永磁无刷直流电机齿槽力矩分析

随着电力电子技术、永磁材料和微机控制技术的发展,永磁无刷直流电机得到了迅速发展,越来越多的应用于工业控制领域例如：电动汽车、数控机床、机器人制造等。然而,齿槽力矩的存在引起的震荡和噪声等问题使得永磁无刷电机很难应用于低速直驱控制系统中[1]。本文的目的是通过有限元法研究电机设计过程中,影响齿槽力矩的主要设计参数,从而得到优化永磁无刷电机齿槽力矩的方案。     

永磁驱动器斜极参数对齿槽转矩的影响及优化

针对开槽结构的永磁驱动器存在齿槽转矩的特点,提出一种消弱齿槽转矩的斜极优化方法。基于傅里叶分解的解析方法推导出具有斜极结构的永磁驱动器齿槽转矩解析表达式,研究了磁极斜极的主要结构参数对齿槽转矩的不同影响。以永磁驱动器齿槽转矩最小为目标,利用自适应权重粒子群优化算法对其主要结构参数进行优化,得出最优结构参数组合。最后利用ANSYS有限元仿真计算分析了优化前后永磁驱动器的齿槽转矩,仿真结果表明,优化后的斜极结构显著地消弱了永磁驱动器的齿槽转矩,避免了产生转矩波动,提高了系统的控制精度,证明本文得出的结论是正确有效的。     

不等宽永磁体削弱表面永磁电机齿槽转矩方法

与现有的改变永磁磁极极弧系数和不同极弧系数组合的齿槽转矩削弱方法不同,研究了一种新的改变极弧系数的方法削弱表面永磁电机的齿槽转矩。在该方法中,除一块磁极外,其它磁极的宽度都相同,利用解析法推导了在保证永磁体用量不变的情况下,改变极弧系数时齿槽转矩的表达式,给出了极弧系数的确定方法,并利用两台电机进行了有限元法分析。仿真结果表明:所给出的极弧系数确定方法可有效地削弱每极整数槽的表面式三相永磁同步电动机的齿槽转矩。     

Analytical approach to cogging torque calculation of PM brushless motors

This paper discusses the approach to analytical calculation of the cogging torque in permanent-magnet (PM) brushless motors. Magnetic field energy in the air gap has been used to obtain the cogging torque equations. Two equations have been derived: with the PM circumferential width taken into account, and a simplified equation, i.e., without the effect of the finite width of the PM. The effect of eccentricity has also been included. Calculation results have been compared with laboratory test results.     

Issues in reducing the cogging torque of mass-produced permanent-magnet brushless DC motor

A variety of techniques are available to reduce cogging torque in permanent-magnet brushless DC motors. Theoretically, all the techniques are quite effective for minimizing the cogging torque. This paper presents the efficacy of these methods in mass production subject to manufacturing tolerances/variations. The cogging torque minimization becomes a challenging task when the requirement is very stringent in applications such as electric power steering and robotics. Some of the known techniques for reducing the cogging torque are the magnet pole design, skewing, step skewing, and dummy slots in the stator lamination. They will be discussed in this paper considering manufacturing tolerances/variations when used in mass production. Finite-element analysis is carried out to determine the worst case scenarios. The research demonstrates that the cogging torque amplitude and frequency are highly sensitive to magnet shapes, dimensions, locations and magnetization pattern, as well as slot/pole combination. In reality, the cogging torque may not be eliminated completely but minimized to a satisfactory level depending on the application requirements.     

永磁体不对称放置削弱内置式永磁同步电动机齿槽转矩

针对内置切向式转子结构磁极偏移时,每极磁密的大小和分布都不相同的问题,基于解析法研究了偏移角度的确定方法.与表面式永磁电机不同,内置切向式结构在永磁体不对称时,每极极弧宽度会发生变化,影响每极磁密的大小和分布,两者都对齿槽转矩有影响,因此确定永磁体位置时须考虑两者的影响.基于内置式永磁同步电动机齿槽转矩解析表达式,分析每极磁密大小与分布对齿槽转矩的影响,研究磁极偏移角度的确定方法,并与表面式永磁电机磁极偏移角度进行了对比.采用有限元法计算不同偏移角度对齿槽转矩有影响的磁密谐波和齿槽转矩,有限元计算结果表明,由于考虑了磁极偏移对每极磁密的影响,磁极偏移能有效地削弱齿槽转矩.     

电枢槽口宽度对内置式永磁同步电机齿槽转矩的影响

为了兼顾准确性与计算时间,采用解析法和有限元法结合研究槽口宽度对内置式永磁电机齿槽转矩的影响.解析法确定了对齿槽转矩有影响的气隙磁导平方的傅里叶分解次数,采用有限元法计算槽口宽度变化对该傅里叶分解次数的影响.计算表明,该傅里叶分解次数与齿槽转矩的幅值随槽口宽度有相同的变化规律,能够减小该气隙磁导平方的傅里叶分解次数的槽...     

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.     

三相无刷直流电动机分数槽集中绕组槽极数组合规律研究(连载之五)降低永磁无刷直流电动机齿槽转矩的设计措施

降低齿槽转矩通常是永磁电机设计的主要目标之一.综述了永磁无刷直流电动机齿槽转矩的主要设计措施,包括采用分数槽绕组、优化磁极极弧宽和槽口宽、不等气隙、斜极和斜槽、磁极分段错位、磁极偏移、齿顶开辅助凹槽等,可供设计者参考.     

Analysis of characteristics of half-wave rectified brushless synchronous motor with permanent magnets

Previously, the authors proposed a “half-wave rectified brushless synchronous motor” as a novel servomotor. The rotor winding emf of the motor is induced by the stator current mmf which rotates at synchronous speed and pulsates at bias frequency. The field excitation is produced by the field current obtained from rectifying the emf with a diode inserted into the field winding. To improve the power factor and the efficiency, they also proposed a new-type half-wave rectified brushless synchronous motor with permanent magnets. This paper analyzes the flux distribution and the torque characteristics of the new half-wave rectified brushless synchronous motor using the finite element method. The computed torque characteristics are confirmed with the experimental results. Furthermore, the steady-state characteristic equations are derived and the effect of the modulation function waveforms on the motor performance is investigated. The theory also is confirmed by the experiments.     

无刷直流电机换相力矩波动抑制

针对无刷直流电机换相时产生力矩波动的问题,在分析了各种电流采样方式和目前广泛应用PWM控制器的转矩脉动抑制方案基础上,提出了一种新型的电流采样拓扑结构,采用单电流传感器实现了力矩电流的检测,以此建立了通过力矩电流闭环来调节直流母线电压的无刷直流电机控制系统模型,并分别给出了电机在低转速及高转速下的数学仿真分析和实验论证。仿真和实验结果表明:力矩电流采样拓扑结构实现了对产生力矩的电流的准确采集;通过在电机高速和低速运行时动态改变母线电压,保持了关断相电流和开通相电流变化速率的平衡,消除了换相所引起的力矩波动。     

Characteristic features of designing a unipolar inductor torque motor with transverse flux of permanent magnets

The development features and the design of a model of a unipolar inductor torque motor with transverse flux for the starting mode are considered. Correlations for defining the structure’s geometrical parameters are given along with an equivalent scheme of the magnetic circuit replacement, the magnetic flux equations, and expressions used to define the magnetic induction and starting moment components. A method for a torque motor design based on minimizing the power consumption is presented.     

汽车天窗电机设计参数对齿槽转矩影响及优化

提出天窗电机主要参数对齿槽转矩影响分析及其电磁优化设计模型研究.在阐述天窗电机基本结构和齿槽转矩产生机理基础上,以某汽车天窗电机为例,针对极槽配合和极弧系数设计以及转子静态偏心时的电机齿槽转矩进行计算,得到电机主要设计参数对电机齿槽转矩大小的影响规律.最后,以天窗电机齿槽转矩最小为目标,建立基于遗传算法的电机优化设计模型,获得了最优槽口宽、极弧系数和斜槽个数的设计方案,优化后的齿槽转矩明显小于原始设计方案.     

直流无刷电机中齿槽转矩的能量分析

齿槽转矩是齿槽类无刷永磁电机的固有指标,在定子绕组断电状态下,由永磁体的永磁场与定子铁芯的齿槽结构相互作用形成电磁力,进而在圆周方向产生周期性的固定转矩。本文从能量守恒的角度出发,根据齿槽转矩的产生机理推导出齿槽转矩与电磁结构的公式关系,以3对极和6对极两款直流无刷电机为例,利用二维有限元法分析了齿槽转矩在圆周方向的能量分布,研究表明,相同槽数的电机在一个周期内符合能量守恒定律,极对数的不同会造成齿槽转矩不同,通过选择合理的方法能够有效的利用齿槽转矩达到电机断电制动的效果。