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No. a K S4DcESIGaN SrERVlICiESS OlF e 24626_fm_ptg01_hr_i-vi.indd 1 12/6/11 6:01 PM Title: Motor Control Fundamentals, Server: Short / Normal Publishing Services Motor Control Fundamentals © 2013 Delmar, Cengage Learning Steve Senty ALL RIGHTS RESERVED. No part of this work covered by the copyright herein may be reproduced, transmitted, stored, or used in any form or by any means Vice President, Editorial: Dave Garza graphic, electronic, or mechanical, including but not limited to photocopying, Director of Learning Solutions: Sandy Clark recording, scanning, digitizing, taping, Web distribution, information networks, Acquisitions Editor: Stacy Masucci or information storage and retrieval systems, except as permitted under Managing Editor: Larry Main Section 107 or 108 of the 1976 United States Copyright Act, without the prior written permission of the publisher. 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No. b K S4DcESIGaN SrERVlICiESS OlF e 24626_fm_ptg01_hr_i-vi.indd 2 12/6/11 6:01 PM Title: Motor Control Fundamentals, Server: Short / Normal Publishing Services Table of Contents preface v Chapter 1 Electromagnetic Induction Chapter 8 Overload Units 111 Theory 1 Thermal Overload Units 112 The Principle of Electromagnetism 2 The Principle of Electromagnetic Induction 3 Chapter 9 Magnetic Motor Starters 119 Relationship Between Electromagnetic Definition 120 Induction and Electromagnetism 3 Induction May Be Either Chapter 10 Motor Starter Circuits 127 Mutual Induction, or Motor Circuit Conductor Protection 128 Self-Induction 4 Magnetic Motor Starter Circuit 128 Chapter 2 Induction Motor Overview 11 Chapter 11 Motor Control Circuit Ladder The Parts of an Induction Motor 12 Diagram Documentation 135 What Is an Induction Motor? 16 Reference Documentation 136 Chapter 3 Three-Phase Motor Theory 25 Chapter 12 Two-Wire Motor Control 145 Law of Charges 26 Two-Wire Motor Control Circuits 146 Electromagnets in Induction Motors 27 Synchronous Speed 33 Chapter 13 Three-Wire Motor Control 151 Chapter 4 Single-Phase Induction Motors 39 Three-Wire Motor Control Circuits 152 Single-Phase Alternating Current (AC) Motors 40 Single-Phase Induction Motor Classifications 45 Chapter 14 Control Circuits 159 Two-Wire Control Circuits 160 Chapter 5 Induction Motor Electrical Three-Wire Control Circuits 160 Connections 53 Motor Connections 54 Chapter 15 Variable-Frequency Drive Principles 179 Chapter 6 Motor Nameplates 75 Advanced Motor Protection Features 180 Motor Nameplate Information 76 Chapter 16 Commissioning a VFD 189 Chapter 7 Magnetic Relays and Contactors 91 Index 195 Parts of a Relay 92 Magnetic Contactors 100 iii # 106957 Cust: Senty Au:Cengage Pg. No. iii K S4DcESIGaN SrERVlICiESS OlF e 24626_fm_ptg01_hr_i-vi.indd 3 12/6/11 6:01 PM Title: Motor Control Fundamentals, Server: Short / Normal Publishing Services This page intentionally left blank Preface The word “motors,” as stated in the title, represents of content available on motors, and it is impossible a diverse and complicated topic of study. There for a single textbook to cover all of it. Trying to are many different types of motors, and several cover too much content in a short period of time different methods of converting electrical energy can overwhelm learners, and leave them confused into rotating mechanical energy via electromagne- and unable to assimilate even the most important tism. The focus of this book is to understand basic basic content. Like the math learner who has never single-phase and three-phase induction motor understood the purpose of the parentheses in an theory and operation, common motor control algebra problem, not understanding the most ba- circuit schemes, reading, interpreting, and docu- sic concepts of any subject will lead to problems menting motor control circuit diagrams, and pro- when more advanced material is encountered. As viding practice circuits for connecting the actual instructors we sometimes forget that some of the motor control circuit components from ladder content we want to cover is very advanced, and diagrams. The focus will be limited to single- and we try to teach someone new to the electrical in- three-phase induction motors because they consti- dustry in a semester that which has taken us years tute the vast majority of motors the construction to master. electrician will encounter in the field. In the article “Minimizing AC Induction Motor COMMENTS Slip” in the trade magazine Electrical Construction and Maintenance (EC & M), dated April 1, 2004, Electric Motor Standards Mauri Peltola of ABB Drives and Motors estimates that more than 90% of all motors used in worldwide The electric motor standards that will be referenced industry are AC induction motors. If that number in this study are the standards most applicable to is adjusted to compensate for the specialized motor the construction electrician: the National Electri- types used in specific industries, it becomes ap- cal Manufacturers Association (NEMA), and the parent that construction electricians will encoun- International Electrotechnical Commission (IEC). ter an even higher percentage of induction motors In general, the NEMA standard was adopted by in their everyday work. Very few construction elec- North America, and most of the rest of the world tricians will ever encounter a wound-rotor motor, adopted the IEC standard. NEMA standard MG-1 and because this type of motor is so rare, their em- (Motors and Generators 1) sets the standard for the ployers will understand if they require help dealing construction and manufacture of AC and DC mo- with it. Every employer, however, is going to expect tors and generators, and will be the main standard employee competence in the induction motors that referenced. IEC standard 60034-1 pertains to all constitute such a large part of their work. rotating electrical machines and will be referenced The focus of this book also is confined to only for comparison with the NEMA standard. Both the most basic content necessary for the beginning NEMA and IEC motors and motor control compo- learner to understand induction motors and motor nents are common in the electrical industry today, control, and build a strong knowledge base to build so it is important to have knowledge of both stan- on in the field. There is a seemingly endless amount dards, and to understand their interchangeability. v # 106957 Cust: Senty Au:Cengage Pg. No. v K S4DcESIGaN SrERVlICiESS OlF e 24626_fm_ptg01_hr_i-vi.indd 5 12/6/11 6:01 PM Title: Motor Control Fundamentals, Server: Short / Normal Publishing Services vi prefaCe SUPPLEMENTS from production floors to new construction. Specializing in motors and motor controls, he The Motor Control Fundamentals Lab Manual taught in the Construction Electrician Programs at contains 16 lab exercises on various topics related Anoka Technical College and St. Paul College for to motor control, with some of the labs correlat- 15 years. Before that he also taught Electrical Ap- ing to specific chapters. The labs state the purpose prenticeship classes, and Journeyman Extension of the exercise, list equipment needed, provide Classes for the IBEW L.U. #110 Joint Apprentice- step-by-step instructions, and contain review ship and Training Committee. Steve Senty main- questions for reinforcement at the end of the labs. tains his membership in the IBEW, holds a 2 year ISBN: 0-8400-2463-0 Technical College Electrical Diploma, a B.A. in An Instructor Companion Website is available business, and a Class “A” Master electrical license. for this text. An Instructor Guide contains answers to the review questions at the end of each chap- ACKNOWLEDGMENTS ter, as well as answers to the Lab Manual review questions. Chapter presentations in PowerPoint The author and publisher would like to express are provided for each chapter, as well as additional thanks to those reviewers who provided insightful test banks for each chapter. An image library con- feedback throughout the development of this text: taining low resolution figure files is posted as well. ISBN: 0840024649 Mike Melaney, Moraine Park Technical College, West Bend, WI ABOUT THE AUTHOR Marvin Moak, Hinds Community College, Raymond, MS Steve Senty worked as a commercial and industrial electrician in IBEW L.U. #110 for 18 years before Don Pelster, Nashville State Community leaving the trade to teach full-time. His experience College, Nashville, TN in the trade included many areas of the industry, # 106957 Cust: Senty Au:Cengage Pg. No. vi K S4DcESIGaN SrERVlICiESS OlF e 24626_fm_ptg01_hr_i-vi.indd 6 12/6/11 6:01 PM Title: Motor Control Fundamentals, Server: Short / Normal Publishing Services chapter 1 Electromagnetic Induction Theory PurPosE to familiarize the learner with electromagnetic induction theory, electromagnetism theory, and how the two phenomena function in alternat- ing current (ac) circuits. objEcTIvEs after studying this chapter on electromagnetic • explain self-induction induction and electromagnetism theory, the • explain a counter-electromotive force learner will be able to: (ceMF) • explain electromagnetism • explain how inductors oppose a change in • explain electromagnetic induction current, and cause a phase shift between • explain the volts-per-turn principle voltage and current • explain mutual induction 1 # 106957 Cust: Senty Au:Cengage Pg. No. 1 K S4DcESIGaN SrERVlICiESS OlF e 24626_ch01_ptg01_hr_001-010.indd 1 11/17/11 1:42 PM Title: Motor Control Fundamentals, Server: Short / Normal Publishing Services 2 chapter 1 electromagnetic Induction theory THE PrINcIPLE oF individual turn of wire in the coil that is propor- ELEcTroMAGNETIsM tional to the amount of current flow. Because the current flows through each wire turn of the coil in Electromagnetism and electromagnetic induction the same direction, the magnetic polarity of each are important electrical principles for electricians individual wire turn will be the same, and all of the to understand, because many electrical compo- magnetic fields from the individual turns of wire nents operate on these principles. These electrical will add together to equal their total sum. components include transformers, generators, and induction motors, among other devices; but the Type of core Material. This factor requires some focus here is on the induction motor. The principle additional explanation. In this instance, the prop- of electromagnetism states that when an electri- erty in which we are most interested is perme- cal current flows through an electrical conduc- ability. Permeability is the measure of how easily tor, a magnetic field will be created around that a material may become magnetized, and it deter- conductor. mines how many lines of magnetic flux the ma- terial can carry per a given cross-sectional area, Determining Electromagnetic strength which is flux density. Air has a permeability of one (1), which is poor; this means that it is not eas- Three properties determine the strength of any ily magnetized and it cannot carry many magnetic electromagnet. These are: lines of flux per a given cross-sectional area. Any 1. Intensity of current flow material containing iron, however, has a perme- 2. Number of wire turns in the coil ability greater than one. Soft iron has a high 3. Type of core material. permeability, which means that it is easily magne- tized, and can carry many more magnetic lines of Intensity of current Flow. The strength of the flux per a given cross-sectional area. magnetic field created by an electromagnet is in part determined by the amount of current flow Ampere-Turns Principle in the inductor coil. With the other two factors held constant, a small current will produce a small Normally when talking about an electromagnet, magnetic field with few magnetic lines of flux, and “ampere-turns” is a term commonly used to explain a large current will produce a large magnetic field that the strength of the electromagnetic field is with many magnetic lines of flux. The magnetic determined by both the number of wire turns in polarity of the electromagnetic field is determined the coil and the intensity of current flow through by the direction of current flow through the coil; if the coil, as indicated previously. A more practi- the electrical current through the conductor is re- cal method for the technician to use when think- versed, the polarity of the magnetic field surround- ing about the strength of the electromagnetic field ing the conductor also will reverse. As the current of an electromagnet is the intensity of the current intensity and the direction of current flow through flow through the coil, because it is the only fac- the inductor coil change, as is true in an alternat- tor that can be controlled in the field. The type of ing current (AC) circuit, the magnetic field created core material used in the inductors electricians by the current flow will change correspondingly. will encounter will always be iron, because of its superior permeability; and the number of turns of Number of Wire Turns in the coil. All of the wire in an inductor coil is determined at the time small magnetic fields created around each turn of manufacture and cannot be changed in the field. of wire in the coil will add up to become a larger Of the three factors that can affect the strength of the magnetic field for the whole coil. When the elec- electromagnet in the field, the only value that can be trical current flows through the inductor coil, the controlled is the intensity of current flow, which is current will create a magnetic field around each determined by the voltage applied to the coil. # 106957 Cust: Senty Au:Cengage Pg. No. 2 K S4DcESIGaN SrERVlICiESS OlF e 24626_ch01_ptg01_hr_001-010.indd 2 11/17/11 1:42 PM Title: Motor Control Fundamentals, Server: Short / Normal Publishing Services