents. Consequently, appropriate determination of a set of stator and rotor current commands plays a key role in achieving possible energy‐efficient and wide speed‐range operation. Proposed methods determine the current commands corresponding to a given torque command such that total winding copper loss due to stator and rotor currents can be minimized if the exact solution exists; the best approximate torque can be produced if no exact solution exists. The determined current commands are optimal in the sense of energy efficiency or degree of approximation in wide speed‐range operation under voltage limit. New real‐time recursive algorithms searching the optimal current solution are also given. The proposed methods are analytical but practical, and their usefulness is verified through experiments. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 156(1): 70–83, 2006; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/eej.20156     

Analysis and characteristics of a permanent magnet-type bearingless motor

Super-high-speed and high-power electric machines are required for turbomolecular pumps and spindle drives. High rotational speed and high-power drives can be achieved with bearingless motors. In this paper, a bearingless motor with principles of permanent magnet-type synchronous motors is proposed. High-power factor and high efficiency can be expected in permanent magnet-type bearingless motors. The proposed bearingless motor is a 4-pole permanent magnet synchronous motor, in which additional 2-pole windings are wound together with 4-pole motor windings in stator slots. With currents of 2-pole windings, radial magnetic forces are produced to support a rotor shaft. Principles of radial force production of surface-mounted permanent magnet bearingless motors are analyzed mathematically. The relationships between radial forces and the permanent magnet thickness were derived. From these relationships, the optimal permanent magnet thickness to produce radial forces efficiently is found. A test machine was built to confirm the relationships of radial forces, currents and voltages.     

用于抑制多相异步电动机定子谐波电流的电抗滤波器

电压型逆变器驱动多相异步电动机运行时,虽然降低了转矩脉动和转子谐波损耗,却在定子绕组出现了明显的低次谐波电流.在总结现有的方法基础上,提出一种新型的电抗滤波方法.电抗器采用和多相交流电机定子类似的电磁结构,适当调整绕组的分布,使在多相电机中不产生旋转磁场的谐波电流在滤波电抗器中产生旋转磁场.这些谐波电流在多相异步电动机中仅遇到漏电抗,在滤波电抗器中却遇到高值的耦合电抗,因而有选择地对定子中的显著谐波电流进行滤波.以六相移30°的绕组结构为例,对包括滤波器的多相异步电动机建立了数学模型并进行了仿真分析,仿真结果验证了电抗器的有效性.     

基于定子磁障的分数槽集中绕组永磁同步电机应用设计与分析

分数槽集中式绕组（FSCW）存在谐波含量大的缺点,易引起定转子铁心损耗和振动噪声问题,限制了其在高端领域的应用。以采用FSCW的12槽14极永磁同步电机(PMSM)为研究对象,使用有限元软件进行仿真,分析定子非绕线齿中的磁障对磁动势谐波、电磁转矩、铁心损耗及径向电磁力的影响,并与传统永磁电机进行对比。仿真结果表明,采用定子磁障的电机能够有效降低绕组磁动势低次谐波,1、3、5次谐波分别下降了87%、84%和30%,铁心损耗减小了21.1%,低阶径向电磁力减小了20%以上,实现了对噪声和振动的有效抑制。     

Brushless DC Motors Using Unsymmetrical Field Magnetization

The prevalent types of brushless dc motors have evolved from the classical synchronous machine structures, using two-phase, three-phase, or four-phase stator windings and symmetrical N-S field magnetization patterns. The popular two-phase two-pulse brushless motor requires auxiliary means for starting and for ensuring relatively constant torque with rotor position. Three methods are used: 1) skewed stator poles, which introduce unsymmetrical air-gap reluctance and the resultant unsymmetrical air-gap magnetic field, 2) the Wessels design, which uses a rotor pole pattern of north-south-zero (N-S-0) and auxiliary stator poles, and 3) a combination of N-S-0 rotor pattern and 1200 electrical (el) pitch stator coils to produce an unsymmetrical air-gap magnetic field. The electromagnetic torque produced by motors using each of these methods is calculated using the coenergy method.     

内置式永磁同步电机不同转子拓扑结构对电机性能的影响分析

为了研究不同转子拓扑结构对8极48槽内置式永磁同步电机(IPMSM)的电磁性能和噪声性能的影响,分别建立了单层无隔磁桥、单层有隔磁桥、双层无隔磁桥以及双层有隔磁桥转子拓扑结构的内置式永磁同步电机的有限元模型。除转子拓扑结构以外,四种电机的定子拓扑结构、永磁体使用量等其它条件完全相同。首先,对电机电磁性能和噪声性能进行相关的理论分析。其次,建立四种电机的有限元模型,对四种电机的凸极率、输出转矩、转矩脉动以及空载反电势谐波畸变率等电磁性能进行比较分析,并对四种电机进行模态分析。最后,比较了四种电机的振动响应和噪声特性。结果表明,双层有隔磁桥转子结构的内置式永磁同步电机电磁性能最好,并且其噪声削弱效果也最好。     

Reducing Acoustic Noise of Axial‐Gap SRMs by Decreasing Axial Electromagnetic Force Ripple

Switched reluctance (SR) motors are motors that utilize the reluctance torque originating in the magnetic saliency between the stator and the rotor, which are made up of an electromagnetic steel sheet and windings without a permanent magnet. Because of their robustness and simple structure, SR motors are suited for use as the in‐wheel motor for traction motors of vehicles. In a flat space such as is present in in‐wheel motors, the axial‐gap structure has an advantage compared with the conventional radial‐gap structure for the space factor of a motor. An axial‐gap in‐wheel SR motor was tested in a microbus, and the bus could be successfully driven. The test results regarding the motor performance were satisfactory. However, the motor emits a loud sound. The acoustic noise of the axial‐gap SR motor is mainly caused by the axial electromagnetic force. This paper presents a method of reducing acoustic noise that is based on a model of the electromagnetic force on the axial‐gap SR motor.     

A brushless electric motor with a transverse magnetic flux and disk rotor

Brushless permanent magnet machines (BPMMs) have a greater efficiency and smaller overall dimensions than do other types of machines and are widely used in electric drives for various purposes. Two types of BPMMs are used in practice: BPMMs with a classical double-layer-distributed stator winding and BPMMs with a toothed-step stator winding. There exists another type of BPMM with a transverse magnetic flux (transverse flux motors, TFMs) which is being actively studied. In TFM electric motors, the magnetic lines of fluxes of the poles of rotor end perpendicular to the direction of rotor rotation. Stator windings in these machines are fabricated as rings coaxial with rotor, and the magnetic circuit of stator consists of separate fragments. Specialists assert electric TFMs have a higher specific power—the ratio between the output power and the mass of the machine—than the electric motors of other type. They are of interest, first and foremost, for electric drives without reducing gears. In most TFM, only a half of the poles of rotor are magnetically connected with circular phases of stator. In this work, the TFM design with disk rotor is described, in which the magnetic flux of all poles of rotor is coupled to the circular phases of stator. The stator magnetic circuit in this machine consists of P-like elements, and alternation of polarity of these elements is provided due to the change of their position. As a result, the magnetic flux coupled to the circular phase increases doubles, as do the machine torque and power. Some results of modeling of a three-phase electric motor are presented. The results were obtained using the Ansys Maxwell computer code, including a graph of the change of torque on the shaft of a machine under rotation of the rotor under conditions of sinusoidal currents in phases.     

同步发电机励磁绕组匝间短路时的电磁转矩

同步发电机的励磁绕组匝间短路故障会引起机械振动,而研究故障时的电磁转矩是分析机械振动特性的基础。文中首先基于多回路数学模型计算了短路故障后的电磁转矩,计算中全面考虑了定、转子绕组产生的各种次数、转速、转向的空间磁场之间的相互作用;对一台12kW、3对极隐极同步发电机样机进行了仿真计算及实验的比对验证;从分析故障后定、转...     

Parasitic Effects in PM Machines With Concentrated Windings

Permanent-magnet machines using concentrated windings are gaining popularity at the expense of distributed windings in various applications, mainly due to cost savings. The result is often an increased amount of parasitic effects like ripple torque, alternating magnetic fields in the rotor, unbalanced radial forces, and magnetic noise. This paper describes the reasons for the parasitic effects, in which machine topologies are particularly sensitive, and suggests measures in order to reduce their importance. Both traditional and modular concentrated windings are analyzed, as well as double-layer and single-layer windings. Measurements on a prototype motor and three commercial servomotors have demonstrated that modular motors are favorable regarding ripple torque minimization.     

基于定子谐波电流的六相永磁同步电动机双电机串联系统的仿真

电压型逆变器驱动多相电机运行时,虽然降低了转矩脉动,但却在定子绕组中出现了明显的低次谐波电流.抑制多相电机定子谐波电流的方法是串联电抗滤波器,电抗器与多相电机定子绕组电磁结构类似,使在多相电机中不产生旋转磁场的谐波电流在滤波电抗器中产生旋转磁场来抵抗谐波电流.据此提出一种新颖的两电机串联驱动系统,将电抗器换作一台多相电机,使谐波电流在这台电机中产生旋转磁场输出转矩,并且实现对两台电机转矩的独立控制.以双Y移30°六相永磁同步电动机(PMSM)为例,对两电机串联驱动系统建立数学模型并进行了仿真分析,仿真结果验证了串联驱动系统的可行性.     

Analysis of armature reaction and winding inductances of permanent magnet brushless DC motor with deep slot concentrated coils

Based on the configuration of deep slot concentrated coils, an analytical model is developed for predicting the armature reaction field produced by the 3-phase stator windings of permanent magnet brushless DC motors with concentrated coils by using the image method and the analytical functions of the armature reaction and winding inductances are proposed accounting for the influence of stator slotting. This approach is different from the method of equivalent distributed current sheet and more suitable for electric machines, which have concentrated coils and deeper slots. Under different control mode, the different analytical functions are presented. This will be helpful when further analyzing the performance of the motor. The results agree with the experiment very well. __________ Translated from Proceedings of the Chinese Society for Electrical Engineering, 2005, 25(12): 127–132 (in Chinese)     

轴径向气隙混合磁路多边耦合电机轴向励磁绕组的反电势及其位置传感器机理

无传感器控制是比较理想的电机驱动模式,是电机及电力传动领域的研究热点之一.该文在混合式步进电动机的基础上提出一种轴径向气隙混合磁路多边耦合电机,电机在提高单位体积出力的同时,在不增加传感器的条件下实现了电机的闭环控制.这种电机的结构特点决定了电机控制的灵活性,轴向励磁绕组既可以控制轴向磁通,还可以兼作转子位置传感器.该文结合轴径向气隙结构混合磁路多边耦合电机的特点,在对该种结构电机轴向绕组谐波反电势解析分析和实验研究的基础上,提出基于轴向补偿励磁线圈同时作为电机位置传感器的思想,探求了轴向励磁补偿控制绕组的传感器机理,并给出具体电路,确认了其实现的可行性.研究表明,当定子绕组三相同时通有电流的时候,轴向线圈的反电势频率是定子绕组电势的3倍,根据这个反电势信号,轴径向气隙结构混合磁路多边耦合电机可以方便的实施无传感器控制.     

集中绕组永磁无刷直流电机电枢反应及绕组电感的解析计算

基于深槽集中绕组的结构特点，采用镜像法，建立了适合集中绕组无刷电机的电枢反应求解模型。充分考虑电机齿槽影响，给出了电枢反应磁场的解析表达式，对不同控制方式下的电枢反应分别作了研究，并在此基础上推导了电机绕组电感的通用求解公式，从而为集中绕组无刷电机的参数设计和特性分析提供了理论依据。样机实验表明，其具有很好的工程适用性，理论计算与实测值吻合。     

Interbar currents and axial fluxes in healthy and faulty induction motors

Nearly 10% of all failures in cage induction motors occur on the rotor. In previous works, it has been shown that the interbar currents exist in healthy and faulty squirrel-cage induction motors. The majority of techniques detecting bar failures depend on detecting twice the slip-frequency modulation harmonic in the speed, torque, or stator current by analyzing the appropriate frequency spectrum and neglecting the interbar currents. However, the interbar currents create axial fluxes through the rotor shaft. In this paper, a three-dimensional magnetic equivalent circuit method is presented for the analysis of this phenomenon. Effects of the interbar currents on the broken rotor bar currents, and transient behavior of induction motor are also presented. Theoretical findings have been verified through experiments.     

Torque and suspension force in a bearingless switched reluctance motor

Bearingless switched reluctance motors, which can control rotor radial positions with magnetic force, have been proposed. The bearingless switched reluctance motors are characterized by integration of switched reluctance motors and magnetic bearings. These motors have two kinds of stator windings composed of motor main windings and suspension windings in the same stator in order to produce suspension force that can realize rotor shaft suspension without mechanical contacts or lubrication. For successful stable operation, accurate theoretical formulas of instantaneous torque and suspension force are necessary to a rotational speed controller and a rotor radial position controller. This paper derives the theoretical formulas of the instantaneous torque and the suspension force from an assumption of simple permeance distribution. This derivation process makes an assumption that fringing fluxes are distributed on elliptical lines. It is shown with experimental results that the derived theoretical formulas are very accurate in terms of practical application. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 157(2): 72–82, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20157