ANALYSIS OF A SERIES-DELTA CONNECTED TANDEM INDUCTION MOTOR

Abstract

A tandem induction motor comprised of two independently housed stator windings, one housing stationary and the other able to be physically rotated, and a squirrel-cage rotor common to both stators is described. When the motor is fed from a single source, altering the position of the moveable stator changes shaft speed in a similar manner to operating a normal induction motor at variable terminal voltage

This paper presents an equivalent circuit model of the tandem induction motor for series-delta connected stator windings. Using the equivalent circuit stator current, power factor, and torque are calculated and then compared to laboratory test results obtained from a 3 kW tandem motor test rig     

TRANSIENT RESIDUAL VOLTAGE ANALYSIS DURING ISOLATED OPERATION OF A GROUP OF INDUCTION MOTOR LOADS

ABSTRACT

The bus transfer schemes are provided in emergency switchgears feeding critical duty auxilary loads in process plants and thermal/nuclear power plants. During the time of bus transfer, group of such loads gets isolated from power supply. Transient residual voltage analysis of such loads, mainly consisting of induction motors loads, plays a vital role in deciding the transfer scheme. This paper reviews some of the existing machine models and solution techniques suggested for predicting the voltage transients during isolated operation of induction motors and reports a new solution algorithm based on a non iterative scheme for the multimachine case. The new solution scheme is found to be more reliable and faster than the existing scheme. The theoretical results using various models have been compared for single as well as multimachine cases. The practical validity of various models have been studied by comparing the theoretical results with actual test results obtained in laboratory.     

基于瞬态模型的不对称供电三相感应电动机分析

三相电压不对称对感应电动机性能影响较大，本文建立了三相感应电动机瞬态模型，基于该模型和复数不平衡因数（CVUF)的概念，研究不对称供电电压对感应电动机性能的影响，对不对称三相电压供电感应电动机起动过程进行了仿真，计算了不同CVUF时感应电动机的起动过程，研究了起动过程中的峰值转矩，起动时间、达到稳态后的三相电流不平衡因数，转速，转速波动，转矩波动与CVUF的关系，得出了相应结论。     

DESIGN OF VARIABLE SPEED INDUCTION MOTOR DRIVE WITH A CURRENT-FED INVERTER

ABSTRACT

A closed-loop speed control scheme with reversing and regenerating capability for a squirrel-cage induction motor is described. The scheme makes use of a fully-controlled bridge for a.c. to d.c. conversion, a currend-fed inverter for generation of variable frequency a.c. supply for motor and an analogue tachogenerator for speed feedback signal. The current-reference signal is generated by a novel slip calculator. This paper describes the slip calculator and the design of controllers based on an approximate model of motor. Experimental results validating the methods used for design of controllers are also presented.     

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。     

用Bergeron法计算变压器线圈暂态电压分布

本文提出了变压器线圈电磁暂态分析的新方法－Ｂｅｒｇｅｒｏｎ法，推导了有互感电路的等值参数和计算公式，叙述了如何形成节点导纳矩阵。实测结果与分析表明，在变压器低压线圈短路时，高压线圈与空心线圈的电感相同。根据计算与实测结果分析，提出了确定等值电路中各项参数的方法。     

基于适应性遗传算法的滑模控制感应电机伺服驱动系统研究

根据感应电机伺服系统高精度、快响应的要求,以及传统的滑模变结构控制器涉及较多的参数和逻辑判断次数等缺点,设计了一种简化的滑模控制律,并用Lyapunov稳定性理论证明了控制系统的稳定性,然后利用自适应遗传算法优化滑模控制律中涉及的参数,得到控制器最佳的参数组合.试验结果表明：该控制策略不仅有效地减小了滑模控制的抖振,且大大提高了系统的快速响应能力,系统具有较好的动、静态性能以及抗干扰能力.控制策略具有设计过程简单、意义清晰等优点,对于高精度、快响应的感应电机伺服系统,它是一种有效的实时控制策略.     

INDUCTION MOTOR DRIVE STABILIZATION WITH STATOR CURRENT FEEDBACK

ABSTRACT

The use of state feedback to control Induction motor drive systems is examined. Using the machine currents and speed as the system states, a general linearized formulation of the problem is derived. This formulation has the advantages of previous forms based on complex variable analysis, but is not subject to the limitations of that method.

The proposed model Is used to study machine control with stator current feedback. The results show that stator current feedback can be used to improve the dynamic characteristics of the drive system. Comparisons of stator current control with the uncontrolled machine and with the slip controlled machine are presented over the range of operating speed, load, and inertia. In all cases, advantages of current controlled operation can be seen.     

ANALYSIS OF CONVERTER CONTROLLED DC SERIES MOTOR. II. TRANSIENT ANALYSIS

ABSTRACT

The steady state and transient analysis methods of converter-fed dc series motor reported so far do not take into account the nonlinearity of the magnetic circuit. Furthermore for transient analysis discontinuous conduction has been neglected and only first order model has been reported though series motor is essentially a second order system.

Various approximations for the nonlinearity of the magnetic circuit and steady state analysis have been described In Fart I of the paper. The present paper (Part II) describes the methods of transient analysis for fully-controlled and half-controlled converter controlled dc series motor taking the nonlinearity and discontinuous conduction into account. First order as well as second order models have been considered. Calculated performance has been verified experimentally.     

PERFORMANCE ANALYSIS OF LOAD COMMUTATED INVERTER FED CAGE INDUCTION MOTOR DRIVE

ABSTRACT

An approach, to analyse the performance of a variable speed cage induction motor drive fed from load commutated inverter (LCI), is presented. Induction motor with an appropriate capacitor across its stator terminals constitutes the load on the inverter. A fully controlled bridge converter, supplied by a variable dc voltage source, commutated with the back emf of the motor, acts as an inverter. An algorithm to compute the motor performance, is developed using equivalent circuit representation of the system. Strategies for the selection of control variables, in order to achieve the desired speed range for satisfactory performance of the drive are given. The performance of a 3-hp, cage induction motor fed from LCI is computed, using the developed algorithm for wide range of speed; and is verfied experimentally.     

计及感应电动机负荷的静态电压稳定性分析

该文建立计及感应电动机机电暂态过程的单负荷无穷大系统的小干扰电压稳定分析数学模型，分析了感应电动机负荷参数变化对小干扰电压稳定性的影响。以简单系统为例，说明了基于潮流模型的静态电压稳定指标的共同物理本质，文中通过不同感应电动机负荷参数的小干扰稳定分析和时域仿真，对基于潮流模型的静态电压稳定指标进行了准确性分析。分析结果表明：以前基于潮流模型的静态电压稳定指标忽略了电力系统的动态负荷因素，其指标认为是电压稳定的系统却可能发生电压失稳，因此，基于潮流模型的静态电压稳定指标是不准确的。该文提出的小干扰电压稳定分析数学模型是电压稳定的一种简化分析，在实时等值系统的基础上具有在线应用的前景。     

ANALYSIS OF A SPHERICAL INDUCTION MOTOR

Abstract

The advent of robotics and automated manufacturing processes has brought about an urgent need for novel electromechanical transducers with unusual design and performance characteristics. Operating flexibility, ruggedness, size, force to weight ratio, and robust control capabilities are design attributes which place a heavy burden on conventional machines used for manipulation purposes. The spherical induction motor introduced in this paper is an electromechanical drive which holds considerable promise in these application areas. A general analysis of both the fields and resultant forces generic to the spherical induction motor is presented. The analysis properly accounts for the diffusion of the magnetic field with changing frequency and motor speed. To aid in the prediction and conceptualization of the torque and commensurate motor losses, normalized plots of these parameters are given for various limiting values of skin depth ratio to conductor thickness. The analysis concludes with a prediction of terminal relations for a typical 3-phase winding. After predicting stator phase inductances (self, mutual, and rotor speed components), a mechanism for predicting rotor speed is discussed. Results indicate that the device is capable of continuous speed control and efficient torque production.     

TRANSIENT ANALYSIS OF BRAKING MODE OPERATION OF INDUCTION MOTOR FED FROM A VARIABLE FREQUENCY SOURCE

ABSTRACT

The transient behaviour of a three phase induction motor in the braking mode is investigated when the motor is fed from a variable frequency source. Appropriate voltage and frequency conditions to ensure minimum stopping time for plugging as well as for the case when plugging is used in conjunction with regenerative braking are identified. A dynamic model has been developed using the theory of instantaneous symmetrical component and associated operational equivalent circut and therefrom the transient performance of the motor in both the cases are compared with that of the normal plugging.     

A NEW APPROACH TO PERFORMANCE ANALYSIS OF CHOPPER CONTROLLED D.C. MOTOR DRIVE

ABSTRACT

An analytical method for performance analysis of a d.c. separately excited motor fed from a chopper is presented. The motor input voltage is represented as a series of step-voltages with a time phase difference. The system equations are solved to obtain closed-form solutions for motor current and speed, for transient as well as steady state conditions. The method presented is superior to existing methods in that the solution is in closed-form, and does not make recourse to recursive numerical techniques. The solutions for steady state condition corresponding to any set of operating conditions (voltage, chopper duty factor, load torque) can be directly obtained. The computational effort and time needed is therefore extremely small as compared to other methods.     

NUMERICAL ANALYSIS OF TUBULAR INDUCTION MOTOR WITH COMPOSITE ROTOR

ABSTRACT

A numerical solution is presented for the fields and forces in tubular induction motor having a rotor consisting of alternate rings of copper and steel mounted on a solid steel core when excited by a sinusoidally distributed current sheet. The edge effect due to the finite length of the current sheet and the inhomogeneity in the rotor material are taken into consideration.

The numerical solution of the field problem is obtained using the finite difference technique. The field equations are formulated in terms of the magnetic vector potential. The corresponding difference equations are derived for the different media, different surface boundaries and the different corner nodes.

The magnetic vector potential distribution, the flux density distribution and the generated force for different values of copper to steel ratio in the rotor are computed. The computed results are compared with the experimental results published by the authors [ 4 ].     

ANALYSIS AND CHARACTERISTICS OF THE DISK-ROTOR INDUCTION MOTOR

ABSTRACT

The induction motor with an axial air gap and a flat homogeneous disk-rotor shows some performance characteristics that are superior to conventional induction machines. Large rotational speeds and small moments of inertia promise high power densities and small mechanical time constants. This paper presents an analytical model which includes the two-dimensional current distribution in the secondary, thus extending a previous simplified treatment. The model also accounts for fringing phenomena and can handle a secondary with a radius-dependent thickness and conductivity. Numerical results for the local distributions of field, current density, and forces; a typical torque-speed characteristic; a current locus; and an equivalent circuit are presented and serve as a basis for discussion and comparison.     

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。     

感应电动机暂态电压失稳的定量分析

用时域仿真重现了感应电动机负荷引起的暂态电压失稳现象，进一步改进了感应电动机暂态电压稳定的判据，以便尽早地中止仿真过程；还提出了暂态电压稳定裕度的概念和定义，直接求取与暂态电压稳定相应的故障临界切除时间，以及与给定故障切除时间相应的极限动态负荷。算法的有效性和强壮性华中系统、浙江系统和新英格兰系统中得到了验证。     

HIGH SPEED INDUCTION MOTOR DRIVE WITH ACTIVE MAGNETIC BEARINGS AND SLIDING MODE DECENTRALIZED CONTROL

ABSTRACT

Active magnetic bearings are credited with high performance in terms of low energy consumption, high speeds, increased reliability and low maintenance costs.

This paper discusses a high-speed induction motor with active magnetic bearings: both radial and axial. The decentralized control system of active magnetic bearings is based on sliding mode variable structure principle to provide robustness to parameter detuning and perturbations.

Test results on a laboratory model of 300 W and 25000 rpm motor designed and built for the scope are very promising for applications to high speed machine tools, vacuum pumps etc.     

不对称阻尼绕组凸极同步电机瞬态及超瞬态参数的分析与计算

现代凸极同步电机转子阻尼绕组结构设计比较灵活，除通常对称等节距阻尼绕组外，还有对称不等节距绕组和不对称、但以二极电机为周期循环的阻尼绕组。该文以不对称、但以二极电机为周期循环的阻尼绕组的同步电机模型作为研究对象，对阻尼绕组按实际的网形电路选取回路，从派克方程出发，获得该模型的磁链方程和电压方程，经由dqo变换及一些技巧性处理，导出运算电抗xo(s)和xq(s)，然后经参数辩识，确定电机的直、交轴瞬态电抗和超瞬态电抗以及相应的时间常数。该文方法不但适用于不对称、但以二极电机为周期循环的阻尼绕组，也适用于等节距和不等节距的对称阻尼绕组。该文提供的是计算凸极同步电机暂态参数的一种新方法。