对逆变器供电异步电动机测试标准化的贡献

众所周知,由于逆变器的输出电压为非正弦波形,故逆变器供电异步电动机的铁耗、铜耗比电网供电的异步电机要大。为了寻求确定这类电机损耗的简易方法,本文在论述了这类电机的铁耗、铜耗的理论基础上,给出了证实该理论的试验结果。逆变器供电异步电动机的铜耗与铁耗     

异步电动机损耗的测定

介绍了异步电动机铁耗和机械耗比较准确的测试方法，从而为异步电动机特性的测试与研究提供了可靠的依据。     

异步电动机损耗的测定

介绍了异步电动机铁耗和机械耗比较准确的测试方法，从而为异步电动机特性的测试与研究提供了可靠的依据。     

高压高效三相异步电动机空载附加损耗分析与计算

对高压高效三相异步电动机空载附加损耗产生的原因以及计算方法进行分析。并以一台1000k W电动机为例,建立求解高压高效三相异步电动机的二维瞬态场有限元模型,准确计算了电动机空载运行时的气隙磁密。在二维瞬态场计算结果的基础上,计算电机空载运行状况下的附加损耗。最后通过铁耗分离试验得到电机空载附加损耗的试验值,并与计算值进行对比分析,验证了该计算方法的准确性。     

浅谈高效三相异步电动机设计

简要介绍高效三相异步电动机设计的一般思路,以及限制定子铜耗、转子铜耗、铁耗、机械损耗的一般方法,力求以Y2系列三相异步电动机为基础,开发设计符合国际、国家标准的高效三相异步电动机,并对开发设计过程的实验经验进行总结。     

永磁同步电动机空载铁耗研究

从产生根源出发,对永磁同步电动机空载铁耗进行细致分类。在此基础上,利用有限元法和Bertotti铁耗计算模型,以一台5 k W、3 000 r/min永磁同步电机为例,对正弦波供电永磁同步电动机的空载铁耗分布特性进行分析计算,得到基本铁耗与空载杂散损耗的比例关系以及不同因素所引起的空载杂散损耗分布规律。进而,研究了变频器供电空载电流时间谐波引起的谐波损耗,分析了不同极槽配合对变频器供电永磁同步电机的谐波损耗影响规律。最后,通过多台样机的空载铁耗试验,验证了计算的正确性。     

高压三相异步电动机定子铁心铁损试验

理论联系实践，系统地描述了大中型高压三相异步电动机定子铁心铁耗试验的方法、过程及要求。     

实心转子力矩电动机转矩特性的计算

忽略电机铁耗后,实心转子异步电动机的等值电路如图1所示。图中 r_1及 x_1分别为定子电阻和电抗,r_2及 x_2分别为转子电阻和电抗,x_m 为电机激磁电抗,r_1及 x_1的计算方法与三相异步电动机相同。x_m 可按下式计算:     

气隙磁密与负载对异步电动机杂散损耗的影响

文章分析了异步电动机气隙磁密对空载杂耗的影响以及气隙磁密和负载对负载杂耗与电动机总杂耗的影响。并提出了一种从铁耗中分离空载杂耗的方法。     

高速电动机损耗分析及温度场计算

高速电动机的损耗密度大,散热困难,因绕组绝缘易过热而出现寿命减短甚至失效的问题,因此准确地计算异步电动机各个损耗以及准确预测电动机温度场变得尤为重要。本文以一台额定转速为40000r/min的高速异步电动机为例,进行了高速异步电动机损耗的全面分析,基于磁-热单向耦合的有限元方法对高速异步电动机的整体温度场进行了准确计算,并与实验结果进行比较。研究表明,可以忽略高速异步电动机的转子铁耗,高速异步电动机在运行超过某一转速后,电动机温升呈指数规律增加,需要对电动机温升进行监测,同时,磁-热耦合的方法具有一定的准确性。     

Torque ripple minimization with optimized <Emphasis Type="Italic">i</Emphasis><Subscript><Emphasis Type="Italic">sx</Emphasis></Subscript> estimation in vector control of current source inverter induction motor

In variable speed applications of high-power induction motors, current source inverters are usually used instead of voltage source inverters. Power switches delay and switching losses in high-power ranges, prevents inverters to operate properly in high frequencies. So the voltage and current waveforms of the motor supply consist of high harmonic content causing a high-torque ripple. One of the parameters that influences the torque ripple most is the stator flux reference value. Motors do not usually operate in their nominal load. Therefore, the optimum value of the flux is not equal to the nominal value. In this paper, an optimal i _sx reference for vector control system of current source inverter fed induction motor is produced by applying a simple estimator. Simulation results show that torque ripple has been reduced, especially in the loads less than their nominal power, as significantly as power factor has been improved. Also flux reduction causes to noticeable reduction in core and switching losses.     

一种具有中点平衡功能的三电平异步电机直接转矩控制方法

对三电平逆变器供电异步电机直接转矩控制(DTC)系统进行了研究。以固定合成矢量为基础，提出了一种三电平异步电机DTC控制方法，并使用基于三相输出电流方向及中点不平衡方向检测的中点平衡Bang-Bang控制方法来控制中点电位平衡。使用文中的DTC方法，可以抑制三电平直流侧中点不平衡，限制输出电压dv/dt，减小开关损耗，同时获得良好的电机调速特性。实验结果证明了该控制方法的可行性。     

ABOUT THE DESIGN OF VERY HIGH FREQUENCY INDUCTION MOTORS FOR SPINDLE APPLICATIONS

Abstract

In the paper the authors deal with induction motors used in electrical spindles and fed by high frequency inverters. The design problems of high frequency machines are analyzed by the electromagnetic, the mechanical and the thermal points of view. The possibility to use the classical relations adopted to calculate the equivalent circuit parameters for standard motors at 50?Hz is carried out and the results are compared with the experimental ones. A brief overview of problems related to the mechanical design (bearings, lubrication, shaft stiffness) and to the thermal design is reported. Finally, starting from both the simulation and the experimental results, some specific criteria for the electromagnetic design are well focused.     

Comparative Study of the Losses in Voltage and Current Source Inverter Fed Induction Motors

The losses in an induction motor fed from six-step voltage and current source inverters are calculated and a comparison of efficiencies when supplied from these sources is given. The equivalent circuit that includes the effect of space harmonics and corrected for the skin effect in rotor bars is used for the calculation of main and stray copper losses. Stray iron losses due to magnetomotive force (MMF) and permeance harmonics, end leakage and skew leakage are also considered. Losses in the motor when supplied from these sources are also calculated using the modified equivalent circuit having stray and core loss resistors and their efficiencies are compared.     

基于固定合成矢量的高性能三电平异步电机直接转矩控制系统研究

针对具有中点电位平衡功能的电平异步电机直接转矩控制（DTC）方法会引起较大的定子磁链和转矩脉动的缺点,改进固定合成矢量的合成方式,提出了适用于高性能三电平异步DTC系统的“24矢量”法和“24矢量＋变调制比”法。从磁链、转矩控制性能的角度出发,分析了它对电机性能改善的贡献。这两种方法物理概念清晰、结构简单、易于实现,且保留了原同定合成矢量方法的优点。实验结果证明了控制方法的可行性。     

Loss calculation of induction motors considering harmonic electromagnetic field in stator and rotor

A method of loss calculation for induction motors is proposed. The combined 3D–2D time‐stepping finite element analysis is carried out to obtain the copper loss and the time variation of the magnetic field in the motor. The iron loss is calculated approximately considering the time variation of the magnetic field direction and the minor hysteresis loops caused by the time‐harmonic fields using practical computer resources. The proposed method is applied to four types of induction motors, which are the solid rotor induction motors with/without slot and the cage induction motors with/without skew. The measured and the calculated total losses and the iron losses agree well in all cases. The differences of the loss distributions of each motor are also compared and investigated. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 147(2): 63–73, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10305     

Computation of no-load iron losses including spatial harmonics and tooth pulsation components for cage motor

The contribution of spatial harmonics and tooth pulsation in iron losses of three phase squirrel cage induction motor has been calculated using lumped circuit approach. An equivalent circuit of the three phase induction motor considering stator magnetomotive harmonics has been used for the calculation of the same. An empirical formula has been developed and validated for determination of tooth pulsation losses. The usage of lumped parameters circuit considering magnetomotive force harmonics for predicting the iron losses components has not appeared in the literature. Here iron losses due to fundamental, spatial harmonics components and tooth pulsation for various motors with different designs and polarities have been deter-mined and compared with experimental results. It is found that the iron losses due to the stator magnetomotive harmonics is in same range as that due to fundamental component, the tooth pulsation losses are in the range of 25 to 35% for 2 pole, and 20 to 30% of total iron losses for 4 pole induction motors. The percentage errors between computed and average experimental results for total iron losses are within acceptable limits (±5%) without taking too much of computation time compared to the numerical methods.     

Modeling of iron losses of permanent-magnet synchronous motors

Permanent-magnet (PM) motors offer potential energy savings as compared with induction motors because of the virtual elimination of rotor loss and the reduction of stator loss from operation near unity power factor. In PM machines, iron losses form a significant fraction of the total loss partly due to the nonsinusoidal flux density distribution. Design optimization therefore requires good means of predicting these iron losses. Finite-element analysis can be employed but this approach is cumbersome and costly when used in the many iterations needed in optimizing the design. This paper presents a set of improved approximate models for the prediction of iron loss. They can be used in design optimization programs and, since they are directly related to machine dimensions and material properties, they also provide quick insight into the effects of design changes. A time-stepped finite-element method is employed to evaluate the iron losses in a range of typical PM machines and the results are used to evaluate the adequacy of the models. The predictions of overall iron losses are then compared with measurements made on two PM motors.     

Application of the method of individual losses for determining the efficiency of an induction motor fed from a polyharmonic voltage source

Application of the method of individual losses for the determination of the efficiency of induction motors fed from frequency converters is theoretically justified and the accuracy of the method is assessed. Theoretical conclusions are confirmed by experimental results.