Sensorless Direct Torque Control of Five-Phase Interior Permanent-Magnet Motor Drives

This paper presents the sensorless direct torque control (DTC) technique for five-phase interior permanent-magnet (IPM) motors. By using the introduced technique, fast torque response with low ripple in the stator flux and torque of the five-phase IPM can be achieved. Having 32 space voltage vectors provides a great flexibility in selecting the inverter switching states. Therefore, the stator flux and torque can be more precisely adjusted. Position information and speed are being estimated based on the position of the stator flux linkages. The mathematical model of the five-phase IPM motor is first derived. Later, the speed sensorless DTC method of the five-phase system is introduced. A five-phase IPM motor and a five-leg insulated-gate-bipolar-transistor-based inverter were designed and fabricated in the laboratory. The control method is implemented on a TMS320C32 digital signal processor board.     

分数槽集中绕组定子磁动势的分解

介绍了单元电机的基本概念。以12槽双层的分数槽集中绕组为例,给出绕线原则,并在不确定单元电机极对数的情况下,用交流电机绕组理论、函数的傅里叶级数展开两种方法,从一个线圈、一组线圈、一相绕组到三相绕组详细推导了分数槽集中绕组各次谐波的绕组因数和磁动势,得出了分数槽集中绕组的一般特点和普遍规律。最后指出转子极对数接近但不等于定子槽数的一半是采用分数槽集中绕组的永磁电机的最佳选择。     

A novel polyphase multipole square-wave permanent magnet motordrive for electric vehicles

A novel high-power-density permanent magnet (PM) motor drive for electric vehicles (EVs) is proposed. The motor is a polyphase multipole square-wave PM motor, which can be classified as a kind of PM brushless DC motor. The distinct features of the proposed motor as compared to those of the conventional PM brushless DC motor are as follows. First, the multipole magnetic circuit arrangement enables the minimization of the magnetic yoke, resulting in the reduction of motor volume and weight. Second, the coil span is purposely designed to be equal to one slot pitch, thus saving the amount of copper used. Third, by using a fractional number of slots per pole per phase, the arrangement of the numbers of poles and slots is so unique that the magnetic force between the stator and the rotor at any rotating position is uniform, hence eliminating the cogging torque that usually occurs in PM motors. Finally, the motor can be controlled to operate at a constant torque region and a constant power region with field weakening, thus both high starting torque and high cruising speed can be achieved. Therefore, as the proposed motor drive possesses the distinct advantages of high power density, high efficiency, and superior dynamic performance, it is very suitable for EV applications. A prototype of a five-phase 22-pole 5 kW motor drive has been designed for an experimental EV     

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。     

Design considerations for fractional-slot winding configurations of synchronous machines

This paper presents some design considerations for synchronous machines characterized by a fractional number of slots per pole per phase. The main advantage of this configuration is a smooth torque, which is due to the elimination of periodicity between slots and poles. A second advantage is a higher fault-tolerant capability, making the machine able to work even in faulty conditions. However, the fractional-slot configuration presents a high content of MMF harmonics that may cause an unbalanced saturation and thus an unbearable torque ripple. A method to design fractional-slot machines is illustrated in this paper, including double-layer and single-layer windings. The analytical computation is extended to determine the harmonics of MMF distribution. Their effect is highlighted in isotropic as well as anisotropic machines. Finally, some considerations are reported to avoid unsuitable configurations.     

The steering effect PM motor drives for automotive systems

The steer-by-wire (SBW) system requires the use of enhanced fuel economy, assist action given two motor drives, the first for the mechanical steering system and the second for the torque feedback to the steering wheel. An interior permanent magnet (IPM) synchronous motor is used for the steering actuator whereas a fractional-slot surface-mounted permanent magnet (SPM) synchronous motor is used for the torque feedback.     

Low-speed high-torque drive system applying vernier motor torque

The application of the direct drive system is increasing in the field of robot and factory automation because of controllability with high accuracy. However, it requires the motor high torque at low speed. Although the vernier motor presented by Lee in 1963 could produce the reluctance torque in low speed, it involved many problems to be solved. This paper studies the reluctance torque of the vernier motor using the finite-element field analysis. Since the increase of rotor slot number is effective in producing high torque, in the model here, there are not only winding slots but also small slots on the stator teeth surfaces. Also, the rotor slots are provided in the periphery of the core more than the total number of stator slots by the pole number. The calculated torques have agreed very well with the experimental results. A prominent feature of the control scheme is to control the armature current phase based on the detected rotor slot position. Thus there is no problem such as pull-in or pull-out in Lee's vernier motor. Then the instantaneous torque is controlled by the amplitude of armature current. The experimental results on both the speed control and the position control also are shown in this paper.     

五相集中整距绕组感应电机缺相容错控制

定子绕组开路是多相电机调速系统中的常见故障。建立了五相集中整距绕组感应电机绕组开路后的方程,计算了电机绕组开路后的稳态输出电磁转矩,分析了减小转矩脉动的条件,提出了五相电机缺相容错控制方法。此方法在无需额外增加硬件的前提下,可以保证电机继续平稳地运行。对于电机定子绕组多相同时开路,建立相应的变换矩阵、重新计算电感参数后,也可以采用提出的控制方法。对电机定子绕组一相开路进行的仿真和实验结果表明,该容错控制方法可以大大减小电机缺相运行时的转矩脉动。     

MRAS-based sensorless control of a vector controlled five-phase induction motor drive

Multi-phase ac motor drives are nowadays considered for various applications, due to numerous advantages that they offer when compared to their three-phase counterparts. In principle, control methods for multi-phase machines are the same as for three-phase machines. Variable speed induction motor drives without mechanical speed sensors at the motor shaft have the attractions of low cost and high reliability. To replace the sensor, information of the rotor speed is extracted from measured stator currents and voltages at motor terminals. Vector controlled drives require estimating the magnitude and spatial orientation of the fundamental magnetic flux waves in the stator or in the rotor. Open-loop estimators and closed-loop observers are used for this purpose. They differ with respect to accuracy, robustness, and sensitivity against model parameter variations. This paper analyses operation of an open-loop and model reference adaptive system (MRAS)-based sensorless control of vector controlled five-phase induction machine with current control in the stationary reference frame. The MRAS-based sensorless operation of a three-phase induction machine is well established and the same principle is extended in this paper for an IRFOC five-phase induction machine. Performance, obtainable with hysteresis current control, is illustrated for a number of operating conditions on the basis of simulation results. Full decoupling of rotor flux control and torque control is realised. Dynamics, achievable with a five-phase vector controlled induction machine, are shown to be essentially identical to those obtainable with a three-phase induction machine. Experimental verification is also provided.     

Effect of stator chording and rotor skewing on performance ofreluctance synchronous machine

Low torque ripple in electrical machines is generally required to reduce acoustic noise and mechanical resonance vibration. To design for low torque ripple, however, affects the average torque and the power rating of the machine. In this paper, the effect of stator winding chording and rotor skewing on the average torque, power factor, and torque ripple of the normal laminated, internal flux barrier rotor reluctance synchronous machine is investigated. The two-dimensional finite-element time-step method together with the basic machine equations are used in the analysis. It is shown that to design, in general, for low torque ripple and minimal effect on torque rating of the reluctance synchronous machine, full-pitch stator windings must be used, the rotor must be skewed by a stator slot pitch, and a low number of stator slots must be avoided     

Optimization of the magnetic system of a brushless DC motor with rare-earth permanent magnets

This article discusses the causes of cogging torque pulsations in a deenergized brushless dc motor (BLDC) with a tooth stator and magnetoelectricity stimulation. Based on the causes that we identify, we propose a method of reducing cogging torque pulsations in order to improve the rotation speed uniformity of a BLDC. The method is based on optimization of the number of stator slots, which determines the type of stator winding for a given number of poles in magneto-electric machines. For the maximum possible reduction of cogging torque pulsations, it is proposed to bevel the stator slots at an angle divisible by the main tooth harmonic period. All analytical calculations were performed with the use of numerical methods for mathematical modeling of the magnetic field in the magneto-electric machines with the use of Elcut specialized software. Based on the calculation results, recommendations for the design of a BLDC with a minimum level of cogging torque pulsations were elaborated. Our theoretical studies have been checked by experimental investigations of a DBM 142-18-3 motor and applied to the design of the BLDC (DBM series) manufactured by JSC Electroprivod, Kirov. Electric motors of DBM series are used as precision electric drives for metalworking equipment, where a high uniformity of rotation speed is a major requirement.     

Design Tradeoffs Between Stator Core Loss and Torque Ripple in IPM Machines

High stator core losses can pose a significant problem in interior permanent-magnet (IPM) machines operating over wide constant-power speed ranges. At lower speeds, the torque ripple can be undesirably large in some IPM machine designs, contributing to acoustic noise and vibration. While previous work has addressed these two problems independently, this paper shows that the conditions for reducing stator core losses during flux-weakening operation, dominated by harmonic eddy-current losses in the stator teeth, can conflict with the conditions for reducing the torque ripple of IPM machines. It is also shown that the resulting design tradeoffs depend on the details of the IPM machine topologies that are under consideration. The appropriate IPM machine topologies that offer more favorable tradeoffs are identified to achieve the best possible compromise of high-speed stator core losses and torque ripple characteristics.      

A five-phase reluctance motor with high specific torque

An alternative topology for a synchronous reluctance motor (SRM) utilizing a novel five-phase, concentrated winding, wye-connected stator is proposed. The corresponding inverter requires only ten power transistors, each of which operate at a better switch utilization factor than a conventional three-phase, six-transistor bridge. It is shown that this machine is capable of producing about 10% more torque per RMS current flowing through the winding than the normal three-phase SRM     

基于SVPWM的永磁同步电动机直接转矩控制

针对永磁同步电动机（PMSM）传统直接转矩控制（DTC）系统中磁链和转矩脉动大的问题,研究基于电压空间矢量脉宽调制（SVPWM）策略的PMSM DTC.给出PMSM在αβ坐标系下的数学模型,然后结合SVPWM原理,在定子磁链Ψs幅值保持恒定的情况下,通过控制转子磁链Ψs和定子磁链Ψs间负载角δsm的增量△δsm来控制电磁转矩Te的增量△Te,从而达到控制电动机转速的目的.在Matlab/Simulink仿真环境下,对该控制系统进行了建模和仿真,与传统DTC系统比较,该方法具有更好的动、静态性能,定子两相电流的正弦度更好,磁链和转矩脉动明显减小.     

电动汽车驱动用分数槽永磁同步电机电磁噪声优化

分数槽永磁同步电机因存在较低阶次的径向电磁力,导致其电磁噪声较大。基于理论分析、Optislang多目标优化平台与Ansys多物理场有限元分析平台,对一台电动汽车驱动用8极36槽永磁同步电机的电磁噪声进行分析和优化。电机的电磁噪声主要是由作用于定子齿上的径向电磁力波使定子铁心振动变形引起,在定子齿顶开辅助槽并对其齿槽参数进行优化,以削弱径向电磁力。建立电机的二维有限元模型,利用Optislang对不同工况下的定子辅助槽及齿槽参数进行多目标优化,计算得到Pareto前沿并从中找到相对最优解。对比分析电机优化前后定子齿部的径向电磁力,将其映射到所对应的三维结构上,利用Ansys计算得到电机优化前后的电磁噪声,并通过样机的噪声试验验证了仿真结果的有效性。     

抑制分数槽永磁电机轴电压定子斜槽法

特定极槽配合的分数槽永磁电机在空载情况下会产生固有轴电压,对轴承有着不可忽视的危害,同时对电机运行的稳定性及安全性也会造成极大的影响。斜槽作为电机性能优化的常用方法,对谐波的削弱也有着很好的效果,故可以采用定子斜槽法来削弱永磁电机空载轴电压的主要谐波。首先,基于磁路原理和法拉第电磁感应定律,推导出考虑斜槽时的分数槽永磁电机空载轴电压的解析模型,分析轴电压的主要谐波成分与斜槽数的关系,给出可使轴电压得到削弱的最佳斜槽数,然后利用二维有限元法分析了不同斜槽度下的4台分数槽永磁电机的空载轴电压,结果证明了解析分析的正确性和有效性。     

双定子磁悬浮开关磁阻电机直接转矩与直接悬浮力控制

研究一种双定子磁悬浮开关磁阻电机。该电机采用内-外双定子结构,内定子和外定子上分别设置悬浮力绕组和转矩绕组。在结合拓扑结构说明其运行原理的基础上,针对该电机同时存在转矩脉动和悬浮力脉动过大的问题,提出了直接转矩(DT)与直接悬浮力控制(DSFC)策略。比较了传统方波控制策略与所提控制策略下系统的转矩脉动、悬浮力脉动以及转子径向位移波动。仿真结果表明:DT/DSFC不仅能提高系统动态响应速度,而且有效抑制了转矩和悬浮力脉动,削弱了转子径向抖振,验证了所提控制策略的有效性与优越性。     

低转矩脉动低速大转矩电主轴感应电机的设计与分析

针对低速大转矩电主轴电机转矩脉动偏高的工程实际问题,对电机不同槽配合的性能进行分析综合对比,精确选择出各方面性能较优的电机方案。针对感应电机有限元仿真瞬态场收敛速度慢、在多方案对比时求解周期长的问题,提出时谐场和瞬态场联合仿真的思路,实现电机的快速优化设计。对一台12极7.5 kW的电主轴感应电机在每极每相槽数为3、2.5、2三种不同槽配合的组合下进行二维电磁有限元分析计算,对比其在额定工况下的铁耗、绕组铜耗、转子铝耗、效率、功率因数和转矩脉动等电磁性能。结果表明了转子导条数目的增加,能够使电机电磁性能保持较高水平,特别是能够维持较低的转矩脉动水平。最后对定子槽数90和转子槽数106的槽配合方案进行了样机制作,试验验证了样机的性能,并验证了时谐场和瞬态场联合仿真的准确性。     

新型数控转台双转子永磁环形力矩电机设计

为提高电机转矩密度,研究了一种直接驱动式新型数控转台双转子永磁环形力矩电机,以适应数控机床作业空间有限的要求。定子绕组采用串联背绕的绕线方式。采用近极槽数的特殊集中分数槽绕组解决了电机多极数,低转速情况下电机极、槽配合的矛盾。通过有限元分析方法对电机性能进行分析计算,电机保持较高的绕组系数,验证了电机具有较高的转矩密度,说明了所述设计方法的合理性和有效性。     

定转子材料组合方式对再制造电机性能影响

为节约资源和提升原电机性能,将非晶材料与硅钢材料组合应用于定转子铁心进行电机再制造。根据定转子材料不同组合方式提出3种再制造方案,基于Ansoft Maxwell分析了不同组合方式对再制造电机磁密、转矩及脉动、铁耗、效率和齿槽转矩等性能的影响,确定了最佳再制造方案,并基于近似叠加算法,采用分段设置定子斜槽削弱了齿槽转矩。与原电机相比,再制造电机铁耗降低51.73%,转矩提高1.43%,转矩脉动降低6.45%,效率提升0.75%,齿槽转矩优化后降低为原电机的19%,表明了再制造电机的优越性