Analysis of inverter-fed high-speed induction motor consideringcrosspath resistance between adjacent rotor bars

The purpose of this work is to analyze the steady state performance of an inverter-fed high-speed induction motor with trapezoidal rotor bars taking into account crosspath resistance between adjacent rotor bars. The performance of the induction motor drives for various crosspath resistances of two kinds of rotor slot shapes, a rectangular bar and a trapezoidal bar, is discussed on the basis of theoretical and experimental results of a 2.2 kW 500 Hz 15000 rev/min three-phase induction motor. It is also shown that the equivalent rotor resistance and leakage reactance change with crosspath resistance between adjacent rotor bars for various values of the fundamental supply frequency, the rotor slip, and the harmonics. The results of this research will be applied for design consideration of a high-speed induction motor with uninsulated rotor bars     

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.     

Sensorless control of inverter-fed induction motor drives

Sensorless control is considered to be a lower cost alternative than the position or speed encoder-based control of induction motors. Two popular sensorless control methods, namely, the model reference adaptive system (MRAS) and the Luenberger observer (LO) methods are compared for speed and torque control characteristics. They are also compared against the well-known vector control principle. For the drive system simulated, the torque and speed obtained from sensorless control are almost identical to those obtained from the vector control method. However, the torque ripple for the sensorless methods is observed to be higher than vector control-based method. The MRAS method introduces higher torque ripple when compared to the Luenberger observer. In addition, speed estimation methods employed in sensorless control are more sensitive to motor parameter variations.     

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.     

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     

Quasi-resonant inverter-fed direct torque controlled induction motor drive

A quasi-resonant inverter-fed induction motor operated under direct torque control (DTC) scheme is modeled and analyzed with SABER simulator. The dc link voltage is clamped to source voltage. All the devices in the resonant link and inverter except auxiliary switch in the resonant link are operated soft under zero-voltage switching (ZVS). The auxiliary switch is turned on under zero-current switching (ZCS), but turned off hard. This scheme has been implemented on a laboratory-sized experimental setup. A comparison of simulation and experimental results under identical operating conditions were presented.     

Fault detection of broken rotor bars in induction motor using a global fault index

Induction motors play a very important part in the safe and efficient running of any industrial plant. Early detection of abnormalities in the motor would help to avoid costly breakdowns. Accordingly, this work presents a technique for the diagnosis of broken rotor bars in induction motor. Stator voltage and current in an induction motor were measured and employed for computation of the input power of one stator phase. Waveforms of the instantaneous power and line current were subsequently analyzed using the Bartlett periodogram. Different global fault indexes on the instantaneous power spectrum and on the line current spectrum for the fault detection are evaluated. Several rotor cage faults of increasing severity were studied with various load effects. Experimental results prove the efficiency of the employed method.     

On the steady-state analysis of the inverter-fed induction motor

Contents The analysis of the induction motor based on the signal flow graphs is carried out. It is shown that the state transition matrix can be determined in a systematic and straightforward way using Mason's gain formula. This method is found computationally very much superior to other methods available in the literature. There is a considerable reduction in the CPU time. The presence of an input signal also does not pose any problems, as inherently the transition signal flow graph includes its effect also.

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Das stationäre Verhalten der stromrichter-gespeisten Asynchronmaschine

Übersicht Es wird in der vorliegenden Arbeit das stationäre Verhalten der stromrichter-gespeisten Asynchronmaschine auf Grund des Signalflußdiagramms untersucht. Die Anwendung der Masonschen Regel liefert unmittelbar die, State Transition Matrix' mit einem CPU-Zeitaufwand, der geringer ist, als der der in der Literatur bekannten Methoden. Beliebige Eingangssignale lassen sich in einfacher Weise behandeln, da diese im Signalflußdiagramm repräsentiert werden können.

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List of Symbols i _ds,i _qs direct and quadrature axis currents of stator - i _dr,i _qr direct and quadrature axis currents of rotor - i _dr(0),i _qs(0) initial values of d-q currents of stator - i _dr(0),i _qr(0) initial values of d-q currents of rotor - I _ds(s),I _qs(s) Laplace transforms of d-q currents of stator - I _dr(s),I _qr(s) Laplace transforms of d-q currents of rotor - L _s,L _r Self inductances of stator and rotor - M Mutual inductance between stator and rotor - R _s,R _r Resistance per phase of stator and rotor windings - R ₁,R ₂,R ₃,R ₄ Roots of characteristic equation - V _ds V _qs Direct and quadrature components of stator voltage - _ds, _qs Direct and quadrature components of stator flux linkages - _dr, _qr Direct and quadrature components of rotor flux linkages - _s Synchronous angular velocity - _r Rotor angular velocity - T _d Torque developed     

Decoupled direct control for PWM inverter-fed induction motor drives

A new direct torque and stator flux control method is presented for pulsewidth modulation (PWM) inverter-fed induction motors. This new strategy, called decoupled direct control (DDC), is based on a decoupling matrix that allows for the separate control of the stator flux and the torque. This method is compared to the well-known direct field-oriented control (FOC) and stator flux vector control (SFVC) methods. Two DDC-based methods are presented. The first determines the stator voltage vector such that the torque and the flux track their respective reference trajectories in one sampling time. The second sets separately the dynamic behavior of the torque and stator flux errors by the use of proportional-plus integral (PI)-type controllers. These methods take into account the full motor dynamics without the need of a coordinate transformation and reduce significantly computation requirements compared to FOC and SFVC. The two proposed strategies have been implemented experimentally and comparisons with FOC and SFVC were carried out. The obtained results show the effectiveness of the proposed PI-DDC strategy.     

变频电源笼型异步电机断条故障诊断仿真

为了探讨笼型异步电动机转子导条断裂故障诊断的有效方法,根据多回路电机模型参数及正弦脉宽调制(SPWM)原理,建立了变频电源供电笼型异步电机在正常情况和转子断条故障情况下的运行状态仿真模型,并在MATLAB仿真环境比较电机定子单相电流频谱及三相平均瞬时功率频谱。通过分析检验了仿真系统模型的可行性和实用性,证实了平均瞬时功率频谱比电机定子电流频谱具有更佳的断条故障特征分辨力和故障判断准确性,尤其是在变频供电情况下优势极为突出,从而确立了合适的断条故障判据。     

Lightly ferromagnetic rotor bars for three-phase squirrel-cage induction machines

The concept of lightly ferromagnetic rotor bars to improve the starting performance of squirrel-cage induction motors is presented in this paper. Although the induction machines are popular for their ruggedness and simplicity, their starting torque is low and the starting current is 5-8 times higher than the rated current. A simple solution to this problem is the introduction of new rotor-bar material with lightly ferromagnetic properties, which in turn improves the starting power factor due to enhanced skin effect. Relevant electromagnetic theory supporting this is e presented in this paper. A computer simulation also produced expected results. A 1-hp induction machine has been tested to verify the proposed methodology.     

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。     

Improved current source GTO inverter-fed induction motor driveswith PWM-controlled thyristor converter

An improved current-source GTO (gate turn-off) inverter system for driving an induction motor at high frequency was developed. This system is composed of an inverter using GTOs and a PWM (pulsewidth-modulated)-controlled thyristor rectifier. The energy rebound circuit in the inverter is used to turn off the thyristors in the rectifier and to apply PWM control techniques. This circuit plays an important role in the treatment of reactive power in a load. The capacitors connected to the AC input terminal to improve PWM control also function as a filter. Thus, the waveforms of the input voltage and current become almost sinusoidal. Principles and circuit operations of the rectifier section are described in detail. The current-source GTO inverter is used to drive a 5.5 kW induction motor. The experimental waveform and characteristics for the tested motor drives are given. It is shown that the harmonic components of the input voltage and current are eliminated or reduced by using the PWM control technique without spoiling the inherent characteristics of the current-source GTO inverter     

基于MIRPSA的感应电动机转子断条数目诊断判据

在感应电动机转子断条数目诊断方面,电机定子电流信号分析(MCSA)类方法已经建立明确的解析判据,而电机瞬时无功功率信号分析(MIRPSA)类方法缺乏理论支撑。为此,针对转子断条故障推导了感应电动机瞬时无功功率特征分量的幅值与转子断条数目间的数值对应关系,由此建立了具有解析意义的基于MIRPSA的转子断条数目诊断判据。感应电动机转子断条故障仿真与实验证明了所提判据的有效性。     

基于Hilbert变换的感应电机转子断条故障研究

在分析当前主要诊断方法的基础上,采用Hilbrt变换频谱分析方法对不同负载情况下的感应电机转子断条故障进行研究。通过与FFT频谱分析对比,该方法对感应电机转子断条故障诊断具有较高的诊断精度和很好的频率分辩率,能克服FFT电流频谱法主频泄漏的影响,更好地实现感应电机的转子断条故障诊断。     

无速度传感器感应电机改进转子磁链观测器

针对感应电机无速度传感器磁场定向控制系统,提出一种基于电压模型的改进转子磁链观测方法.为了有效抑制反电动势积分环节所存在的直流偏移和积分饱和问题,采用一个截止频率可根据输出频率进行自调整的低通滤波器来代替传统电压模型磁链观测器中的反电动势积分环节.然而低通滤波器的引入将会产生磁链幅值和相位的观测误差,从而导致在低速运行场合中磁链观测性能显著下降,为了解决这一问题,设计一个可以补偿磁链观测误差的补偿器.通过11kW感应电机无速度传感器矢量控制系统对所提出的改进转子磁链观测器进行了实验验证,结果证明了算法的有效性.     

Novel high-speed induction motor for a commercial centrifugalcompressor

This paper describes the electrical, mechanical and metallurgical design, construction, and testing of a novel low-cost high-speed high-efficiency induction motor to drive a new type of small centrifugal compressor in industrial cooling applications. The 28-shaft-hp 50-kr/min motor features a unique laminated rotor with a multifunction high-strength copper-alloy cage brazed with a novel process. Relatively thin high-silicon steel laminations were used to achieve low losses and high mechanical strength at low cost, Different heat treatments for the stator and rotor laminations were used to optimize the mechanical and magnetic properties, The preprototype motors achieved about 94% (electromagnetic) efficiency at the rated point, including inverter harmonics, while meeting cost (less than one-tenth of aerospace practice) and produceability goals     

感应电动机转子时间常数的离线测量方法

在感应电动机间接转子磁场定向方案中,基于电流模型的控制系统有较好的动静态特性,但电流模型却对电动机的转子时间常数非常依赖.为实现感应电动机的最优控制,给出了感应电动机转子时间常数的离线测量方法.对基于递推最小二乘(Recursive Least-Squares,RLS)算法的转子时间常数离线测量方法给出了详细分析.通过...