COMPUTER CONTROL OF THYRISTORIZED INDUCTION MOTORS AND ON-LINE PERFORMANCE PREDICTIONS

ABSTRACT

This paper describes a method of modelling the dynamic behaviour of thyristor controlled induction motors. Real time operational verification of the model is achieved by interfacing the drive system to a computer. The steady state torque produced by the motor is described as a function of firing angle, extinction angle and speed. The model concentrates on the open loop transfer functions of induction machines for small perturbations in motor speed and firing angles. The non-linear characteristics of the open loop transfer function has been discussed. The solutions presented here can lead to a comprehensive closed loop analysis for the dynamic behaviour of induction motors in industrial applications.     

EFFECTS OF INDUCTION MOTOR LOAD ON DYNAMIC STABILITY OF POWER SYSTEMS

Abstract

A study of the effects of induction motor load on the dynamic stability of power systems is presented in this paper. The power system is modelled as a multivariable system with load dynamics considered in the feedback path. The induction motor is represented by a transfer function matrix relating bus voltage magnitude and frequency to the active power and reactive power of the motor

Multivariable Nyquist criterion and eigenvalue analysis are used to investigate the effects of induction motor dynamics on system stability     

PERFORMANCE OF ROTARY-LINEAR INDUCTION MOTOR WITH ROTATING-TRAVELING FIELD

Abstract

A rotary-linear induction motor whose stator creates a magnetic field traveling helically is presented. A theory of such a motor is derived taking into account a finite excitation length of the stator. Results obtained from the calculations are verified experimentally.     

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.     

SINGLE-PHASE MOTOR INDUCTION-RUN PERFORMANCE

ABSTRACT

Based on the rotating-field theory and the ‘exact’ equivalent circuit of a single-phase induction motor operating on its main winding only, accurate solutions are derived for the salient features of its torque to speed performance at pull-out and zero torque, to enable the torque-speed plot to be readily compiled with sufficient accuracy for preliminary-design purposes. The torque, current, power factor and efficiency at any speed are also derived for use in the final-design stage, again on the assumption that the airgap mmf is sinusoidally distributed. However, in order to be strictly applicable to many modern designs, the analysis is extended to cover in a simple manner the general case of significant space-harmonic mmfs being present in the airgap.     

OPTIMIZATION OF AN ELECTRONICALLY CONTROLLED CAPACITOR FOR A SINGLE-PHASE INDUCTION MOTOR

ABSTRACT

In this paper the performance of a single-phase induction motor with an electronically controlled capacitor is examined. The capacitor in series with the auxiliary winding is controlled with an electronic circuit and different optimization criteria are applied in order to determine the optimum capacitance of subsequent performance of the motor.     

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.     

IMPROVED PERFORMANCE OF HIGH-SPEED SINGLE-SIDED LINEAR INDUCTION MOTORS: A THEORETICAL STUDY

ABSTRACT

It is shown that a high-speed - 80 to 120 m/s - single-sided linear induction motor (SLIM) can perform almost as well as a double-sided one, if the secondary of the SLIM is made up of an aluminum plate mounted on a back-iron consisting of two or three longitudinal ‘solid’ laminations. This feature retains most of the advantages of a SLIM such as compatibility with guideway and low costs of material, mounting and maintenance. Thus, a SLIM, with solid laminations for back-iron, is analyzed including the consequences of the machine topology and physical phenomena. A numerical example is given to compare the results with those for the largest existing double-sided motor.     

FLUX DISTRIBUTION AND REACTANCE IN ENCLOSED SLOT SOLID ROTOR INDUCTION MOTOR

ABSTRACT

In this paper flux distribution by finite element method in the solid rotor with enclosed slot induction motor compared with the flux distribution in the laminate core rotor with enclosed slot is examined.

This paper also presents a method of deriving the reactance from the magnetic energy stored at the portion of the rotor surface. The method of calculating the reactance of the slot tip of an induction motor with enclosed slots is examined. The starting performance calculation of this motor are also described.

Explanation is made here in the order as follows: Equivalent circuit of enclosed slot solid rotor induction motor, Flux distribution in the solid rotor with enclosed slots, Method of deriving the reactance from stored and accumulated magnetic energy, Calculation of the flux distribution, Examples of calculations on the reactance of the slot tip, Results of calculation and measurement on characteristics of the tested motor.

The method of deriving the reactance from the magnetic energy stored in the surface region of the core is considered to be utilizable widely in the technology of magnetic circuits involving non-linear magnetic characteristics     

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.     

直线异步电机的可靠性试验

直线异步电机的可靠性对用户和制造商均极为重要.分析了直线异步电机的故障树,提出了电机的失效判据和主要的可靠性指标.现场使用的电机基本运行在偶然失效阶段,因而其失效率近似为一常数.在恒定失效率的假设下,推荐采用定时或定数截尾试验方案在现场进行电机的可靠性试验.     

Efficient dynamic models for induction machines

A computationally efficient reluctance mesh model suitable for simulating the dynamic performance of practical induction motors is presented. The calculation time is minimized by direct computation of rate of change of flux, avoiding unnecessary evaluation of time and rotor position dependent inductances. The magnetic, electrical and dynamic models of the machine are coupled so that the simulation determines both steady state and transient behaviour including the effects of saturation and high order torque harmonics due to the rotor and stator teeth. The algorithm is developed from rigorous field theory. This is combined with and simplified by, practical experience, resulting in a procedure that can efficiently simulate 3D machines within an iterative design environment without requiring extensive computational resources. Full details of the implementation are presented along with simulations and experimental characterization of a practical induction motor which are found to be in ‘excellent’ agreement. Copyright © 1999 John Wiley & Sons, Ltd.     

COMMUTATION CONTROL DURING SPEED REVERSAL OF A CURRENT-FED ASYNCHRONOUS MACHINE

ABSTRACT

This article examines the process of interchanging two phases in a converter in order to reverse the direction of rotation of a motor. The risk of a commutation failure, due to a significant decrease in the commutation capacitor voltage after the inversion of the two phases is presented. In order to overcome these faults, a solution is proposed, consisting of a controlled delay of main thyristor energizing. The advantages of this delay are demonstrated on an experimental assembly.     

A COMPANION CIRCUIT MODEL OF INDUCTION MOTORS

ABSTRACT

The theory of a companion circuit model of the induction motor is presented. The model comprises an independent current source in parallel with a constant resistance. Accuracy of problem solutions is the same as that obtained from conventional models, but the time of solution is much shorter. This stems from the combined consideration given to the problem formulation and its solution. A companion circuit model can include extra sets of machine coils such as those needed to represent deep-bar effects. Conventional motor models are adequate for single-machine, transient studies. It is for multi-machine studies that the companion circuit concept provides advantages for formulation and solution.     

OPTIMAL TRACKING OF THE DYNAMIC PERFORMANCE OF AN INDUCTION MACHINE

ABSTRACT

This paper describes the application of optimal tracking methods to identify the parameters of an induction motor. The data required can be obtained by conducting an acceleration test on an unloaded motor. The effect of the saturation of the leakage flux paths as well as the skin effect in rotor bars have been considered. The parameters of the motor thus identified can then be used to obtain any required characteristics of the motor.     

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.     

TEST PROCEDURE FOR VERY HIGH SPEED SPINDLE MOTORS

Abstract

In the last ten years, the new power electronic devices and the new control techniques have allowed to open new application fields for adjustable speed/torque electrical drives. Although the traditional dc drives keep still the market supremacy, the new ac drives have performance really attractive and some additional benefits due to the machine structure and to the maintenance costs. Usually, ac drives use induction or brushless motors and the power amplifiers are driven by variable voltage/frequency in order to obtain variable speed. The authors deal with induction motors fed by non conventional supplies at very high frequency. In order to evaluate the total motor losses and the single items, a test bench with a synchronous machine capable to work up to 2 kHz with sinusoidal output voltage has been set up. As a consequence, an induction motor equivalent circuit with parameters depending on the frequency has been proposed. Today, the empirical procedure is that to use for high frequency applications shelf motors derated of a factor 10 to 20 % in order to keep into account the extra harmonic losses. On the other hand, the authors propose to design ‘ad hoc’ the motors for six-steps continuous operation in order to get about the same efficiency of standard motors. The new proposed motor equivalent circuit together with the test procedure seem to be a practical tool in order to aid the new motor design.     

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     

EFFECTS OF LOAD INDUCTANCE ON THE RIPPLES OF MULTIPHASE CHOPPER CONTROLLED DC MOTOR DRIVE

ABSTRACT

This paper derives simple expressions to calculate the ripple currents and voltage of a multiphase chopper control DC motor drive. A typical example is considered and the results of the simple equations are compared with those obtained from the solutions of the differential equations without approximations. The effects of the load current ripple and the multiphase operation of choppers on the ripple voltage and current of the ‘LC’ input filter are also evaluated.