Investigation on a choice of stator slot skew angle in brushless PM machines

The paper investigates the effects of stator slot skewing in a permanent magnet brushless DC motor. A simple analytic formula for calculation of the best angle of stack skew, which leads to nearly total reduction of the cogging torque, is developed. The skew angle obtained from this formula is different to that used by the designers of PM brushless motors. The analysis is carried out for a fractional horsepower brushless permanent magnet motor with the surface-mounted magnets using a time-stepping, multi mesh-slice finite element model, to assess the impact of this change. The steady-state characteristics and core losses are analyzed quantitatively using the elaborated numerical model. It is shown that smaller skew angles obtained from the formula lead to noticeable rise in motor overall efficiency and decrease of the core loss. The possibility of accomplishment of the desired effect of skew in a real machine is also a subject of discussion.     

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.     

一种新型无刷直流电动机谐波转矩的研究

本文对一种新型无刷直流电动机的谐波转矩进行了研究,这种电机内部除了电枢绕组以外,还还有位置传感线圈。采用能量法的观点,从宏观、总体的角度分析得出了电机的谐波转矩公式,研究了各次谐波的特性。采用斜槽积分的方法,探讨了科槽对各次谐波转矩的影响,确定了一个最佳的斜斜槽角度。     

The effect of axial variations in saturation due to skew oninduction motor equivalent-circuit parameters

In addition to reducing acoustic noise and high-frequency torque ripple, the presence of skew in an induction motor produces an axial variation in the saturation in the machine. The authors present a technique for including the effect of this variation in the calculation of the equivalent-circuit parameters. Results indicate that the axial variations in saturation due to skew can have a considerable impact on the starting performance of an induction motor     

永磁同步电机转子涡流损耗优化及温升分析

为解决永磁同步电机转子涡流损耗引起的转子温度高、永磁钢退磁等问题,建立转子涡流损耗解析表达式,分析影响参数,并以3相8极36槽V型IPMSM为例,研究定子槽口宽度、气隙长度、转子偏心距、定子斜槽角度等参数对转子涡流损耗的影响规律,完成最优参数匹配。研究结果表明,优化后的转子结构能够有效削弱电机主气隙磁密的高次谐波,从而减少涡流损耗、降低转子温度,提高电机输出性能。     

Permanent Magnet Motor Torsional Resonance Noise Reduction by Rotor Skew Phase Adjustment

Hybrid Vehicles (HEVs) and Electric Vehicles (EVs) improve drive efficiency and reduce CO₂ emissions by regenerative braking and operating the engine under optimum conditions. It is desirable to decrease the motor size and increase the maximum torque to minimize driving units. For these purposes, motors employing permanent magnets are now commonly used. The motor driving systems of HEVs and EVs must operate over variable speed ranges of up to 1:5. Over this large range, smooth, silent operation is desirable and important. The skew method is often adopted to ensure a smooth start and stop and silent operation by reducing torque ripple. However, this method possibly causes noise and motor vibration. This paper describes the mechanism of torsional resonance noise and vibrations arising from the skew method and a countermeasure to decrease them by optimizing the skew phase distribution on the rotating axis.     

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     

计及变频器和电机损耗的全变速泵站效率优化控制

针对已有研究泵站效率优化的文献均未涉及变频器和电机损耗的现状,提出计及变频器和电机损耗的全变速泵站效率优化模型,利用枚举法和约束变尺度优化算法求解模型,得到最佳控制策略.对比不计变频器和电机损耗的全变速泵站优化模型,进行大量的仿真实验和经济效益分析.结果表明,在相同给水指标下,变频器和电机损耗不影响全变速泵站效率优化控制的优化决策,在仅以求得优化决策为目的的情况下,可不予考虑,以简化建模和求解过程;但在评估泵站的节能效果时,必须考虑.     

单相感应电动机不同工作方式的性能比较

比较不同负载类型、不同起动方式以及斜槽数对单相感应电动机运行性能的影响,研究了恒功率负载下,单相感应电动机的运行性能与不同起动方式之间的关系;分析了电容起动方式时,不同负载类型对单相感应电动机运行性能的影响;对于恒功率负载、电容起动的单相感应电动机,探讨了斜槽程度对电动机运行性能的影响.     

The efficiency of the electric motor of a subsurface pump with reciprocating action and losses in a leading-in cable

The interdependence of loss in an alternating-current converter-fed motor with a frequency and level of supply voltage for an alternating-current converter-fed reciprocating action motor is shown in this work. The equations for efficiency of a supply cable with a length up to 3 km are presented. The influence of a step-down transformer and frequency converter on the losses was considered. It is determined that the line losses are commensurable with the motor losses. In this case, the line efficiency can be matched with the load and the efficiency reduced up to 50%. In addition, the transmission of practically maximum power to the motor is provided. The possibility of using the line losses for warming up a liquid is shown. In the case of a need to warm up a liquid warming, the current of the motor should have the rated value and the voltage frequency should be minimum. To decrease the losses in the line and in the motor, it is necessary to increase the voltage frequency to the rated value. Thus, it is determined whether the voltage frequency should be reduced or increased at the rated motor current. The expressions to calculate the necessary number of the modules of motor at the set well depth are presented. It is shown that, for depths 1, 2, and 3 km, it is possible to use the standard voltages of 380, 660, and 1000 V, respectively. With increasing well depth, the number of motor modules rises, which leads an increase in the voltage proportional to the well depth. An interdependence of the supply voltage of several motor modules with a well depth up to 10 km is obtained.     

大功率潜油电机的设计及模拟实验样机的制造

针对潜油电机的特殊结构,研究其定转子分段的特点对电机设计及性能的影响.通过求解三维磁场得出隔磁段所引起的漏抗,对转子冲片巧妙设计以起到斜槽的作用,在电机局部的设计计算上采用了辛普森算法和分层算法等方法,改进了潜油电机的设计方法并在此基础上设计制造了模拟实验样机,分析实验结果表明改进后的设计方法正确可行,对于提高此类电机的设计精度具有重要意义.     

高效电机设计方法的研究

在分析影响电机效率的五大损耗的基础上,针对不同损耗的特点提出了不同的解决措施,并通过针对性的试验验证了各种措施的有效性。综合比较后指出双层同心不等匝低谐波绕组在减少损耗的效果、节约成本及工艺可实现性等方面具有很大优势,用于高效电机的设计生产具有很好的推广前景。     

开关磁阻电机铁损的双频法有限元计算研究

文中对1台三相12/8结构开关磁阻电机进行了四分之一域的二维(2D)电磁场有限元分析,得到了大小和方向都随时间变化的铁心磁密矢量的X和Y分量,从而更细致地描述了电机铁心各单元磁密随时间(转子位置角度)的变化周期和规律。在无需知道电机铁心材料的损耗系数(即涡流修正因子和局部磁滞回线因子)的情况下,以磁密的计算信息和铁心材料单位体积的铁损密度数据为基础,通过双频法分离出铁损中的涡流损耗和磁滞损耗,再用频率分解法和最大磁密法分别计算这2种损耗,并对占电机铁心铁损较大比例的涡流损耗进行了离散傅里叶分解,比较各次谐波分量对铁损的影响。由间接法计算出铁损的实验值,近似地分离了铁损和杂散损耗,实验验证了该铁损计算方法的准确性。     

集中绕组单相电机的电磁计算

在对单相电机的谐波磁场进行分析后,给出了包含谐波的等效电路。分析了转子斜槽对谐波参数的影响,最终计算出集中绕组单相电机的谐波转矩和电机性能。对一台电机进行计算,结果与实测值比较吻合。     

MEASUREMENTS OF IRON LOSSES IN SINGLE-/PHASE SQUIRREL CAGE MOTORS

ABSTRACT

To determine the iron losses of a shaded pole motor, the authors have removed the shading ring, thus obtaining a single phase motor of particular characteristics. Using Veinott's method, they first obtained 60 Watts under normal conditions, that is to say, 30 Watts per kilogram of lamination. To check this value, they tried to set up two other methods, which are the object of the present paper. In both methods, the motor is represented by the equivalent circuit of a single phase-motor without iron losses, in parallel with a constant resistance which absorbs a power equal to the iron losses (which are thus assumed constant).

The first method is based on some geometrical properties of the impedance diagram of a single phase motor. The second method is analytical. A modification of Veinott's method is then presented to explain the results.     

异步电机低开关损耗的模型预测直接转矩控制

提出一种新颖的异步电机低开关损耗的模型预测直接转矩控制方法。通过建立异步电机离散时间预测模型,对不同开关矢量作用下的系统输出矢量进行轨迹外推,形成长预测范围的输出轨迹。同时分析三电平逆变器在开关切换时产生的开关损耗,以逆变器的平均开关损耗为价值函数,对不同开关矢量作用的输出轨迹进行在线评估,得到最优的开关矢量并将其作用于逆变器,从而有效降低了逆变器的开关损耗。仿真结果表明,基于该方法的驱动系统逆变器的开关损耗低,电机转矩和磁链动静态性能良好。     

驱动方式对永磁无刷直流电机损耗的影响

在分析永磁无刷直流电机方波驱动和正弦波驱动两种不同驱动方式的基础上,研究了两种驱动方式对电机损耗的影响。在正弦波控制方式下,电流超前相反电动势10°时,电机损耗最小;在方波驱动方式下,最优超前角控制时电机损耗最小。实验对比研究了最优超前角控制和id=0矢量控制两种控制策略下电机的各种损耗。     

异步电机铁心损耗计算方法的分析与研究

采用变频启动、自启动、串电阻启动等方式启动的异步电机内的组成部件中的电磁场分布并不相同,因此各组成部件的损耗分析方法也应各不相同.各种形式的斯坦梅茨方程可分析计算铁心损耗,且斯坦梅茨方程中的系数可由硅钢片制造商提供的损耗曲线获得,然而,硅钢片制造商提供的损耗曲线仅能在几个固定的频率下获得.采用了一种曲线拟合技术,可计算...     

Evaluation and Modeling of Cross Saturation Due to Leakage Flux in Vector-Controlled Induction Machines

A detailed magnetic reluctance-based computational model of an induction machine, into which a traditional rotor-flux-orientated vector control scheme has been grafted, is used to examine the influence of saturation of both main and leakage flux paths upon vector-controlled drive performance. Individual machine teeth, windings, and conductors are incorporated, as is pseudo-3-D modeling of skew. The cross-saturation effect is therefore determined from the basic dimensional and winding design data of the machine. Effective compensation methods can then be derived for practical implementation. Direct rotor flux orientation and magnitude control is used to ensure that inaccuracies in a machine-parameter-based vector control scheme are not reflected in the results for cross saturation. Results for a 15-kW four-pole induction motor with rotor skewed one stator slot pitch show that skew leakage flux is predominantly responsible for cross saturation. The skew leakage flux is shown to heavily saturate one end of the machine and to reduce the air gap flux density at the other. At 200% rated load current, this equates to an 11% reduction in direct axis flux if i_sd is kept constant. To compensate for this reduction, a 27% increase in i_sd would be required     

电磁稳态条件下的力矩电机三维暂态温度场分析

根据传热学理论建立了力矩电机电磁稳态运行条件下的三维暂态温度场的计算数学模型,给出了求解域内的基本假设及相应的边界条件,根据电磁场计算，确定了定子铁心与磁极表面的损耗热源分布。以某型力矩电机为例,应用三维有限元法计算了电机温度场的同时，也对定子铁心损耗与转子磁极表面损耗对电机温度场的影响进行了数值分析，计算结果与实测结果相吻合。