ANALYSIS AND CONTROL OF TORQUE PULSATIONS IN CURRENT FED INDUCTION MOTOR DRIVES

ABSTRACT

Three types of feedback compensation schemes are described which can be used to reduce the torque pulsations which normally occur when induction machines are supplied from a current source inverter. The approach is verified both by a detailed computer simulation and also by test results from an actual system. Limitations of the method near zero slip frequency (no load) is discussed and a means suggested for elimination of the problem.     

一种改进的感应电机最大效率控制技术研究

在分析感应电机最大效率控制技术基础上，提出了两项改进措施。首先针对传统方法搜索慢，收敛性能差的缺点，提出了一种混合搜索技术，即通过电机损耗模型离线计算励磁电流设定值的下限，采用黄金分割法在已经缩小的范围内进行搜索；其次针对搜索过程中转矩脉动问题，提出了一种转矩电流前馈补偿方案。为了获得良好的暂态响应，在转矩或者设定速度发生改变时，励磁电流重新恢复到额定值，详细的切换方案也被提出。实验和仿真验证了方案的实用性和有效性。     

逆变器供电感应电机稳态性能仿真的研究

建立了考虑转子集肤效应和非线性因素的逆变器供电感应机电的数学模型与仿真模型,为提高仿真精确度,对稳态仿真方法进行了研究。对交流传动系统的仿真结果与实验结果进行了比较,效果较为满意。     

PWM逆变器驱动异步电动机采用长线电缆时电压反射现象的研究

PWM逆变器驱动的异步电动机,在逆变器和电动机之间采用长线电缆传输时,会产生电压反射现象,导致在电动机端产生过电压,高频阻尼振荡,使电动机绝缘老化,造成电动机在短期内绝缘击穿等事故,这是PWM逆变器驱动异步电动机采用长线电缆所产生的负面效 应,文中首先分析了长线电缆传输时由于长线电缆的分布参数所产生的电压反射现象及其所造成的过电压等负面效应,分析表明电动机端产生的过电压与逆变器输出PWM脉冲上升时间和电缆长度有关。PWM脉冲上升时间愈短,电缆愈长,反射现象愈明显。采用低成本无源滤波技术可消除这种负面效应,文中分析和设计了一种一阶RC电动机端滤波器,用于接在异步电动机的接线端上,实验结果表明该滤波器可有效地减少电动机端过电压等负荷效应,从而提高系统的可靠性。     

利用延迟反馈进行异步电动机混沌反控制

目前已有实验证明，某些系统在混沌运动下可获得更好的效果。因此，具有混沌运动特性的电机传动系统成为新的研究热点之一。本文探讨了通过延迟反馈控制对异步电动机传动系统进行混沌反控制的技术，实现了将异步电动机的稳态由通常的固定在某个转速控制到周期的甚至混沌的运动。本文分析了应用延时反馈控制实现异步机混沌运动的原理，给出了仿真实现和分析。     

A NUMERICAL APPROACH FOR THE ANALYSIS OF INVERTER-FED INDUCTION MOTOR SCHEMES

ABSTRACT

The steady-state analysis of an induction motor when fed from a voltage-source inverter for varied types of operation using a numerical approach is presented in contrast to the existing theories such as instantaneous symmetrical component transformation and the state-variable technique. This approach has the added advantage over that of the state variable technique in that there is no change in the elements of the machine-matrix when more than one state exists, in addition to that of obtaining directly the nature of variation of currents, voltages and torque with respect to time.     

VOLTAGE-CONTROLLED 60 HZ LINEAR INDUCTION MOTOR DRIVES

ABSTRACT

A study has been conducted to evaluate design parameters of mobile-primary linear induction drives with variable-voltage fixed-frequency (WFF) excitation. This mode of drive is considered potentially viable for certain transit operations, such as inter-terminal airport shuttles. Each vehicle would pick up 60 Hz three phase AC, and the LIM thrust would be adjusted by an on-board phase-controlled thyristor power conditioner. This mode of operation is considerably simpler than the inverter-fed variable-voltage variable-frequency (VWF) LIM drive, but results in an appreciable increase in the required kVA rating of the power conditioner. Design studies have been conducted for both aluminum-capped and solid-steel reaction rails, using computer models validated by large scale test data. An evaluation of rail heating has shown that the temperature rise of an aluminum cap can be very high under WFF conditions, and a solid-steel rail is recommended for fixed-frequency transit applications.     

SPEED AT BREAKDOWN TORQUE OF A SINGLE-PHASE INDUCTION MOTOR

ABSTRACT

The purpose of this paper is to present an “exact” analytical expression to calculate speed at breakdown torque and the breakdown torque of single-phase induction motors. From the theoretical expression for torque developed by a single-phase motor, a sixth order polynomial in speed at breakdown torque is obtained, and solved, using a well known method. A real root for per unit speed, i.e. the ratio of speed to the synchronous speed, that lies between 0 and 1 is selected and the actual breakdown torque is determined by substituting it in the torque equation. The breakdown torque, also termed as maximum torque, so obtained has been found to yield better correlation between the predicted and the tested results than the only existing empirical relation. Steps to calculate speed at maximum torque are also suggested. For an arbitrarily selected single-phase induction motor, a curve of speed at breakdown torque as a function of r₂/X is also included for the purposes of illustration and understanding.     

CALCULATION OF PITCH TORQUE FOR AN ARC-TYPE LINEAR INDUCTION MOTOR

Abstract

An adaptation of Parseval's theorem is used to compute the pitch torque produced in an arc-type single-sided linear induction motor, directly from the Fourier transforms of the air gap magnetic field components. Results predicted through this approach are shown to agree favourably with measurements made on a 2-m diameter test wheel facility.     

PERFORMANCE ANALYSIS OF A HIGH STARTING TORQUE SINGLE-PHASE INDUCTION MOTOR

ABSTRACT

The objective of the work described is to make an assessment of the possible use of three-phase induction motor working as a single-phase motor. The analysis is performed on the proposed winding arrangement, introduced previously by same authors. The analysis includes all motor windings, whereas the conventional analysis is performed on the running winding only. The motor windings are analyzed through the stationary direct and quadrature axes. The magnetic field and E.M.F's of the motor are studied at starting, run-up and running operation. Hence, d-q axis equivalent circuits are deduced to represent the motor at different modes of operation, taking into consideration the core losses and sturation effects. Prediction of the run-up and running characteristics of the motor under investigation is achieved by solving the equations of equivalnet circuits in a simple manner. The predicted results are compared with the releavant experimental results. Good agreement has been achieved, and this confirms the validity of proposed analysis.     

异步电动机直接转矩控制系统的改进方案

针对基于直接转矩控制的异步电动机运行时存在较大的电流及转矩脉动问题，该文提出一种新的控制方案。该方案是在原来两电平逆变器的基础上增加一个Boost电路，以使异步电动机的电流及转矩脉动减小，并且使变频器开关频率降低。仿真结果表明该方法案能有效地解决电流及转矩脉动的问题。     

一种感应电机直接转矩控制系统性能改善方案

该文首先从理论上对数字化控制感应电机传动系统的性能进行了推导，对电机转矩的变化量进行了详细的分析。然后结合直接转矩控制的原理，提出了一种新型的控制方案。从仿真结果可以看出：不仅系统的动态响应依然很快，而且可以有效地改善稳态转矩脉动较大的情况：同时由于采用了空间电压矢量调制，稳定了逆变器的开关频率。     

THE EFFECTS OF TORSIONAL ELEMENTS ON THE TRANSIENT PERFORMANCE OF LARGE INDUCTION MOTOR DRIVES

ABSTRACT

In the modelling of induction motor drives it is common to choose only a first order representation of the torsional elements of the motor drive. When there is a requirement for more detailed information on the behaviour of the torsional elements of the drive a method of analysis is often chosen which inherently suppresses the important features of interaction between the torsional elements and the drive motor. This can lead to completely erroneous results as to the level of transient torques seen at various points in the drive during faults or switching operations. The analysis is often further simplified by the neglect of mechanical system non-linearities, the most important of which are backlash and torsional couplings having non-linear stiffness versus deflection characteristics. The paper discusses the basic modelling problem and highlights the differences in computed responses obtained when using mechanical system models of varying complexity. The practical implications of this topic are highlighted by examining the behavior of a power station circulating water pump and the practical problem areas are stressed. Comparisons of dynamic torque-slip curves for the drive motor with a single inertia representation of the mechanical load and those obtained with more complex modelling are shown     

改进的直接转矩控制在异步电动机中的应用

该文提出了一种改进的直接转矩控制方案并应用于异步电机控制系统中。其不仅结构简单，而且性能可与传统的磁场定向控制相媲美。一个简单的转矩控制器代替传统的三态磁滞比较器用来保持恒定的开关频率，一个稳态工作的简单补偿器用于补偿电压模型中定子磁链估计的数值和相位误差。试验和仿真结果表明，该文提出的补偿方案取得了良好的控制效果，其在保持直接转矩控制的传动结构更为简单的同时，还大大提高了整个控制系统的性能。     

TORQUE AND CURRENT STRESS OF A THREE-PHASE INDUCTION MOTOR DUE TO NON-SIMULTANEOUS SWITCH-ON

ABSTRACT

The paper discusses; the ways for affecting the current and torque surges originating due to non-simultaneous switch-on of feeding phases to a 3-phase induction motor. Here, the non-simultaneous switch-on is defined to be that during which at first two phases are switched on (at an instant defined with respect to the time course of voltage) and only then, with some delay, the switch-on of the third phase follows. The paper demonstrates that -when compared to a simultaneous switch-on of all 3 phases- proper control of non-simultaneous switch-on as defined above can reduce both the motor impact stress and the current surges substantially. However, unproper successive switching-on may increase these unwanted phenomena. First, the present contribution brings an analytical solution for current and torque at zero revolutions and then, in the latter part, the influence of the controlled switch-on motor start is discussed.     

基于新型定子磁链观测器的直接转矩控制

文中提出一种基于转子位置的面贴式永磁同步电动机的定子磁链估计方法。该方法从转子的位置信息和定子电流预测定子的磁链。给出了磁链观测器的数学模型，并在空间矢量调制直接转矩控制（SVM-DTC）策略中对该磁链观测器与常规电压积分式观测器进行了比较研究。仿真与实验结果表明，采用该观测器的SVM-DTC可以在2％-100％额定转速内稳定运行，电流波形畸变小，转矩性能优越，而采用常规电压积分式观测器的SVM-DTC在转速低于15％额定转速已不能稳定运行。     

永磁无刷直流电机磁阻转矩的解析计算方法

该文利用许－可变换，构造了考虑齿槽效应的等效气隙磁导函数，结合偏微分方程的解析算法，计算出等效气隙内任意半径上的气隙磁通密度分布，由此提出了一脉永磁无刷直流电机磁阻转矩的解析计算方法，其计算结果与有限无计算结果对比，转矩波形基本吻合，证明此方法是正确的，可靠的，同时该方法可应用于磁阻转矩的计算，为永磁无刷直流电机设计和优化提供了基本分析手段。     

OPTIMAL STATE FEEDBACK CONTROL OF A CURRENT SOURCE INVERTER-FED INDUCTION MOTOR DRIVE USING A NEW ROTOR CURRENT OBSERVER

ABSTRACT

ABSTRACT The design, implementation and performance of a multivariable optimal state feedback controller for a Current Source Inverter-fed Induction Motor (CSI-IM) drive using a new reduced order observer to estimate rotor currents have been reported in this paper. A quadratic performance index together with a set of prescribed closed loop eigenvalues for placement are considered for application to a d-q axes state space linearized model of the drive to derive the control law - for achieving prescribed degree of stability in contrast to an earlier design with only pole-placement. The optimal control law derived is a function of all the states, the inaccessible states like d-q axes rotor currents being estimated by a new observer whose structure is simpler than that of one used in an earlier case. The controller-observer is implemented using an inexpensive microprocessor kit and the experimental results are presented along with the digital simulation results for the controlled drive to show its performance under step changes of load torque and references.     

基于感应电机启动电磁转矩Hilbert-Huang变换的转子断条故障诊断

该文提出了一种感应电机转子故障诊断新方法。当感应电机转子出现断条故障时，转子绕组的不对称将会使电磁转矩谱中引入2sfs(s为转差率，fs为电网频率)谐波分量。利用砌bert-Huang变换中经验模态分解(EMD)方法对启动电磁转矩信号进行了分解，得到若干本征模态函数(IMF)。通过计算包含故障信息的IMF分量的瞬时频率，可以检测出转子断条故障。同时，根据包含故障信息的IMF的幅值可以进一步判断出转子断条根数。实验结果证明该方法是可行的。     

EFFECT OF SKEWING ON THE COGGING TORQUE IN INDUCTION MACHINES

ABSTRACT

This paper presents a simplified method to predict the cogging torque in induction machines including the skewing effect An equivalent circuit including die effect of both slot harmonics and rotor skewing is developed. A special attention is paid to study the skewing effect on the machine behaviour especially at starting instant. Moreover, the leakage reactance due to the skewing is calculated using the suggested method. Useful conclusions are given at the end of this paper which is thought of good use and valuable for both designers and users of squirrel cage induction motors.