ROLE OF TORQUE ANGLE IN INVERTER-FED INDUCTION MOTOR DRIVES

ABSTRACT

It is shown from the induction motor differential equations that changes in load torque, speed reference and torque angle are accompanied by a transient change in the speed of the air-gap mmf. The time constant associated with the torque angle change is different for a voltage source and a current source inverter-fed induction motor. This aspect throws light on the instability of current source inverter-fed induction motor on open loop operation. Evidently, the solution to overcome this instability is to use the torque angle for feedback control. It is proved that torque angle feedback alone is not sufficient for stabilization of the current source inverter-fed induction motor.     

PERFORMANCE ANALYSIS OF THE REPULSION MOTOR CONTROLLED VIA ROTOR TRIAC

ABSTRACT

This paper investigates the solid state speed control of a repulsion motor using a triac in the rotor circuit. The speed control is accomplished by varying the triac firing angle. In addition, this paper investigates the harmonic contents of the rotor current, stator current and rotor voltage The waveforms of these variables were generated and then analyzed numerically for their harmonic content using a Fouries Series Subroutine. The results were validated by comparison with obtained experimental results. More over, the harmonics generated using this type of speed control are compared with those generated when the motor is controlled via a triac in the stator cicuit.     

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.     

Control Algorithm for the Inverter Fed Induction Motor Drive with DC Current Feedback Loop Based on Principles of the Vector Control

ABSTRACT

This paper brings out a control algorithm for VSI fed induction motor drives based on the converter DC link current feedback. It is shown that the speed and flux can be controlled over the wide speed and load range quite satisfactorily for simpler drives. The base commands of both the inverter voltage and frequency are proportional to the reference speed, but each of them is further modified by the signals derived from the DC current sensor. The algorithm is based on the equations well known from the vector control theory, and is aimed to obtain the constant rotor flux and proportionality between the electrical torque, the slip frequency and the active component of the stator current. In this way, the problems of slip compensation, Ri compensation and correction of U/f characteristics are solved in the same time. Analytical considerations and computer simulations of the proposed control structure are in close agreement with the experimental results measured on a prototype drive.     

Ac Line Harmonics Caused by Three-Phase Half-Controlled Converters with DC Motor Load

ABSTRACT

This paper gives a study of line harmonics generated by three-phase half controlled bridge converters feeding separately excited D.C. motor. Analytical expressions for line current are given and dominant current and voltage harmonics have been computed for a typical system. The study shows that current has predominant low order harmonics, the second harmonic being significantly large as compared to other harmonics. The line voltage, however, has significant higher order harmonic components as well Line current harmonics are dependent on motor operating speed, whereas the voltage distortion factor is nearly independent of speed. On the other hand, percent current harmonics are nearly independent of torque, but the voltage harmonics and voltage distortion factor are dependent on load torque.     

PARAMETER IDENTIFICATION OF A SEPARATELY EXCITED OC MOTOR FOR SPEED CONTROL

ABSTRACT

This paper presents the application of the least error squares (LES) parameter identification algorithm to. obtain parameters of a separately excited DC motor. The parameters of interest are; the resistance and inductance of the armature windings (Ra.Lt). the motor inertia (J), the damping constant (D), the torque and back emf constant (K) and the load torque constant (μ.). The data used are the motor input voltage, and the corresponding rotor speed. It is assumed that the trajectory of the motor speed as well as the corresponding input voltage are known and sampled at a preselected rate. Simulation results for a separately excited dc motor used in robotics are reported showing good agreement with actual parameter values.     

A Real-Time Application of Modified Inductor Coupled KY Converter Topology in Speed Control of E-Bikes

Abstract

Congested road network and traffic jam lead to vehicle idling and fuel wastage. An E-bike which is a solution to this is often available with Thumb Throttle Mechanism and single speed operation. A motor controller with multiple output voltage levels and Click Throttle Mechanism is presented in this paper which provides variable speed operation, better power utilization and is highly economical. Proposed modified KY converter utilizes the turns ratio of an On-Line Tap Changer (OLTC) to generate multiple output voltages for variable speed commutation. This possess a stable continuous conduction mode throughout its operation and reduced switching transients when compared to the existing topologies. Mutually independent control variables namely turns ratio and duty ratio, are used here for voltage conversion, which facilitates the flexible transition between multiple output voltage levels. A 15?W prototype of the proposed modified inductor coupled KY converter is realized using Arduino Uno Board.     

CLOSED LOOP PERFORMANCE OF INDUCTION MOTORS WITH CONSTANT VOLTS/HERTZ CONTROL

ABSTRACT

Characteristics of a closed loop induction motor drive, supplied from a variable frequency voltage source, and operating under constant volts/hertz control are presented. The motor linearized equations in the synchronously rotating reference frame are used to analyse the drive dynamic performance. It is shown that this performance can be greatly improved by including a properly designed speed controller in the drive structure. Thus, the decrease in stability, associated with the open loop motor operation is eliminated and the resulting drive gives satisfactory performance over the entire input frequency range. The experimental results, which confirm the validity of the motor dynamic model are also included.     

THYRISTOR CONTROLLED PULSATING FIELD RELUCTANCE MOTOR SYSTEM

ABSTRACT

Integral horsepower pulsating field reluctance motors are treated when operating in dc-supplied, fixed voltage, thyristor controlled variable speed systems. A thyristor controller with two operating modes is described. Exciting MMF differential equations are put into normalized forms, simplifying their solutions, which are given. Three parameters Q, p and x_rs concisely character= rize motor, MMF differential equations and torque. For typical speed/torque curves thyristor control angles are determined. Optimum pole- and gap dimensions are investigated on the basis of published permeance charts.     

INVESTIGATIONS ON DYNAMIC BEHAVIOR OF PERMANENT MAGNET BRUSHLESS DC MOTOR DRIVE

ABSTRACT

Permanent magnet brushless dc (PMBLDC) motors are increasingly being used in a wide range of applications such as machine tools, robotics and high precision servo applications. A comprehensive analysis which includes modeling and simulation of PMBLDC motor drive is presented in this paper. A mathematical model of the drive is developed with a view to studying the transient response of current controlled voltage source inverter (VSI) fed PMBLDC motor. The drive system consists of discrete PID(Proportional, integral plus derivative) speed controller, the reference current generator, the position sensor, an inverter and the motor. Each part of the drive system is modeled separately and then integrated to study the dynamic behavior of the drive system. The study also examines the effectiveness of the drive system during starting, load perturbation, speed reversal and dc link voltage fluctuation.     

Computer-Aided Analysis of a Converter-Fed Saturated Synchronous Motor Drive

ABSTRACT

A method of numerical simulation for evaluation of the performances of a variable speed synchronous motor drive is developed. The machine has rotor saliency with armature and damper windings. Magnetic saturation in both d and q axes are also taken into consideration. The model is focused specially for analysis of a self-controlled reluctance motor drive fed either by voltage source inverter or current commutated inverter. The computer solution permits accurate calculation of current, voltage, and torque waveforms. Sample calculations for highly saturated converter-fed reluctance motor drive are presented including comparison with practical tests.     

OPERATION OF DC MOTORS POWERED BY PHOTOVOLTAIC CONVERTERS

ABSTRACT

Utilization of solar energy (by means of photovoltaic conversion) for driving electromechanical systems in remote places is becoming nowadays economical justified. Since the output of solar cells is DC voltage, the DC motor is an obvious candidate for these systems. The performance characteristics (operation and control characteristics) of the seperate, series and shunt excitation motors powered by the photovoltaic converter was analysed. These characteristics are different from those of the conventional power supply.     

ANALYSIS OF DISCONTINUOUS CONDUCTION IN A PWM DC CHOPPER DRIVE SYSTEM

ABSTRACT

This paper is concerned with the problem of analysis of quasi-steady and transient processes in a p.w.m. d.c. chopper drive system. An analitycal approach to the performance analysis of a d.c. separately excited motor fed from a chopper and operated in the region of discontinuous conduction is presented. The system equations are solved to obtain closed form solutions for motor current and speed, for quasi-steady as well as transient conditions. The solution for quasi-steady state condition corresponding to any set of operating conditions/voltage, chopper duty factor, load torque/ and mechanical characteristics of the drive are directly obtained.

Performance analysis of the system presented in this paper can be directly extended to a more complicated systems/for example, containing RLC input or output filter/.     

基于Buck-Boost矩阵变换器的异步电机调速系统控制策略

针对以Buck-Boost矩阵变换器(BBMC)为功率变换器的异步电机调速系统,提出一种基于有限时间控制的变频调速控制方法。首先,根据异步电机的给定转速,经基于PI-IP控制的矢量控制算法获得异步电机的给定电压,并以该给定电压作为BBMC的参考输出电压。再以BBMC中电容电压与电感电流作为系统控制变量,经有限时间控制算法得到BBMC中对应功率开关的占空比。再根据该占空比对BBMC中对应功率开关实施控制,由此可在BBMC输出端获得与其参考输出一致的输出电压,从而实现异步电机实际转速对其给定转速的准确跟踪,达到对异步电机转速进行准确控制的目的。最后通过仿真和实验对上述控制方法进行了验证。     

The Minimum Input Power Conditions for Induction Motors Fed from Variable Frequency Sources

ABSTRACT

A simplified analytical method, based on the equivalent circuit of an induction motor, is presented for computing the frequency and voltage corresponding to the minimum input power. This optimum operating condition is determined for a specified torque and within a specified speed range. It is shown that the optimal per unit slip lies between the limits of zero and r₂/x₂     

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.     

CONTROL OF SINGLE PHASE INDUCTION MOTOR USING FORCED-COMMUTATED ELECTRONIC SWITCHES

ABSTRACT

Single phase induction motors require assistant methods for starting, speed-control and reversing direction of rotation. The available methods suffer from many drawbacks. Most of these drawbacks are due to use of mechanical switches in addition to other expensive electrical equipment. This paper suggests a nonconventional versatile method which realizes all the motor requirements. The method uses two forced-commutated electronic switches to feed a single-phase motor which has two symmetrical stator windings. By this circuit, the motor could produce a high starting torque. Also the speed could be controlled and the direction could be reversed. A state space mathematical model has been developed for the motor and its solid state feeding converter. With the aid of the model, the system has been simulated by a developed computer program. Transient starting characteristics have been computed. Also, steady state speed control characteristics have been obtained for different control strategies. The performance of the motor has been compared with other conventional control methods, and with a method which uses naturally commutated electronic switches.     

Implementation of a single-phase matrix converter induction motor drive

This paper presents an implementation of a single-phase matrix converter for a variable speed single-phase induction motor. The paper analyzes the characteristics of a single-phase ac–ac converter drive with particular emphasis on the harmonic content, input voltage utilization and variable speed performance of the motor. Both square and sinusoidal wave modulation signals in PWM generation have been used to demonstrate the effect of the modulating signal on the input voltage utilization and output harmonic content. Simulation and experimental results for an R–L and induction motor loads are presented. Promising results illustrate that a good performance of a single-phase induction motor fed by a matrix converter is achievable.     

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.     

NEUTRAL-TO-GROUND VOLTAGE MINIMIZATION IN A PWM-RECTIFIER / INVERTER CONFIGURATION

ABSTRACT

High frequency common mode voltage produced by power converters are a major cause of conducted EMI, creating motor ground currents, bearing currents and other harmful by-products. In this paper a control algorithm for an induction motor fed by a fully controlled rectifier and inverter is developed to reduce the common mode neutral-to-ground voltage of the induction motor. A bearing current model is used to evaluate the effects on the bearing currents of the double bridge modulation scheme when the new algorithm and conventional algorithms are used. Simulation results are shown to demonstrate the benefits of the new PWM approach.