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.     

Magnetic field analysis of a squirrel cage induction motor considering rotor skew and higher harmonics in the secondary current

This paper describes a method to analyze harmonic magnetic fields of squirrel cage induction motors considering rotor skew and higher harmonics in the secondary current. The proposed method is based on a two‐dimensional finite element method. The rotor skew structure is expressed by multiple 2D finite element mesh models, produced in suitable axial positions, and the magnetic field in each mesh model is calculated by the revised secondary current taking into account the skew effect. The secondary currents, magnetic flux densities, and electromotive forces are calculated by the proposed method. Then the differences between a skewed rotor and a nonskewed rotor are discussed. From the comparison between the calculated and the experimental results, the proposed method is shown to be appropriate and useful for quantitative estimation of harmonic components of induction motors. © 1999 Scripta Technica, Electr Eng Jpn, 129(2): 98–109, 1999     

Induction motor drives with minimal power losses

The goal is to synthesize a control system for an induction motor such as to ensure operation with minimal power losses. Standard nonlinearity and losses in the steel of the motor’s stator are taken into account in MatLab simulation. The proposed control system reduces the losses by up to 25% in comparison with classical scalar control.     

笼型异步电动机转子故障的判断

电机转子出现故障后,定子电流的频谱图上将出现一个特有的电流脉动成分(转子断条)或独特的频谱成分(气隙偏心),根据其大小和变化情况,判断转子出现了何种故障。     

Additional no-load losses in inverter-fed high-speed cage induction motors

An analysis of additional high-frequency losses in high-speed cage induction motors with closed rotor slots under sinusoidal and inverter supply at no load is presented. Calculated losses are compared with experimental results obtained by measurement on a 270 kW, 16,200/min, prototype motor, at both the delta and star connections of the stator winding. The main additional losses of the prototype motor investigated due to inverter supply are eddy current losses in the stator winding. Both measurement and calculation show that, at the delta connection, the additional losses are higher due to the lower modulation degree of the inverter, causing higher harmonic voltage amplitudes.List of symbols B magnetic flux density, T - b _sheet width of iron sheet, m - b _bar mean width of rotor bar, m - b _sd mean stator tooth width, m - b _Qm mean slot width, m - b _LT square wire side, m - f frequency, Hz - h _bar rotor bar height, m - h _br rotor slot bridge height, m - h _sy stator yoke height, m - I current (rms value), A - k ordinal number of voltage harmonic - k _C Carters factor - k _dHy hysteresis deterioration factor for teeth - k _dFt eddy-current deterioration factor for teeth - k _Fe iron stack fill factor - K _l1k first-order skin effect coefficient of stator inductance for kth voltage harmonic - K _l2k second-order skin effect coefficient of stator inductance for kth voltage harmonic - K _1k first-order skin effect coefficient of stator resistance for kth voltage harmonic - _2k second-order skin effect coefficient of stator resistance for kth voltage harmonic - k _yHy hysteresis deterioration factor for yoke - k _yFt eddy-current deterioration factor for yoke - k _w1 winding factor for fundamental space harmonic - l _b length of winding overhang, m - l _Fe core length, m - L _dc inductance at d.c. current, H - L _r rotor inductance, H - L _s stator inductance, H - M torque, Nm - m _T number of vertically arranged coils in slot - m _TZ number of vertically arranged conductors in slot - n _N rated speed, 1/min - p number of pole pairs - p _Ft eddy current losses per iron mass at 50 Hz, 1 T, W/kg - p _Hy hysteresis losses per iron mass at 50 Hz, 1 T, W/kg - P _Cu copper losses, W - P _Fe iron losses, W - P _Fe,Hy hysteresis losses, W - P _Fe,Ft eddy-current iron losses, W - P _fr friction and windage losses, W - Q _r number of rotor slots - Q _s number of stator slots - R _s stator phase resistance, - R _r rotor phase resistance, - R _dc resistance at d.c. current, - s slip - s _k slip for kth harmonic - U voltage (rms value), V - V volume, m³ - N number of turns per phase - z ₁ average number of conductors in one turn, lying side by side - z ₂ average number of vertically arranged conductors per turn - air-gap length, m - magnetic flux, Wb - electric conductivity, S/m - permeability ( ₀=4×10^–7 H/m: permeability of vacuum), H/m - _r relative permeability - _Fe mass density, kg/m³ - _s leakage coefficient for stator winding - _p pole pitch, m - _sd stator tooth pitch, m G. Joksimovi is on research leave from University of Montenegro, Montenegro, Yugoslavia     

鼠笼异步电机起动性能的时步有限元计算

时步有限元方法是计算鼠笼异步电机暂态起动特性的一种有效方法,本文针对当前该方法在工程应用中存在的问题展开了研究。在转子转动的处理方面,通过对现有方法进行改进,得到了一种新的处理有限元运动问题的方法——边界耦合法,解决了现有方法存在的效率低、通用性不强和时闻步长不确定等问题。本文还讨论了转子电路方程的建立和电磁转矩计算等方面的问题。     

Finite-element models for cage induction motor analysis

Two methods for predicting the performance of cage induction motors using finite elements are described. The first, which is suitable for steady-state analysis, uses a phase-band model for the stator together with a single slot model for the rotor. These are used in an iterative procedure to determine the components of the familiar per-phase equivalent circuit. The second method, which is suitable for transient analysis, uses a time-stepped coupled circuit model for the machine, together with magnetostatic finite-element field solutions that are used to update the circuit parameters. Both methods are illustrated by comparison between experimental and computer characteristics for a four-pole 4.5 kW motor     

笼型转子断条感应电动机的易解数学模型

针对断条破坏了电机原有对称关系而使建模仿真变得困难,采用综合矢量法,建立了转子断条感应电动机易于求解的数学模型.对电机暂态及稳态仿真揭示了定子电流幅值与转矩随时间脉动的故障特征,得出了转子导条电流分布规律,表明与断条相邻及相距一对极距的导条电流最大.引人关注的是在转子端环间出现端电压,其值反映了转子电路不对称程度;揭示了故障特征随电机负载变化规律.定子电流实测与仿真结果相吻合证实了结论正确,有助于感应电机在线故障诊断.     

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     

Variable speed drive with current source inverter supply and permanent magnet synchronous motor compared with cage induction motor

Contents Industrial drives with adjustable speed and a progressive torque speed characteristic may be built with a considerably higher efficiency by using the permanent magnet excited synchronous motor instead of the squirrel cage induction motor. To prove the benefit, the power losses of two experimental drive systems were determined by calculation and measurement as well. The air gap damper losses of the synchronous machine induced by the commutations of the stator current and the slot and winding harmonics of the air gap field are calculated by solving the 2-dimensional diffusion equation using harmonic series and by applying the Poynting-vector method. It turns out that the power losses of the drive are reduced by 44%.

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Drehzahlstellbarer Antrieb mit stromeinprägendem Frequenzumrichter und permanentmagnetisch erregtem Synchronmotor im Vergleich mit dem Käfigläufermotor

Übersicht Industrieantriebe mit stellbarer Drehzahl und progressiver Drehmoment-Drehzahl-Kennlinie können mit wesentlich besserem Wirkungsgrad gebaut werden, wenn anstatt eines Asynchron-Käfigläufermotors ein permanent erregter Synchronmotor verwendet wird. Um den Nutzen nachzuweisen, werden die Leistungsverluste von zwei experimentellen Antriebssystemen durch Berechnung und Messung bestimmt. Die Verluste des Luftspaltdämpfers der Synchronmaschine, die durch die Kommutierung des Ständerstromes und die Nut- und Wicklungsoberwellen des Luftspaltfeldes entstehen, werden durch Lösung der zweidimensionalen Diffusionsgleichung mit harmonischen Reihen und mit dem Poynting-Vektor berechnet. Es stellt sich heraus, daß die Leistungsverluste des Antriebs um 44% reduziert werden.

     

Fuzzy control of integrated current-controlledconverter-inverter-fed cage induction motor drive

This paper presents a performance analysis of a vector-controlled cage induction motor drive. The drive is fed from a current-controlled converter-inverter system. The pulsewidth modulation current control technique is used to derive the switching signals for the converter, as well as the inverter. Closed-loop control of the cage induction motor utilizes a fuzzy proportional integral derivative speed controller. The advantages offered by the current control converter-inverter link are exploited. In order to examine the dynamic performance of the drive system, its model is simulated and results are analyzed. The potential applications of this particular drive system are outlined     

Characteristic analysis of an induction motor with an unequal slot pitch cage rotor

Recent developments in induction motors have been moving forward reducing the size and weight of motors. At the same time, there are demands for much quieter operating conditions. Various design methods have been applied to reduce the vibration and acoustic noise of induction motors. One method is to make the slot pitches of the cage rotor unequal, to avoid the resonance with the natural frequencies of the stator frame. In this paper, our purpose is to create guidelines for reducing noise. As the first step for this purpose, we developed a method to analyze the voltage and torque equations of an induction motor with an unequal slot pitch cage rotor and discussed the characteristics from the analyzed currents. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 140(2): 44–52, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10032     

多断条笼型转子感应电动机导条电流分布

为研究转子断条感应电动机的导条电流分布问题,采用基于拓展的综合矢量法建立了易于求解的数学模型.其数学模型的暂态及稳态仿真运行揭示了导条电流分布特征及最大导条电流与断条数量、相对位置的关系.结果表明,导条电流随空间变化的周期为一对极;具有最大电流的导条位置与断条相邻或相距一对极距;在多断条情况下,最大导条电流数值随断条位置而改变;当断条相对位置为一对极距时,最大导条电流达到相应断条数目的最高值;在特殊断条位置情况下,所有正常导条电流数值相等.所得研究结果有助于对感应电机在线故障诊断作正确评估.     

Magnetic suspension force in an induction bearingless motor with a squirrel cage rotor

Theoretical equations of magnetic force in an induction bearingless motor have been reported. In the bearing‐less motor, both 4‐pole and 2‐pole windings are stored in stator slots for torque and suspension force generation. In the analysis, squirrel cage rotor currents are considered. These currents are induced by both torque and suspension winding currents. Inductance matrix is represented by four sets of three‐phase windings, thus a 12×12 matrix is constructed. A simplification and reasonable assumptions are introduced to obtain understandable expressions for suspension force and torque representation. The rotor flux linkages in an induction bearingless motor are derived, and a simulation model of suspension force is then constructed. It is shown that the response and the phase of suspension force are delayed in the case of cage rotors. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(3): 77–87, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20340     

Stray losses due to inter-bar currents of skewed cage induction motors at no-load

Contents In accordance with present-day efforts to reduce power losses in electrical machines, an analytical approach to estimate the influence of contact resistances between the skewed rotor cage and its laminated iron core on the amount of stray losses of induction motors is made in this paper. Equations for calculation of resistances of the rotor iron core, with which the stray losses due to inter-bar currents are taken into account, are presented.

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übersicht In übereinstimmung mit neuzeitlichen Bemühungen, die Verluste von elektrischen Maschinen zu vermindern, ist in der vorliegenden Arbeit eine analytische L?sung zur Bewertung des Einflusses der Kontaktwiderst?nde zwischen dem geschr?gten K?fig und Blechpaket des Rotors auf die Zusatz und indirekt auf die Gesamtverluste von Asynchronmaschinen angegeben. Es werden die Gleichungen zur Berechnung des Blechpaket-Widerstandes des Rotors angegeben, mit denen man den Anteil der Zusatzverluste berechnet die, der von Querstr?men im Rotor verursacht wird.

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Received: 21 March 2000     

导磁导电复合笼条转子感应电动机性能计算

为了研究既导磁又导电的复合材料作为高功率电机的转子材料时对其性能的影响,对37k W感应电动机进行了复合材料和普通铸铝材料的对比分析。采用二维电磁场有限元计算方法,建立了37k W感应电动机的数学模型和物理模型进行分析。在考虑工艺可行性的情况下,优化设计了三种适合复合笼条嵌入的转子槽型,分析复合材料放置位置对电机起动性能和运行性能的影响。同时,改变转子槽内合金材料的宽度,分析复合材料放置面积对电机起动和运行性能的影响,并与采用相同机座号的普通铸铝材料的感应电动机进行性能比较,证明了复合笼条转子应用于37k W感应电动机具有优越的起动性能和良好的运行性能,为新型感应电机设计和电工材料的选取提供一定的可行参考。     

不同转子结构对复合笼条转子感应电动机性能的影响

针对复合笼条转子感应电动机运行性能稍差的弱点,提出3种不同转子结构的复合笼条转子感应电动机,并对不同转子结构的磁场进行分析,计算3种转子结构复合笼条转子感应电动机的起动性能和转子槽漏感,对转子导条电流与转子导条损耗进行分析,此外还分析3种转子结构复合笼条转子感应电动机的运行性能。通过起动与运行性能计算结果与实测结果的对比分析,说明了计算结果满足工程实际的需要,分析结果表明转子采用复合导条与铸铝导条交替式的复合笼条转子感应电动机比转子全部为复合导条的复合笼条转子感应电动机的效率和功率因数有较大幅度提高,为电机优化设计提供参考依据。     

Calculation of stray losses in a single-sided linear induction motor

Contents The paper describes a method of the stray losses calculation in single-sided linear induction motors (LIMs). The stray losses produced by the higher space harmonics of the primary winding and by the primary slots are discussed. Examples of calculations for a small and a large-scale LIM have been included.

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Berechnung von Zusatzverlusten bei einem einseitigen linearen Induktionsmotor

Übersicht Der Artikel beschreibt eine Methode zur Berechnung von Zusatzverlusten bei einseitigen, linearen Induktionsmotoren. Die Zusatzverluste, die durch höhere räumliche Oberwellen der Primärwicklung und die primärseitige Nutung entstehen, werden besprochen. Berechnungsbeispiele für einen kleinen sowie einen großen Linearmotor sind beigefügt.