Handbook of Asynchronous Machines with Variable Speed E-Book

Hubert Razik

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 423

Veröffentlichungsjahr: 2013

Beschreibung

This handbook deals with the asynchronous machine in its close environment. It was born from a reflection on this electromagnetic converter whose integration in industrial environments takes a wide part. Previously this type of motor operated at fixed speed, from now on it has been integrated more and more in processes at variable speed. For this reason it seemed useful, or necessary, to write a handbook on the various aspects from the motor in itself, via the control and while finishing by the diagnosis aspect. Indeed, an asynchronous motor is used nowadays in industry where variation speed and reliability are necessary. We must know permanently for the sensitive systems, the state of process and to inform the operator of the appearance of any anomaly and its severity.

Leseprobe

Table of Contents

Foreword

Introduction

Chapter 1. Sensors and Electrical Measurements

1.1. Optical encoder

1.2. The velocity measurement

1.3. The resolver

1.4. The isolated measurement

1.5. The numerical aspect

1.6. The analog to digital converter

1.7. The digital-to-analog converter

1.8. The digital output

1.9. The arithmetic logic unit

1.10. Real time or abuse language

1.11. Programming

Chapter 2. Analog, Numerical Control

2.1. Structure of a regulator

2.2. Stability of a system

2.3. Precision of systems

2.4. Correction of systems

2.5. Nonlinear control

2.6. Practical method of identification and control

2.7. The digital correctors

2.8. Classical controllers

2.9. Disadvantages of digital controller

Chapter 3. Models of Asynchronous Machines

3.1. The induction motor

3.2. The squirrel cage induction motor

3.3. The static and dynamic behavior

3.4. Winding and induced harmonics

3.5. Squirrel cage

3.6. Variation in air-gap permeance

3.7. Noise and vibrations

3.8. Influence of rotor frequency

3.9. Thermal behavior

Chapter 4. Speed Variation

4.1. Cases of multiphase machines

4.2. Control of asynchronous motors

4.3. Identification of parameter aspects

4.4. Voltage inverter converters

4.5. Rectifiers based on the PWM

Chapter 5. Tools of Fuzzy Logic

5.1. Preamble

5.2. Introduction

5.3. Fuzzy logic

5.4. Fuzzy logic controller

5.5. Fuzzy and adaptive PI

5.6. Conclusion

Chapter 6. Diagnostics and Signals Pointing to a Change

6.1. Signals and measurements

6.2. Defects

6.3. Analysis of signals

6.4. Some considerations regarding broken bar defects

6.5. Evaluation of the severity of broken bars

Exercise No. 1: Fuzzy Logic

1.1. Adaptive k and ki coefficients in function of the error

1.2. Adaptive k and ki coefficients in function of the error and its derivative

1.3. Answers

Exercise No. 2: The Stator Defect

2.1. Equations of the induction motor under stator defect

2.2. Torque ripple due to a stator defect

2.3. Fault current estimation

2.4. Schematic model of three-phase induction motor under a stator defect

2.5. Answers

Exercise No. 3: The Control of Five-Phase Induction Motors

3.1. The five-phase system

3.2. Distribution of active currents

3.3. A model for control

3.4. Answers

Exercise No. 4: The Control of Serial Connected Induction Motors

4.1. Study about the serial connection of two five-phase induction motors

4.2. Study on the serial connection of several seven-phase induction motors

4.3. Study on the serial connection of multi-phase induction motors

4.4. Answers

Exercise No. 5: Fault Detection of a Three-Phase Voltage Inverter Converter

5.1. Aconducting fault

5.2. Fault detector

5.3. Monitoring of the DC component

5.4. Answers

Appendix. Some Mathematical Expressions

A.1. Laplace transforms

A.2. Z transforms

A.3. W transforms

A.4. Common expressions

A.5. Trigonometric identities

A.6. Mathematical series

A.7. Greek numbers

Bibliography

Index

First published 2011 in Great Britain and the United States by ISTE Ltd and John Wiley & Sons, Inc.

Adapted and updated from La machine asynchrone à vitesse variable 1&2: capteurs, modèles, contrôle et diagnostic published 2006 in France by Hermes Science/Lavoisier © LAVOISIER 2006

Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act 1988, this publication may only be reproduced, stored or transmitted, in any form or by any means, with the prior permission in writing of the publishers, or in the case of reprographic reproduction in accordance with the terms and licenses issued by the CLA. Enquiries concerning reproduction outside these terms should be sent to the publishers at the undermentioned address:

ISTE Ltd27-37 St George’s RoadLondon SW19 4EUUK

John Wiley & Sons, Inc.111 River StreetHoboken, NJ 07030USA

www.iste.co.uk

www.wiley.com

© ISTE Ltd 2011

The rights of Hubert Razik to be identified as the author of this work have been asserted by him in accordance with the Copyright, Designs and Patents Act 1988.

Library of Congress Cataloging-in-Publication Data

Razik, Hubert.

Handbook of asynchronous machines with variable speed / Hubert Razik.

p. cm.

Includes bibliographical references and index.

ISBN 978-1-84821-225-1

1. Electric machinery, Induction--Automatic control. 2. Electric motors, Induction--Automatic control. 3. Electric driving, Variable speed. I. Title.

TK2731.R37 2011

621.31’36--dc22

2010048625

British Library Cataloguing-in-Publication Data

A CIP record for this book is available from the British Library

ISBN 978-1-84821-225-1

Foreword

The asynchronous machine, also known as the induction machine, has been an industry workhorse for more than 120 years. The first rotating machine to work using alternating current, its advent started a new chapter in the evolution of our society, with the propagation of long-distance electrical lines ensuring a large distribution of electrical energy and a systematic replacement of steam-powered machines with electrical ones. This expansion still continues today, as much in industrial applications and transport as home automation. The induction machine is a part of our everyday lives in the broadest sense: it is present in all Western households and emerging and developing countries strongly depend on its use.

Naturally, since its first appearance, the induction motor has undergone revolutions and changes through the development of techniques and progress in the field of magnetic or dielectric materials. This can easily be seen from the size of the machines, with a power-to-mass ratio that has considerably evolved and can operate at variable speeds, which makes it a broad-spectrum actuator. The intrinsic performances of this machine have considerably progressed, first through a more optimized construction of its structure and by the use of better quality materials, but mostly from the set-up of an adapted electronic environment allowing the optimized management of energy processing.

To this end, this book by Professor Hubert Razik provides an eloquent and original testimonial by discussing in an educational and rational way all the constituent elements of a variable speed drive at the base of the asynchronous machine. In this way we can easily navigate between methods and tools, principles and rules in order to cover all the angles of modern control of this machine, by making the link between signal processing, control and diagnostics.

This book is split into six chapters and accompanied by a bibliography consisting of the greatest contributions to the field.

Chapter 1 covers sensors and electrical measurements and brings to light, in a concise way, the notions of coding and restitution of information that can be read by a controller.

Chapter 2 clarifies the fundamental elements for the control of the systems, through a review of the representation and synthesis of corrector tools in the context of electric motor control (identification, nonlinear control, stability, data quantization, etc.).

Chapter 3 covers the modeling of induction motors, with a gradual evolution from simple models valid in nominal cases, up to taking into account very unusual phenomena such as magnetic saturation, rotor eccentricity or thermal incidence. It contains a very explicit and relevant contribution.

Chapter 4, the longest of all, splits speed variation into its different aspects. It discusses scalar, then vector control, then passes through direct torque control and controls without mechanical sensors. This part is subject to several declinations, be it over the phases of the motor (five- or six-phase motor) or even over the number of inverter output levels (three level, four or multi-level). This chapter is even more valuable since it is based on the real know-how of the author. It is the result of long and meticulous practice, searching for better solutions.

Chapter 5 covers fuzzy logic, by simply setting down the meets and bounds of this approach and its applications for control of the asynchronous motor. The basis is carefully shown, allowing quick and relevant applications for the given potentials.

The final chapter — Chapter 6 — covers the delicate problem of diagnostics of electric motors, which is currently the subject of ever more numerous and open research. Professor Razik’s contribution to the field is very well developed. He has compiled an inventory of different problems and proposed methods of detecting and identifying defects. Ultimately, machine monitoring is proposed via the use of wireless communication.

The author’s educational background is present throughout this book. For completion, the book proposes a series of corrected exercises that allow the assimilation of the concepts needed for this discipline.

The operation and diagnostics of electric motors, such as induction motors, remains a very complex discipline since it brings into play conversion and processing phenomena of electrical energy with a distinct nonlinear character. This is an example of an application that joins significant know-how and we thank Professor Razik for this accessible work, demystifying the laws of control and diagnostics of these devices.

This book will be useful for postgraduate students, engineering students, their tutors and other young researchers starting a career in this field where much progress is awaited. The interconnection of the notions covered make this a complete book for the field of electric motors.

Professor Maurice FADEL ENSEEIHT Deputy Director of LAPLACE

Introduction

This book is aimed as much at students and postgraduates, whether working in research or not, as it is for tutors and engineers.

It offers students knowledge that goes from the basics to a much more advanced level; the broad spectrum offered to readers allows easy comprehension of more specialized books. Exercises are included at the end of the book.

Engineers will be able to find elements corresponding to their needs, whether academic or providing the in-depth knowledge that will give them the tools for broader thinking.

This book covers the asynchronous machine in its immediate environment. It started out as a reflection on the electromagnetic converter, whose integration in industrial environments is taking on an increasingly important role. Historically this motor was used in a chain of a fixed speed process. Now it is increasingly being integrated in variable speed processes. It is for this reason it seemed useful, if not necessary, to write a book covering the different aspects from the motor itself, passing through control and finishing with the diagnostic aspect. In fact, asynchronous motors are today in an industry where variation of speed and reliability are required. For sensitive systems, we should always know the state of the conversion chain and inform the operator of the appearance of any anomaly and its severity.

All these approaches are described in a rigorous manner and numerous references will allow readers to further develop their comprehension and knowledge.

I would like to thank my wife and my daughters for their loving support throughout this endeavour.

Chapter 1

Sensors and Electrical Measurements

Measurement is an obligatory phase that we cannot avoid. In fact, in all electromagnetic processes whether at a variable or constant speed instructed measurements are carried out. These measurements are compared to those taken to correct the process so that they conform to the desired values. This phase is used as a control and in some cases is incorporated into regulations. Such a system can generally be split into four parts, as we see in Figure 1.1, which are:

(1) instruction(s) and protection: these different parts allow us to take into account the needs and constraints;

(2) control and regulation(s): this is dedicated to control loop that can consist of several interleaved loops;

(3) electric supply: this is an interface allowing application of the desired voltages to the motor in alternating current;

(4) electric motor: this converts electrical energy into mechanical energy.

Between these parts, connections are necessary, either to transmit information (instructions between parts) or to transmit energy from a source of power towards the electric motor. For this, analog lines such as coaxial or fiber optics are used for power. For instruction(s) and regulation(s), digital connections are preferred. It will be necessary to represent the numbers in digital form, which will lead to a quantization that will be represented in binary form. The choice is not without consequence, since this noise of quantization will alter the performance of the system (closed loop process). Nevertheless, we can reasonably say that a representation between 12 and 16 bits is acceptable for the majority of microcontrollers for regulation.

Figure 1.1.Flow diagram representing the process with regulation

Let us approach the measurement aspect of the angular position of a mechanical shaft, then its rotation speed. For this, two categories of coders exist: one is optical and the other is electromagnetic.

1.1. Optical encoder

Different types of optical coders exist. Certain ones have many advantages and others fewer, along with the inherent constraints of the choice of technology used. For this reason, we will first cover the measurement of the absolute position and second the measurement of the relative position of the mechanical shaft.

1.1.1. Technical aspect

What is an optical encoder?

An optical encoder is a system that allows us to provide logic level transitions 1 and 0 depending on the mechanical rotation. It consists of a disc with cuts similar to a multitude of lines that allow light to pass though. In this way a beam of light will excite a receiver, which will provide either level 1, or level 0 transitions after transformation of the collected signals. Figure 1.2 is a synoptic diagram of an optical encoder where we can discern the disc itself with it axis of revolution, light emitter, receiver and space letting the beam of light pass through.