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 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.     

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.     

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.     

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.     

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 ].     

计及感应电动机静态特性的PV曲线分析

采用变导纳法将感应电动机的静态等值参数直接运用于电力系统PV曲线的计算。该方法能够准确地描述感应电动机的静态特性,并易于实现。同时分析了感应电动机失稳对PV曲线和静态电压稳定的影响,并提出了一种临界点选择的方法。     

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.     

多层理论在圆筒型直线感应电动机计算上的应用

本文从麦克斯韦方程出发，在圆柱坐标系下建立了圆筒型直线电机的多层理论分析模用该模型对一台样机进行实例计算，并与磁阻抗法和实验值进行了比较，计算结果表明该方法的正确性和有效性。     

REACTIVE POWER COMPENSATION OF A THREE-PHASE TANDEM INDUCTION GENERATOR

ABSTRACT

This paper examines the ability of capacitors connected in the supply lines to one stator to improve the power factor and efficiency of a two stator (one moveable), single squirrel-cage, three phase induction machine termed a tandem machine. An equivalent circuit model incorporating the series capacitor is presented. Theoretical modeling for a typical set of equivalent circuit parameters and optimum capacitance show the tandem induction generator's power factor transformed from lagging to leading and the efficiency improved by one to three percentage points. Results from laboratory tests on a one horse power tandem motor for two different values of capacitance are included.     

SPLIT-WINDING STARTING OF A SINGLE-PHASE INDUCTION MOTOR

Abstract

Results of investigation of starting a single-phase induction motor having a single stator winding and using normal stator and rotor punchings are presented in this paper. Theoretical and experimental studies show that the motor requires less copper for its stator winding compared to a split-phase motor and the overall starting performance is very satisfactory.     

PERFORMANCE STUDY OF A CHOPPER-CONTROLLED INDUCTION MOTOR

Abstract

In this paper, the speed of an induction motor is controlled using a chopper circuit on the rotor side. Analysis of transient, including switching power supply and changing in duty cycle of chopper, and steady-state performance of the chopper-controlled induction motor are predicted-Analysis and simulation consider the induction motor equations from the rotor side where a diode bridge is connected. Experimental results are obtained to verify predicted behaviour based on this digital simulation.     

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.     

电机启动过程信号的周期域分析

在简单介绍过程信号周期域分析方法之后,结合1台异步电动机启动、空转、关断过程信号的实际取样数据,通过周期域分析,获得了众多时、频域参量的周期域特性曲线,并分别对它们进行了必要的解释。周期域分析方法将会在过程信号分析中得到了广泛地应用。     

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。     

基于相关分析的感应电机定子故障诊断方法研究

分析了感应电机定子线圈短路故障时的振动特征及定子电流的谱特性，指出由于受电机固有不对称等因素的影响，单纯利用振动谱分析或定子电流信号频谱分析(MCSA)诊断定子线圈短路故障，不能得到准确可靠的诊断结果；提出了一种基于相关分析的感应电机定子故障诊断方法，能有效提取电机定子故障时的特征信息，利用该方法可提高故障识别的精度；实验结果证实，基于相关分析得到的谱特征可以作为感应电机定子线圈短路故障诊断的依据。     

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.     

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。