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。     

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.     

DESIGN OPTIMIZATION OF CURRENT SOURCE INVERTER FED SQUIRREL CAGE INDUCTION MOTOR

ABSTRACT

This paper deals with the design optimization of current source inverter (CSI) fed squirrel cage induction motor. For this a set of ten independent variables is selected and seven objective functions are considered namely, the active material cost, operating cost, a mixed objective function of the active material cost and operating cost, torque pulsations, voltage across commutating capacitor, maximum commutation time of CSI and an integrated objective function. To visualize extreme performance for a particular objective function, the design is optimized considering only one objective function at a time. Finally an integrated objective function is proposed which is formed as a combination of all other objective functions with suitable weighting factors to suit optimum design for a particular application. In the task of design optimization the desired thermal, starting and normal operating performance are optimally met by imposing twelve suitable constraints. In this investigation the Sequential Unconstrained Minimization Technique (SUMT) with interior penalty function approach is used to optimize the design. In this method, Rosenbrock's method is used to achieve unconstrained minimization. The optimized design results of a 7.5 kW, delta connected CSI fed cage motor are given and discussed in detail.     

基于DSP的交流电动机变频调速控制系统

本文介绍了一种基于DSP交流电动机VVVF控制系统设计方案，采用SVPWM控制策略，具有过调制功能，当母线电压波动时，能使PWM波形输出稳定，实验波形显示系统具有较好的性能。     

高压变频调速中LC滤波电容与异步电机之间的自激

对发生自激时变频装置的滤波器和异步电机的单相等值电路进行分析，推导出自激时LC滤波电容与异步电机频率及电机参数的关系。建立变频装置驱动空载异步电动机JSQ 157－8的仿真系统，通过对封锁脉冲后自激现象的观察，分析了自激幅度与电机参数、滤波电容以及直流电容电压等的关系。仿真结果与正在研制的变频装置脉冲封锁后发生自激的实验结果吻合，表明理论分析与仿真计算正确。最后提出了LC滤波器参数选择及其避免自激的措施。     

APPROXIMATE ANALYSIS OF TEMPERATURE RISE IN AN INDUCTION MOTOR DURING DYNAMIC BRAKING

ABSTRACT

The problem of two-dimensional transient heat flow in the stator of induction motor is solved by use of a finite element formulation and arch-shaped elements in the r-θ plane of the cylindrical co-ordinate system. The shape functions and exact solution matrices are derived algebraically for utmost economy in computation. The temperature distribution has been determined considering convection from the stator frame and cylindrical airgap surface. Finally the temperatures obtained by this two dimensional approximation have been compared for different stator currents considering the time required for each stator current during the transient.     

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.     

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.     

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.     

PERFORMANCE AND ANALYSIS OF CHOPPER FED D.C. SERIES MOTOR UNDER REGENERATIVE BRAKING

ABSTRACT

The paper presents a method of analysis and performance of chopper fed dc series motor under regenerative braking. The method of analysis takes into account the nonlinearity of the magnetic circuit, armature reaction, effect of commutation pulse and source inductance. Equations have been derived for the calculation of (a) machine speed-torque characteristics (b) regenerative power and efficiency of regeneration, and (c) current ripple and filter inductance value. The method also shows the prediction of stability at low speeds and conditions for failure of regeneration. The effects of chopper operating frequency, source inductance, commutation capacitor and input-filter capacitor on regenerative power and efficiency of regeneration, and stability of braking have been described. Theoretical deductions have been verified experimentally     

PERFORMANCE AND ANALYSIS OF CHOPPER FED D.C. SEPARATELY EXCITED MOTOR UNDER REGENERATIVE BRAKING

Abstract

A method is presented here to analyse the performance of a separately excited d.c. motor under regenerative braking mode and provides a technique to select the necessary inductance to reduce the ripple in the armature current as well as to eliminate the discontinuous conduction of the armature current and to optimize the regenerative power. The effect of armature reaction and also that of chopper commutation interval have been taken into account. The calculated performance agrees very closely with the experimental results.     

TRANSIENT AND STEADY-STATE ANALYSIS OF A VOLTAGE CONTROLLED INDUCTION MOTOR DRIVE WITH DELTA CONNECTED WINDINGS

ABSTRACT

This paper deals with the transient and steady-state analysis of a voltage controlled induction motor (VCIM) drive with delta connected windings. Symmetrically triggered back-to-back connected thyristor pairs are used in each of the three lines to effect change in terminal voltage. Using a three-phase stator side equivalent circuit of the induction motor, the state equations for different modes of operation are formed and solved using a digital computer. The results of the transient and steady-state analysis for a specified triggering angle and load torque are presented and compared with those for a wye connected motor.     

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.     

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     

DIGITAL SIMULATION OF A CURRENT SOURCE INVERTER FEEDING AN INDUCTION MOTOR

Abstract

A new digital simulation model of the auto sequentially communicated inverter supplying an induction motor is presented. All normal and abnormal operations of the system can be accurately described by this model. Moreover, all the possible behavior modes occurring during the above operations can be predicted without describing each particular circuit configuration, as it was in previous digital simulation approaches. The computer running time concerning with several simulations makes the proposed method a useful tool comparable to analog techniques in order to study such a system     

RELATIVISTIC PLANE WAVE ANALYSIS OF A CARTESIAN INDUCTION MOTOR STRUCTURE

ABSTRACT

Analysis of electrical machinery is usually carried out with the aid of lumped-parameter techniques; at the same time, a distributed-parameter model is of theoretical interest as it provides insight into the behavior of the magneto-electric device without any restriction imposed upon supply frequency, width of air gap or even velocity.

An analysis which takes into account the finite velocity c of a plane electromagnetic wave in vacuum, of necessity resorts to restricted relativity, which has the great advantage of leaving the field equations form-invariant.

In the present paper such an approach is briefly outlined.     

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.     

THE INFLUENCE OF THE INDUCTION MOTOR VELOCITY ON THE TRANSIENT PHENOMENA

ABSTRACT

The paper deals with transient phenomena of an induction motor caused by a voltage pulse at different angular velocities. The response of the machine varies according to the angular velocity. The dependence of the time constants on the angular velocity has been derived. The response can be an exponential one or aperiodically damped. The reasons why the electromagnetic transient phenomenon of an asynchronous motor at standstill lasts longer than while revolving are explained. Per Unit System and space vectors are used.     

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.     

TRANSIENT ANALYSIS OF CONVERTER-CONTROLLED DC SEPARATELY EXCITED MOTOR

ABSTRACT

Three methods of transient analysis of a de separately excited motor controlled by a phase-controlled converter have been derived. These methods are compared with regard to accuracy, computation time and usefulness.