Analysis of Commutation of a Current Inverter Feeding an Induction Motor Load

A method for analyzing the performance of an induction motor fed from a current source inverter and especially for computing the currents during commutation of the inverter is presented. A mathematical model of an inverter-fed induction motor is given in terms of Park's vector. Based on this model a closed form time domain expression is developed for the current during commutation. The stator voltage of a current-controlled inverter-fed induction motor is shown to be almost sinusoidal with superimposed spikes during commutation of current. The computed performance of the machine is verified experimentally, and there is a very close agreement between the computed and test results. The method presented also provides information regarding the voltages across the commutating capacitors and thyristors based on which proper selection of the thyristors and commutating capacitors can be made.     

A Contribution to Tests Standardization for Inverter-Fed Asynchronous Machines

Losses of inverter-fed asynchronous motors and their experimental evaluation are considered. The formal expressions of iron and copper losses are first recalled, and it is shown as they are influenced by the harmonic content of inverter output voltages. Theoretical and experimental values of these losses are then given together with the presentation of the experimental tests used for their determination. A suitable set of tests is then suggested for the determination of the conventional efficiency of inverter-fed asynchronous motors. The content cannot be considered exhaustive on the matter. It represents only a first contributive approach to the standardization of inverter-fed asynchronous motor tests.     

An efficient braking method for controlled AC drives with a dioderectifier front end

Standard pulsewidth-modulated inverter-fed induction motor drives employ a diode rectifier bridge to supply AC power from the utility to the DC link. Although a diode rectifier is the most cost-effective solution, it does not permit reversing the power flow. This prohibits operating the machine in the regenerative braking mode for active deceleration. An innovative control method substitutes conventional hardware, such as an active front-end rectifier or a chopper controlled braking resistor in the DC-link circuit, by additional software that is implemented in the standard microprocessor control. The control algorithm maximizes the power losses in the machine and in the inverter. It enables regenerative braking operation of the induction motor at high torque. The algorithm conserves the high dynamic performance of a vector-controlled drive system     

A new approach to motor condition monitoring in induction motordrives

A new method for condition monitoring of an electrical machine is proposed. The method uses the power leads to the machine itself as the communication link between the sending station located within the machine and the receiving station located remotely outside the machine. The required communication circuit to realize data transmission in both the cases of the ordinary 60 Hz power line and the special PWM inverter-fed power line is then constructed. The communication circuit uses an asynchronous serial communication protocol and an FSK modulation for realizing frequency multiplexing in the power line. An on-line winding temperature monitoring system for an inverter-fed induction machine is constructed using this power line communication link. Experimental results demonstrate satisfactory operation of the system     

A Stator-Core Quality-Assessment Technique for Inverter-Fed Induction Machines

Localized heating caused by damage in the laminations or interlaminar insulation of the stator core increases the core losses and can lead to machine failure. Therefore, it is important to monitor the quality of the stator core for reliable and efficient operation of the machine. The methods currently available for core quality assessment are inconvenient since they require an outage and the machine to be disassembled or operated under no-load conditions. In this paper, a new method for monitoring the quality of the stator core for inverter-fed machines without motor disassembly or operation is proposed. The main concept is to use the inverter to apply a set of test signals to assess the quality of the core whenever the motor is at standstill. A set of high-frequency pulsating magnetic fields is produced using the inverter, and the power loss is observed as a function of field circumferential position to detect core problems. An experimental study on a 10-hp induction motor verifies that local interlaminar core faults can be detected with high sensitivity. The proposed technique is expected to provide a simple solution for frequent stator-core quality assessment without motor disassembly, motor operation, or additional hardware for reliable and efficient operation of inverter-fed induction machines.      

Nonlinear Adaptive Control of an Inverter-Fed Induction Motor Linear Load Case

An adaptive nonlinear control system for an inverter-fed induction motor is presented. The approach taken is fundamentally different from previous work on induction motor control in that the aim is to control shaft speed directly. Further, the inverter control variables, frequency and-voltage, are related via the steady-state model to the shaft speed and motor current. By making the controller adaptive, neither load nor machine parameters need be specified, although in practice the, latter are usually available from the machine manufacturer, and, of course, full use can be made of this knowledge.     

Identification of the machine parameters in a vector-controlledinduction motor drive

High dynamic performance of pulse-width-modulated (PWM) inverter-fed induction motor drives was achieved by using the method of field-oriented control. This method requires the actual value of the rotor time constant as essential system information, based on how the magnitude and the position of the rotor flux are calculated. An online identification technique for the rotor time constant and for other machine parameters is described. The identification is based on an evaluation of the stator current trajectory, which is the dynamic response of the induction motor to the PWM-switching sequence. An analytical machine model is operated in parallel to the actual machine, having the stator voltages and the mechanical speed of the induction motor as input signals. The coincidence of the two stator current trajectories of the model and the machine serves as an error indicator for the parameter identification scheme, permitting repetitive updates of the model parameters     

变频调速异步电动机效率优化控制的研究进展

异步电动机运行于额定工作点附近时效率较高,轻载运行时其效率会明显下降.优化变频调速异步电动机的效率对于节约能源、系统自身冷却和控制环境污染具有重要意义.总结近年来变频调速异步电动机效率优化控制策略的研究现状,包括基于模型的最优励磁控制、最小输入功率在线搜索法和最小定子电流控制等,分析了各种效率优化控制策略的性能和优缺点,指出变频调速异步电机效率优化研究的发展方向,并给出考虑电机动态响应的效率优化控制研究结果.     

SVPWM控制技术在两相异步电动机中的应用

研究了两相逆变器供电异步电动机系统的SVPWM控制技术,该系统可广泛应用于小功率、宽调速范围运行的场合。推导并建立了两相异步电动机的数学模型,分析了两相逆变器驱动两相异步电动机的工作原理和空间矢量的时间分配原则。以一台小功率两相异步电动机为对象,进行了系统仿真,给出该电机采用SVPWM方式控制运行时的仿真波形。     

Control Characteristics of Inverter-Fed Induction Motor

Efficient use of an inverter-fed induction motor drive necessitates a knowledge of the characteristics of the induction motor from a " control" point of view. The characteristics of both the voltage -and the current-source inverter-fed induction motor drive are investigated, neglecting the filter time constants in the link and feedback loops. Of particular interest is the role played by the voltage/current and frequency inputs. Their effects on variables that are not often discussed such as torque angle, stator real power, airgap flux- linkages and stator and rotor voltages/currents are studied. A by- product of this aspect of the study leads to the nature of feedback signals and their suitability for control purposes. It is also found that the link filter has little effect on relative suitability of these signals. A study of the current source induction motor drive dynamics for torque angle feedback is included.     

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...     

Computation of Core Losses in Electrical Machines Using Improved Models for Laminated Steel

Two new models for specific power losses in cold-rolled motor lamination steel are described together with procedures for coefficient identification from standard multifrequency Epstein or single sheet tests. The eddy-current and hysteresis loss coefficients of the improved models are dependent on induction (flux density) and/or frequency, and the errors are substantially lower than those of conventional models over a very wide range of sinusoidal excitation, from 20 Hz to 2 kHz and from 0.05 up to 2 T. The model that considers the coefficients to be variable, with the exception of the hysteresis loss power coefficient that has a constant value of 2, is superior in terms of applicability and phenomenological support. Also included are a comparative study of the material models on three samples of typical steel, mathematical formulations for the extension from the frequency to the time domain, and examples of validation from electrical machine studies.     

非正弦激励时变频电机铁耗计算方法研究

针对变频电机铁耗分析中存在的铁磁材料建模,非正弦激励时铁耗计算模型等问题,结合近年来为解决这些问题所提出的理论和方法进行了系统地综述和分析,指出了现有各种方法的优缺点,并提出了今后变频电机铁耗分析的研究方向.     

The Influence of Inverter Feeding on the Apparent Stray Inductance of Asynchronous Machines

The stray inductance is an important parameter for the design of inverters feeding asynchronous machines. Measurements are proposed which are relevant for determining the apparent stray inductance of an inverter-fed asynchronous machine. These measurements show that the apparent stray inductance is considerably smaller than the one obtained with classical sinusoidal methods. This amounts to smaller commutating capacitors in current source inverter (CSI) motor drives. A theoretical explanation for this phenomenon is presented and confirmed by calculation.     

On the variation with flux and frequency of the core loss coefficients in electrical machines

A model of core losses, in which the hysteresis coefficients are variable with the frequency and induction (flux density) and the eddy-current and excess loss coefficients are variable only with the induction, is proposed. A procedure for identifying the model coefficients from multifrequency Epstein tests is described, and examples are provided for three typical grades of non-grain-oriented laminated steel suitable for electric motor manufacturing. Over a wide range of frequencies between 20-400 Hz and inductions from 0.05 to 2 T, the new model yielded much lower errors for the specific core losses than conventional models. The applicability of the model for electric machine analysis is also discussed, and examples from an interior permanent-magnet and an induction motor are included.     

高速长定子直线感应电动机的建模与仿真

从高速长定子双边直线感应电动机(double-sided linear induction motor,DSLIM)的基本原理出发,利用直线电动机的发射曲线和数学模型,采用动子磁场定向的控制原理,在Simulink环境下,建立了电机的数字仿真模型。用该模型分析电机的动态性能,得到了该类型电机的发射曲线以及电机电压、电流、压频比、功率因数、功率效率、能量效率等参数的变化规律,为脉冲供电系统和驱动系统的设计提供了重要的参考依据;利用该类型电机可以实现对大质量物体的发射。仿真结果与基于ANSOFT二维瞬态场计算的结果吻合较好,验证了该模型的正确性。仿真模型具有运算速度快、简单易行等优点,为该类电机控制策略的研究及具体实现提供了新的途径。     

空间矢量脉宽调制在二相异步电动机变频调速中的应用

研究了二相逆变器-异步电动机系统的空间矢量脉宽调制(SVPWM)控制技术。该系统可以广泛应用于小功率、宽调速运行的场合。通过对电机基本方程进行Kron变换,建立系统完整的数学模型,提出四个电压矢量八个工作空间的SVPWM控制技术,推导控制参数和计算公式,建立了基于80C196KC控制器的二相逆变器-异步电动机系统。实际运行表明,SVPWM在二相异步电动机变频调速中的应用可使转矩脉动减少、效率提高,具有一定的经济性和实用性。     

Study of Parameter Sensitivity in High-Performance Inverter-Fed Induction Motor Drive Systems

Vector control schemes are used in inverter-fed induction motor drives to obtain high performance. Crucial to the success of the vector control scheme is the knowledge of the instantaneous position of the rotor flux. The position of the rotor flux is measured in the direct scheme and estimated in the indirect schemes. Since the estimation of the flux position requires a priori knowledge of the induction motor parameters, the indirect schemes are all machine-parameter dependent. Changes in temperature and saturation levels of the machine vary the machine parameters and, hence, indirectly influence both the steady state and the dynamic operation of the drive system. Analytic expressions are derived to evaluate the effects due to parameter sensitivity. The simulation is experimentally verified on a drive system.     

Effect of crosspath resistance between adjacent rotor bars onperformance of inverter-fed high-speed induction motor

The effects of crosspath resistance between adjacent rotor bars on steady state performance of inverter-fed high-speed cage induction motors are discussed. It is 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 and the slip. The steady state characteristics of the high-speed induction motor drives for various crosspath resistance are discussed on the basis of theoretical and experimental results. The results of this research are applied in the design of a high-speed induction motor with uninsulated rotor bars     

笼型转子无刷双馈电机等效电路及电磁转矩

无刷双馈电机是一种性能优良的新型感应电机。经过频率和绕组归算得出笼形转子无刷双馈电机的通用等效电路。等效电路对电动状态和发电状态都适用。在此基础上，得出了双馈电机在自然同步和异步特殊运行模式下的等效电路，然后根据等效电路得出了电磁转矩计算公式。它利用了最新的笼形转子无出线电流检测技术。