ELECTRICITY This page intentionally left blank ELECTRICITY DEVICES, CIRCUITS, AND MATERIALS NINTH EDITION THOMAS KUBALA Australia • Brazil • Japan • Korea • Mexico • Singapore • Spain • United Kingdom • United States Electricity 2: Devices, Circuits, and Materials, Ninth Edition Thomas Kubala Vice President, Career and Professional Editorial: Dave Garza Director of Learning Solutions: Sandy Clark Senior Acquisitions Editor: John Fedor Managing Editor: Larry Main Senior Product Manager: Sharon Chambliss Senior Editorial Assistant: Dawn Daugherty Vice President, Career and Professional Marketing: Jennifer McAvey Executive Marketing Manager: Deborah S Yarnell Senior Marketing Manager: Jimmy Stephens © 2009 Delmar, Cengage Learning 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 graphic, electronic, or mechanical, including but not limited to photocopying, recording, scanning, digitizing, taping, Web distribution, information networks, or information storage and retrieval systems, except as permitted under Section 107 or 108 of the 1976 United States Copyright Act, without the prior written permission of the publisher For product information and technology assistance, contact us at Professional & Career Group Customer Support, 1-800-648-7450 For permission to use material from this text or product, submit all requests online at cengage.com/permissions Further permissions questions can be e-mailed to permissionrequest@cengage.com Library of Congress Control Number: 2008925008 Marketing Specialist: Mark Pierro Production Director: Wendy Troeger Production Manager: Stacy Masucci ISBN-13: 978-1-4354-0069-6 ISBN-10: 1-4354-0069-0 Content Project Manager: Cheri Plasse Art Director: Benj Gleeksman Technology Project Manager: Christopher Catalina Production Technology Analyst: Thomas Stover Delmar Maxwell Drive Clifton Park, NY 12065-2919 USA Cengage Learning products are represented in Canada by Nelson Education, Ltd For your lifelong learning solutions, visit delmar.cengage.com Visit our corporate website at cengage.com Notice to the Reader Publisher does not warrant or guarantee any of the products described herein or perform any independent analysis in connection with any of the product information contained herein Publisher does not assume, and expressly disclaims, any obligation to obtain and include information other than that provided to it by the manufacturer The reader is expressly warned to consider and adopt all safety precautions that might be indicated by the activities described herein and to avoid all potential hazards By following the instructions contained herein, the reader willingly assumes all risks in connection with such instructions The publisher makes no representations or warranties of any kind, including but not limited to, the warranties of fitness for particular purpose or merchantability, nor are any such representations implied with respect to the material set forth herein, and the publisher takes no responsibility with respect to such material The publisher shall not be liable for any special, consequential, or exemplary damages resulting, in whole or part, from the readers’ use of, or reliance upon, this material Printed in the United States of America XX 11 10 09 08 CONTENTS PREFACE / vii ALTERNATING-CURRENT PRINCIPLES / INDUCTANCE AND INDUCTIVE REACTANCE / 11 CAPACITANCE AND CAPACITIVE REACTANCE / 19 SERIES CIRCUIT: RESISTANCE AND INDUCTANCE / 29 SERIES CIRCUIT: RESISTANCE AND CAPACITANCE / 37 SERIES CIRCUIT: RESISTANCE, INDUCTANCE, AND CAPACITANCE / 45 AC PARALLEL CIRCUITS CONTAINING INDUCTANCE / 55 AC PARALLEL CIRCUITS CONTAINING INDUCTANCE AND CAPACITANCE / 63 AC POWER, POWER FACTOR, AND POWER FACTOR CORRECTION / 73 v vi Contents 10 SUMMARY REVIEW OF UNITS 1–9 / 85 11 INSTALLATION OF SINGLE-PHASE, THREE-WIRE ENTRANCE FOR A SINGLE-FAMILY RESIDENCE / 91 12 INSTALLATION OF A SINGLE-PHASE, THREE-WIRE SERVICE ENTRANCE FOR AN APARTMENT BUILDING / 105 13 INSTALLATION OF A THREE-PHASE, THREE-WIRE SERVICE ENTRANCE / 115 14 INTRODUCTION TO FLUORESCENT LIGHTING / 125 15 INSTALLATION OF FLUORESCENT LIGHTING / 133 16 SUMMARY REVIEW OF UNITS 11–15 / 145 APPENDIX / 149 GLOSSARY / 151 INDEX / 153 PREFACE The ninth edition of ELECTRICITY has been updated to reflect current materials and techniques in electrical applications, while maintaining the features that have made the text so popular through previous editions Summary statements are found at the end of each unit, and several new problems have been included in the Achievement Review sections ELECTRICITY helps the student achieve a basic understanding of the characteristics of alternating-current circuits and the devices contained in the circuits The knowledge obtained by a study of this text permits the student to progress to further study It should be realized that both the development of the subject of electricity and the study of the subject are continuing processes The electrical industry constantly introduces new and improved devices and materials, which in turn often lead to changes in installation techniques Electrical codes undergo periodic revisions to upgrade safety and quality in electrical installations The text is easy to read and the topics are presented in a logical sequence The problems provided in the text require the use of simple algebra and simple trigonometry for their solutions The student is advised that electron movement (from negative to positive) is used in this text to define current direction Each unit begins with objectives to alert students to the learning that is expected as a result of studying the unit An Achievement Review at the end of each unit tests student understanding to determine if the objectives have been met Following selected groups of units (Units 1–9 and 11–15), a Summary Review unit contains additional questions and problems to test student comprehension of a block of information This combination of reviews is essential to the learning process required by this text All students of electricity will find this text useful, especially those in electrical apprenticeship programs, trade and technical schools, and various occupational programs The most recent edition of the National Electrical Code® (published by the National Fire Protection Association [NFPA]) should be available for reference as the student uses ELECTRICITY Applicable state and local regulations should also be consulted when executing actual installations Features of the ninth edition include • Summary statements in all units • Up-to-date content reflecting current methods and materials of the trade • Currency with the most recent edition of the National Electrical Code® • Detailed problem solutions in most units • Achievement Reviews that reinforce concepts • Practical problems to test student learning • Numerous new problems for student practice Instructor’s Guides for ELECTRICITY through ELECTRICITY are available The guides include the answers to the Achievement Reviews and Summary Reviews for each text and additional test questions covering the content of each text Instructors can use these questions to devise tests to evaluate student learning vii viii Preface ABOUT THE AUTHOR Dr Thomas Kubala received an AAS degree in Electrical Technology from Broome Community College, Binghamton, New York; a BS degree in Electrical Engineering from the Rochester Institute of Technology, Rochester, New York; and an MS degree in Vocational-Technical Education from the State University of New York at Oswego, New York He earned his doctoral degree from the University of Maryland, College Park, Maryland Dr Kubala has served as a full-time faculty member at two community colleges and a department head supervising a vocational-technical program In addition to his extensive background in technological education, Dr Kubala has industrial experience with responsibilities in the fields of aerodynamics, electrical drafting, electrical circuit design, equipment testing, and systems evaluation ACKNOWLEDGMENTS The revision of ELECTRICITY was based on information and recommendations submitted by the following instructors: Phillip Serina, Kaplan Career Institute, Brooklyn, Ohio Silas Qualls, Mountain Empire Community College, Big Stone Gap, Virginia ELECTRICAL TRADES The Delmar series of instructional material for the electrical trades includes the texts, text workbooks, and related information workbooks listed below Each text features basic theory with practical applications and student involvement in hands-on activities ELECTRICITY ELECTRICITY ELECTRICITY ELECTRICITY ELECTRIC MOTOR CONTROL ELECTRIC MOTOR CONTROL LABORATORY MANUAL INDUSTRIAL MOTOR CURRENT ALTERNATING CURRENT FUNDAMENTALS ELECTRICAL WIRING— RESIDENTIAL ELECTRICAL WIRING— COMMERCIAL ELECTRICAL WIRING— INDUSTRIAL PRACTICAL PROBLEMS IN MATHEMATICS FOR ELECTRICIANS Equations based on Ohm’s law E E = IR I = E R I R R = E I P = IE P I = P E I E E = P I NOTE: In this text, E is used to denote a voltage source, and V is used for a voltage drop ix 142 Unit 15 Installation of Fluorescent Lighting The type of fluorescent lamp that can be used for dimming is the a rapid-start d ballast lamp b preheat e instant-start c glow lamp The fastest starting and slowest starting lamps, respectively, are the a rapid-start and instant-start d instant-start and rapid-start b rapid-start and preheat e preheat and rapid-start c instant-start and preheat The slimline lamp is a a rapid-start lamp d a ballast lamp b an instant-start lamp e a glow lamp c a preheat lamp A separate starter and socket is required for the fluorescent lamp type called a instant-start d rapid-start b glow e preheat c slimline The type of lamp that has the cathodes heated continuously before the lamp is to be lighted is the a slimline d preheat b rapid-start e ballast c instant-start The type of lamp that has a single terminal pin at each end is the a rapid-start d instant-start b preheat e filament c glow Fluorescent lamps a cannot be used in low-temperature environments b can use almost any type of starter c can be used with any type of ballast d should be operated continuously for periods of to hours e should be turned on and off as often as possible to increase lamp life 10 If a fluorescent lamp shows a dense blackening at each end, even though the lamp was used correctly in a proper circuit with appropriate components, it means that a the ballast is the wrong size b the voltage is too low c the lamp is at the end of its useful life d the fixture is improperly wired e the starter is the wrong size Unit 15 Installation of Fluorescent Lighting 143 For items 11 through 14, answer T for True and F for False 11 The fluorescent lamp that was developed to overcome the delayed lighting with preheat units was the instant-start lamp 12 For preheat fluorescent lamps, the physical length will increase as the rated wattage is increased for lamps above 20 watts 13 The slimline fluorescent lamp was designed for instant starting 14 The type of lamp that has a single terminal pin at each end is the glow lamp This page intentionally left blank U•N•I•T 16 SUMMARY REVIEW OF UNITS 11–15 OBJECTIVE • To evaluate the knowledge and understanding acquired in the study of the previous five units POINTS TO REMEMBER • To determine the number of residential lighting circuits, the volt-amperes per square foot method is applied, and the outside dimensions of the building are used for the calculation • To determine the number of small appliance circuits, an additional load of not less than 1,500 watts shall be included for each circuit • The purpose of bonding on service-entrance equipment is to ensure a low impedance path to ground should a fault occur on any of the service-entrance conductors • To achieve maximum lamp life with fluorescent tubes, avoid turning them on and off frequently In items through 25, select the best answer to make each incomplete statement true Place the letter of the selected answer in the space provided The minimum number of volt-amperes per square foot allowed by the Code® in determining the lighting load for a single-family dwelling is a b c d The voltage from one ungrounded conductor to another ungrounded conductor in a normal three-wire installation for a single-family dwelling is a 120 volts c 240 volts b 150 volts d 460 volts The minimum number of small appliance circuits permitted by the Code® for a single-family home is a b c d 145 146 Unit 16 Summary Review of Units 11–15 The minimum size AWG wire that is permitted for small-appliance circuits in a home is a b 10 c 12 d 14 For a single-family dwelling, the service ground wire is attached to the street side of the water meter a for maximum safety b because it is an easy installation c only for certain types of homes d only when the service exceeds 50 amperes The minimum number of volt-amperes per square foot allowed by the Code® in determining the lighting load for apartment dwellings is a b c d The minimum load in watts that must be allowed for small appliances in apartment dwellings is a kW b kW c kW d kW The minimum size feeder wire that can be used for a three-wire feeder supplying more than two two-wire branch circuits is a No AWG c No 12 AWG b No 10 AWG d No 14 AWG For a computed neutral load of 234 amperes, the minimum size of the RHW neutral wire is a 250 Kcmil c No 1/0 b 300 Kcmil d No 2/0 10 The meter that records the amount of energy used is the a wattmeter c voltmeter b watt-hour meter d ohmmeter 11 An employee of the local power company is the only person who is permitted to install the a bonding c power panel b branch circuits d watt-hour meter 12 The minimum size of TW wires required for a motor that has a current rating of 27 amperes is a 1/0 AWG c No AWG b No AWG d No 10 AWG Unit 16 Summary Review of Units 11–15 147 13 The maximum size of time-delay fuses for branch-circuit protection for the motor in problem 12 should be a 40-ampere c 100-ampere b 50-ampere d 120-ampere 14 The oldest type of fluorescent lamp is the a rapid-start c ballast b instant-start d preheat 15 The type of fluorescent lamp that can be used in flashing circuits is the a rapid-start c ballast b instant-start d preheat 16 Another name for the instant-start lamp is a thinline c slimline b ballast d thin tube 17 Fluorescent lamps can be used a in temperatures above 50°F b only indoors c only in dry weather conditions d in almost any type of weather condition 18 When fluorescent lamps are used to replace incandescent bulbs, usually a greater illumination occurs b less illumination occurs, but they look better c only one color can be obtained d more shadows occur, but there is less eyestrain 19 When a fluorescent lamp shows a dense blackening at each end, it could possibly mean that the a gas is old b lamp was started infrequently c starter is working improperly d lamp is new 20 When a capacitor is used in a fluorescent lamp circuit to correct power factor, the power factor approaches a 0.5 percent c 80 percent b 1.0 percent d 100 percent 21 The ballast lamp performs the same function as the a glow tube c starter b reactor coil d preheat fluorescent lamp 148 Unit 16 Summary Review of Units 11–15 22 One advantage of a preheat fluorescent lamp as compared to an incandescent lamp is that it a illuminates faster b provides less illumination per watt of power c generally has a longer life d can be used for heating as well as lighting 23 Modern two-lamp, rapid-start circuits have the lamps connected a in series c in a series-parallel combination b in parallel d to separate glow lamps 24 A typical gas that is used in fluorescent lamps is a oxygen c xenon b nitrogen d argon-neon 25 One of the reasons the instant-start fluorescent lamp was developed was to a simply provide variety b overcome the delayed starting that occurs with the preheat type c provide the capabilities of dimming that could not be obtained with incandescent lamps d have a slower starting lamp than the rapid-start lamp 26 A single-family dwelling has an active area of 1,700 square feet, and an 8-kW, 120/240-volt range is to be installed Using the minimum number of volt-amperes per square foot permitted by the Code®, determine the necessary number of 120-volt, two-wire branch lighting circuits _ _ _ _ _ _ 27 The number of small appliance circuits required for the dwelling in problem 26 is _ 28 Referring to problem 26, determine the size of TW wires for the oven branch circuit _ _ _ _ APPENDIX 149 150 Appendix Electrical wiring symbols (From Ray G Mullin, Electrical Wiring Residential, 13th edition [Delmar Publishers 1999]) GLOSSARY ANTIRESONANCE Resonance in a parallel circuit, which occurs when the inductive current equals the capacitive current APPARENT POWER AWG Volt-amperes; volts multiplied by amperes American Wire Gauge BONDING The permanent joining of metallic parts to form an electrically conductive path CAPACITANCE (C) The property of a capacitor relating to electrical charge; created by electrons CAPACITIVE REACTANCE (XC) The amount of current change opposition FARAD (F) or MICROFARAD (µF) FREQUENCY (f) GROUND Unit of capacitance The rate at which a cycle repeats itself; cycles per second A connection to the earth, or a conducting device that serves in place of the earth HERTZ (Hz) The unit of frequency in cycles per second IMPEDANCE (Z) INDUCTANCE (L) The combined opposition to current The property of a coil that opposes any change in current INDUCTIVE REACTANCE (XL) is caused by an inductance The amount of opposition to current change Similar to XC but LAGGING The current lags behind the voltage; an inductive circuit LEADING The current leads the voltage; a capacitive circuit PHASE RELATIONSHIP POWER (P) Rate of doing work, or the rate at which energy is used POWER FACTOR (PF) RESONANCE VECTOR The angle between current and voltage in a vector diagram The ratio of power to apparent power A series circuit condition where XL = XC A straight line that represents magnitude and direction of current or voltage 151 This page intentionally left blank INDEX Numbers 1-phase service installations, 91–114 See also under individual topics apartment buildings, 105–113 single-family residences, 91–103 1-pole switches, 150 1-receptacle outlets, 92–93 2-lamp circuits, 134–138 2-pole switches, 150 2-receptacle outlets, 93 2-resistor circuits, 29 2-wire cables and raceways, 149 3-phase service installations, 115–121 See also Three-phase three-wire service entrances 3-receptacle outlets, 93 3-way switches, 150 3-wire cables and raceways, 149 3-wire service installations, 92 See also Three-wire service installations 4-way switches, 150 4-wire cables and raceways, 149 A AC (alternating current), 1–10, 55–81 See also under individual topics parallel circuits, 55–71 inductance, 11–17, inductance and capacitance, 45–53, 63–71 power, power factors, and power factor correction, 73–90, 128 principles, 1–10 alternators, cycles, 2–6 degrees, mechanical vs electrical, effective values, 6–8 EMF, 1–2, frequencies, 5–6 lag and lagging, lead and leading, objectives, overviews and summaries, 7–8 in phase vs out of phase, reviews, 8–10 single phase voltage, voltage generation, 7–8 Achievement reviews See Reviews Air conditioner circuits, 94 Alternating current See AC (alternating current) Alternators, American Wire Gauge See AWG (American Wire Gauge) Annunciators, 149 Antiresonance, 67–68 Apartment building installations, 105–113 See also Single-phase three-wire services Apparent power, 78, 81 Appliance circuits, 93, 96, 106 Argon and argon-neon gasses, 126 Autotransformer ballast single lamps, 134–135 AWG (American Wire Gauge), 151 B Batteries, 149 Bells, 149 Bonding, 100–101 Branch lighting circuits, 106 Breakers, 98, 100, 112 Buzzers, 149 C Capacitance and capacitive reactance, 19–28 calculations, 20–21 capacitors, 19–28 electrolytic, 24 oil-filled, 19–21 dielectrics, 19 farads and microfarads, 20 objectives, 19 overviews and summaries, 24 parallel circuits, 63–69 See also Parallel circuits, 20, 22–23 reviews, 24–28 series circuits, 29–54 See also Series circuits Capacitors, 19–28 Ceiling outlets, 92 Chimes, 149 Circuit breakers, 98, 118 Circuit-device-material topics See Electricity (devicecircuit-material) topics Clocks, 149 Coil turns, 12 Conductors and conductor sizes, 108 Convenience outlets, 92 Cooking unit circuits, 94 Current lag See Lag and lagging Current lead See Lead and leading Cycles, 2–5 D DC (direct current) circuits, 73 Definitions and terminology, 151 Degrees, mechanical vs electrical, Device-circuit-material topics See Electricity (devicecircuit-material) topics Dielectrics, 19 Direct current circuits See DC (direct current) circuits Dishwasher circuits, 93 Disposal circuits, 93 Distribution panels, 105, 116 Door chimes, 149 Door openers, 149 Door switches, 150 Double-pole switches, 150 Duplex receptacle outlets, 149 E Effective values, 6–7 Electric door openers, 149 Electric space heating circuits, 95 Electrical symbols, 149–150 Electricity (device-circuit-material) topics See also under individual topics AC (alternating current), 1–10, 55–81 parallel circuits (inductance), 55–61 parallel circuits (inductance and capacitance), 63–71 power, power factors, and power factor correction, 73–90, 128 principles, 1–10 capacitance and capacitive reactance, 19–28 fundamental concepts, vii–ix See also Overviews and summaries inductance and inductive reactance, 11–17 installations, 91–143 fluorescent lighting, 125–143 single-phase three-wire services (apartment buildings), 105–113 single-phase three-wire services (single family residences), 91–103 three-phase three-wire service entrances, 115–123 objectives See Objectives reviews, 85–90 See also Reviews series circuits, 29–53 resistance, inductance, and capacitance, 45–54 resistance and capacitance, 37–43 resistance and inductance, 29–36 Electrolytic capacitors, 24 EMF (electromotive force), 1–2, 153 154 Index F Fan outlets, 149 Farads, 20 Feeders and feeder fuses, 116–117 Fluorescent lighting, 125–143 fundamental concepts, 125-130 advantages, 125 basic circuits, 126–128 objectives, 125 overviews and summaries, 129 power factor correction, 128–129 reviews, 129–131 tubes, preheat types, 126–128 installation, 133–143 appearance problems, 141 autotransformer ballast single lamps, 134–135 instant-start lamps, 133, 136–139 lamp maintenance, 139–141 objectives, 133 overviews and summaries, 133, 141 preheat lamps, 126–129 rapid-start lamps, 133, 139 reviews, 141–143 slimline instant-start lamps, 136–138 starting problems, 140–141 two-lamp circuits, 134–138 symbols, 149 Four-way switches, 150 Four-wire cables and raceways, 149 Frequencies, 5–6 Fundamental concepts, vii–ix, 1–10 See also Overviews and summaries Fuses, 117–118 G Garbage disposal circuits, 93 Glossary, 151 Glow switches and tubes, 126 Ground connections, 99–100 Ground fault protection, 117–118 H Heating panels, 149 Hertz, 5, 8, 35, 151 I Impedance, 29–33, 37–39, 57, 59 Inductance and inductive reactance, 11–17 coil turns, 12 effects, 12 EMF, 11–12 lag and lagging, 13 Lenz’s law, 11–13 measurements, 12 mutual inductance, 11–12 objectives, 11 overviews and summaries, 11, 14 parallel circuits, 55–71 See also Parallel circuits reviews, 15–17 self-inductance, 11–12 series circuits, 29–53 See also Series circuits step-up transformers, 12 vector analyses, 13–14 Industrial load, 116–121 Installations, 91–123, 133–141 See also under individual topics fluorescent lighting, 125–141 single-phase three-wire services, 91–113 apartment buildings, 105–113 single-family residences, 91–103 three-phase three-wire service entrances, 115–123 Instant-start lamps, 133, 136–139 J Junction boxes, 149 K Krypton gas, 126 L Lag and lagging, 7, 13, 68 Lampholders with pull switches, 149 Laundry circuits, 93 Laws, ix, 11–13, 23, 32–33, 57 Lenz’s, 11–13 Ohm’s, ix, 23, 32–33, 57 Lead and leading, 7, 21–22 Lenz’s law, 11–13 Lighting, 92–93 circuits, 92–93 fluorescent See Fluorescent lighting panels, 105 Load, 107–109, 116–121 computations, 107–109 industrial, 116–121 M Material-device-circuit topics See Electricity (devicecircuit-material) topics Mechanical vs electrical degrees, Meter socket boxes, 119–121 Meter test cabinets, 119 Microfarads, 20 Motor symbols, 149 Multioutlet assemblies, 150 Mutual inductance, 11–12 N NEC® (National Electrical Code® ), vii, 92 Neutrals, 109–110 service-entrance, 110 subfeeders, 109 NFPA (National Fire Protection Association), vii O Objectives See also under individual topics AC principles, 1–10 capacitance and capacitive reactance, 19–28 fluorescent lighting, 125–143 fundamental concepts, 125 installation, 133–143 inductance and inductive reactance, 11–17 installations, 91–123, 133–143 single-phase three-wire services (apartment buildings), 105–113 single-phase three-wire services (singlefamily residences), 91–103 three-phase three-wire service entrances, 115–123 parallel circuits, 55–71 inductance and capacitance in parallel, 63 inductance in parallel, 55 power, power factors, and power factor correction, 73–84 series circuits, 29–53 resistance, inductance, and capacitance in series, 45–53 resistance and capacitance in series, 37–43 resistance and inductance in series, 29–36 Ohm’s law, ix, 14, 23, 32–33, 57 Oil-filled capacitors, 19–21 Out of phase, See also Lag and lagging; Lead and leading Oven circuits, 94 Overcurrent devices, 111 Overviews and summaries See also under individual topics AC principles, 1–10 capacitance and capacitive reactance, 19–28 fluorescent lighting, 125–143 fundamental concepts, 125 installation, 133–143 inductance and inductive reactance, 11–17 installations, 91–123, 133–143 single-phase three-wire services (apartment buildings), 105, 112 single-phase three-wire services (singlefamily residences), 91–103 three-phase three-wire service entrances, 115–123 parallel circuits, 55–71 inductance and capacitance in parallel, 63 inductance in parallel, 55 power, power factors, and power factor correction, 73–84 series circuits, 29–53 Index resistance, inductance, and capacitance in series, 45–53 resistance and capacitance in series, 37–43 resistance and inductance in series, 29–36 P Parallel circuits, 55–71 inductance and capacitance in parallel, 63 antiresonance, 67–68 lag and lagging, 7, 68 objectives, 63 overviews and summaries, 63, 68–69 reviews, 69–71 unequal reactance, 66–67 inductance in parallel, 55–61 impedance, 29, 57–59 objectives, 55 Ohm’s law, 57 overviews and summaries, 55, 59 reviews, 59–61 vector analyses, 55–59 Phase relationships, 32–33, 38–40, 45–49 Power, power factors, and power factor correction, 73–84 AC circuits, 73–77 DC circuits, 73 measurements, 80–81 objectives, 73 overviews and summaries, 73, 81 power factor correction, 78–80 power factors, 77–78, 80–81 reviews, 82–84 wattmeters, 80–81 Power distribution panels, 116 Power panels, 146 Pre-work procedures, 115–116 Preheat lamps, 134–136 Push buttons, 128 R Range outlets, 103, 107–108 Rapid-start lamps, 133, 139 RC circuits See Resistance in series Reactance, 11–28, 45–50 See also under individual topics capacitance and capacitive reactance, 19–28 inductance and inductive reactance, 11–18 Recessed fixture ceiling outlets, 149 Resistance in series, 29–53 See also Series circuits resistance, inductance, and capacitance, 45–53 resistance and capacitance in series, 37–43 resistance and inductance in series, 29–36 Resistor-coil circuits, 29–33 See also Resistance in series Resonance, 45–49 Reviews See also under individual topics AC principles, 1–10 capacitance and capacitive reactance, 19–28 fluorescent lighting, 125–143 fundamental concepts, 125 installation, 133–143 inductance and inductive reactance, 11–17 installations, 91–123, 133–143 single-phase three-wire services (apartment buildings), 105–113 single-phase three-wire services (singlefamily residences), 91–103 three-phase three-wire service entrances, 115–123 parallel circuits, 55–71 inductance and capacitance in parallel, 63 inductance in parallel, 55–61 power, power factors, and power factor correction, 73–84 series circuits, 29–53 resistance, inductance, and capacitance in series, 45–53 resistance and capacitance in series, 37–40 resistance and inductance in series, 29–33 summary, 81 RHW wire, 97–100, 110–111 RL circuits, 37–68 See also Parallel circuits; Series circuits parallel, 55–61 series, 37–44 RLC circuits, 45–54 See also Series circuits S Self-inductance, 11–12 Series circuits, 29–54 resistance, inductance, and capacitance in series, 45–53 objectives, 45 overviews and summaries, 45, 50 phase relationships, 45–49 reactance, 45–49 resonance, 45–49 reviews, 50–53 vector analyses, 45–49 resistance and capacitance in series, 37–43 impedance, 37–39 objectives, 37 overviews and summaries, 37, 40 phase relationships, 38–40 reviews, 40–43 vector analyses, 38–39 155 resistance and inductance in series, 29–36 impedance, 29–33 objectives, 29 Ohm’s law, 32–33 overviews and summaries, 29, 33 phase relationships, 32–33 resistor-coil circuits, 29–33 reviews, 34–36 two-resistor circuits, 29–31 Service entrance installations, 115–121 See also Three-phase three-wire service entrances Short circuit protection, 117–118 Single-family residence installations, 91–103 See also Single-phase three-wire services Single-phase three-wire services, 91–113 See also under individual topics apartment buildings, 105–113 branch lighting circuits, 106–107 conductors, 109–110 ground connections, 111–112 load computations, 107–108 neutrals, service-entrance, 110 neutrals, subfeeders, 109 objectives, 105 overviews and summaries, 105, 112 reviews, 112–113 small appliance circuits, 106–107 subfeeders, 106–109 switches, 111 typical configurations, 105–113 single-family residences, 91–103 air conditioner circuits, 94 bonding, 100–101 branch circuit summaries, 96 conductor sizes, 96–98 counter-mounted cooking unit circuits, 94 dishwasher circuits, 93 dryer circuits, 93–94 electric space heating circuits, 95 garbage disposal circuits, 93 ground connections, 99–100 laundry circuits, 93 lighting circuits, 92–93 objectives, 91 overviews and summaries, 91, 101 reviews, 101–103 small appliance circuits, 93 switches, 98–99 typical configurations, 92–101 wall-mounted oven circuits, 94 water heater circuits, 94–95 Single phase voltage, Single-pole switches, 150 Single receptacle outlets, 93 Slimline instant-start lamps, 136–138 Small appliance circuits, 93, 106–107 Socket boxes, 119–121 Space heating circuits, 95 156 Index Special purpose outlets, 149 Split circuit duplex receptacle outlets, 149 Starters, 126–128 Starting switches, 126–128 Step-up transformers, 12 Subfeeders, 106–107 Summary concepts See Overviews and summaries Switch-fuse combinations, 150 Switch leg indications, 149 Switch-pilot combinations, 150 Switches, 98–99, 111, 118–119 Symbols, 149–150 T Television outlets, 149 Terminology and definitions, 150 Test cabinets, 119–121 Thermal overloads, 150 Thermostats, 95 Three-phase three-wire service entrances, 115–123 feeders and feeder fuses, 117–118 industrial load, 116–121 meter socket boxes, 119–121 meter test cabinets, 119–121 objectives, 115 overviews and summaries, 115, 121 pre-work procedures, 115–116 reviews, 121–123 short circuit and ground fault protection, 117–118 switches, 118–119 watt-hour meters, 121 Three-way switches, 150 Three-wire cables and raceways, 149 Three-wire service installations See also under individual topics single-phase, 91–113 apartment buildings, 105–113 single-family residents, 105–113 three-phase entrances, 115–123 THW wire, 97 Transformers, 12 Triplex receptacle outlets, 149 Turns, coil, 12 Two-lamp circuits, 134–136 Two-resistor circuits, 29–31 Two-wire cables and raceways, 149 U Unequal reactance, 66–67 V Vectors and vector analyses, 13–14, 38–40, 45–50, 57–59 Volt-amperes, 78 Voltage generation, 1–4 W Wall brackets, 149 Wall-mounted oven circuits, 94 Water heater circuits, 94–95 Watt-hour meters, 121 Wattmeters, 80–81 Weatherproof receptacle outlets and switches, 149–150 [...]... = 60 Hz C = 13 µF 1,000,000 XC = = 20 4 Ω 2 × 3.14 × 60 × 13 f = 60 Hz C = 26 µF XC = Capacitor C 1,000,000 = 1 02 Ω 2 × 3.14 × 60 × 26 f = 120 Hz C = 26 µF XC = 1,000,000 = 51 Ω 2 × 3.14 × 120 × 26 Unit 3 Capacitance and Capacitive Reactance CAPACITOR f (Hz) C (µF) XC (Ω) A B C 60 60 120 13 26 26 20 4 1 02 51 21 Capacitive reactance varies indirectly with capacitance and frequency Capacitive reactance... purely inductive circuit (no resistance), a current lags voltage b voltage lags current by 90° c current and voltage are in phase d voltage leads current e current lags voltage by 90° 6 The inductive reactance of a 0.06-H coil connected to a 120 -V, 60-Hz source is a 2. 26 Ω c 7 .2 Ω e 4 32 Ω b 3.6 Ω d 22 . 62 Ω 16 Unit 2 Inductance and Inductive Reactance 7 A purely inductive circuit contains... source of 28 0 V at 40 Hz The total inductive reactance of the circuit is 20 Ω The value of the total current, in amperes, is a 0.056 d 7.0 b 0.08 e 14.0 c 2. 0 8 A current of 5 A exists in a purely inductive circuit connected to a 120 -V, 60-Hz source The total inductive reactance of the circuit shown in Figure 2- 7 is a 0.064 H Figure 2- 7 5A Inductive reactance b 12. 0 Ω 120 V E c 24 .0 Ω 60... 110/50 = 2. 2 inches The scale for the current vector is 1 inch = 10 amperes 110 V E 90° 10 A 14 I FINDING CURRENT Figure 2- 5 and the following example show how current is determined in an AC inductive circuit Figure 2- 4 Vector diagram of current lagging voltage by 90° First, find XL: XL = 2 fL = 2 × 3.14 × 60 × 0.3 120 V 60 Hz L 0.3 H E Using Ohm’s law, I Figure 2- 5 Inductive circuit = 113.1 Ω = E = 120 ... capacitive circuit C 88.5 µF Unit 3 Capacitance and Capacitive Reactance Using Ohm’s law: I = E = 120 XC 30 =4A CALCULATING CAPACITANCE AND CURRENT In Figure 3-6, the capacitance of the circuit must be found to determine the total circuit current Find the combined capacitance of C2 and C3 C2,3 = 25 µF + 35 µF = 60 µF C2,3 is the series equivalent of the two parallel capacitors Therefore, the circuit becomes... the circuit becomes a series circuit as shown in Figure 3-7 The total capacitance is found with the following formulas: 1 = 1 + 1 Ct C 1 C 2, 3 or C t = C1 × C 2, 3 C1 + C 2, 3 C1 40 µF 120 V 60 Hz C2 25 µF E C3 35 µF Figure 3-6 Finding current C1 40 µ F 120 V 60 Hz E Figure 3-7 Series equivalent circuit Therefore, 1 = 1 + 1 = 0. 025 + 0.01666 Ct 40 60 1 = 0.04166 or C = 1 = 24 µ t Ct 0.04166 1,000,000... 1,000,000 = = 1,000,000 2 × 3.14 × 60 × 24 9,043 .2 2πfC Using Ohm’s law: I t = E = 120 = 1.08 A X C t 110.6 C 2, 3 60 µ F 23 24 Unit 3 Capacitance and Capacitive Reactance The alternate solution for Ct is: C t = 40 × 60 = 24 µF 40 + 60 Figure 3-8 An AC electrolytic capacitor SUMMARY Capacitors are built to store an electrical charge Capacitance is the property of a capacitor, and capacitive reactance... inductance in Figure 2- 6? 140 V 80 Hz 0.7 A E L Figure 2- 6 Finding inductance X L = E = 140 = 20 0 Ω I 0.7 X L = 2 fL 20 0 L = XL = 2 f 2 × 3.14 × 80 L = 20 0 = 0.398 H 5 02. 4 SUMMARY Inductance is the property of a coil of wire The frequency of current passing through the coil helps to determine the inductive reactance of that coil Inductive reactance is similar to resistance in a circuit because it opposes... frequency and inductance are known, the opposition, or inductive reactance (XL), can be calculated XL = 2 fL Where XL = inductive reactance in ohms π = 3.14 f = frequency in hertz L = inductance in henrys Examples: Coil A Coil B f XL f XL = = = = 60 Hz L = 0.1 H 2 × 3.14 × 60 × 0.1 = 37.7 Ω 60 Hz L = 0 .2 H 2 × 3.14 × 60 × 0 .2 = 75.4 Ω If Coil B is connected to 120 Hz: XL = 2 × 3.14 × 120 × 0 .2 = 150.7... the coils have mutual inductance Figure 2- 1 illustrates a transformer containing a primary coil and a secondary coil The primary coil contains a current that creates 11 12 Unit 2 Inductance and Inductive Reactance IRON CORE PRIMARY SECONDARY 22 0 V INDUCED 120 V IMPRESSED SELF-INDUCTANCE MUTUAL INDUCTANCE Figure 2- 1 Transformer showing location of self-inductance and mutual inductance a magnetic field ... 44 .2 Ω 22 ,608 Using the impedance formula Z = Z= R2 + XC2 , 30 + 44 .2 = 900 + 1,954 = Z = 53.4 Ω Using Ohm’s law, I = E = 120 = 2. 25 A Z 53.4 For the voltages, ER = IR and EC = IXC ER = 2. 25... relationship Unit Series Circuit: Resistance and Capacitance 39 If ET and EC are known, ER can be found as follows: E R2 + E C2 = E T2 E R2 = E T2 − E C2 ER = E T2 − E C2 Using the values in Figure... connected to a 120 -V, 60-Hz source is a 2. 26 Ω c 7 .2 Ω e 4 32 Ω b 3.6 Ω d 22 . 62 Ω 16 Unit Inductance and Inductive Reactance A purely inductive circuit contains a voltage source of 28 0 V at 40