Electrical Transformers And Rotating Machines

by Herman, Stephen L.

• ISBN13: 9781401899424
• ISBN10: 1401899420
• Edition: 2nd
• Format: Paperback
• Copyright: 2005-07-21
• Publisher: Cengage Learning

Summary

Now in its Second Edition, this book is an excellent resource for electrical students and professionals who need a comprehensive explanation of theory and practical applications of electrical machines. The book includes nine experiments enabling readers to reinforce the theory discussed earlier. Students begin with a study of magnetism and magnetic induction, single-phase isolation transformers, current transformers, and autotransformers. A unit on three-phase power refreshes the student with basic three-phase connections and calculations before proceeding into three-phase transformers.

Table of Contents

Preface	ix
Unit 1 Magnetism	1	(16)
The Earth Is a Magnet	2	(1)
Permanent Magnets	3	(1)
The Electron Theory of Magnetism	3	(3)
Magnetic Materials	6	(1)
Magnetic Lines of Force	6	(2)
Electromagnetics	8	(3)
Magnetic Measurement	11	(2)
Magnetic Polarity	13	(1)
Demagnetizing	13	(2)
Magnetic Devices	15	(2)
Unit 2 Magnetic Induction	17	(21)
Magnetic Induction	17	(3)
Moving Magnetic Fields	20	(1)
Determining the Amount of Induced Voltage	20	(2)
Lenz's Law	22	(2)
Rise Time of Current in an Inductor	24	(2)
The Exponential Curve	26	(2)
Inductance	28	(2)
Induced Voltage Spikes	30	(8)
Unit 3 Inductance in Alternating-Current Circuits	38	(20)
Inductance	39	(3)
Inductive Reactance	42	(5)
Schematic Symbols	47	(1)
Inductors Connected in Series	47	(1)
Inductors Connected in Parallel	48	(1)
Voltage and Current Relationships in an Inductive Circuit	49	(1)
Power in an Inductive Circuit	50	(3)
Reactive Power	53	(1)
Q of an Inductor	53	(5)
Unit 4 Single-Phase Isolation Transformers	58	(56)
Transformer Formulas	59	(2)
Isolation Transformers	61	(53)
Unit 5 Autotransformers	114	(10)
Determining Voltage Values	115	(1)
Using Transformer Formulas	116	(3)
Current Relationships	119	(5)
Unit 6 Current Transformers	124	(10)
Clamp-On Ammeters	129	(5)
Unit 7 Three-Phase Circuits	134	(28)
Three-Phase Circuits	135	(1)
Wye Connections	136	(4)
Delta Connections	140	(3)
Three-Phase Power	143	(1)
Watts and VARs	143	(1)
Three-Phase Circuit Calculations	144	(9)
Load 3 Calculations	153	(1)
Load 2 Calculations	154	(1)
Load 1 Calculations	155	(1)
Alternator Calculations	156	(1)
Power Factor Correction	156	(6)
Unit 8 Three-Phase Transformers	162	(26)
Three-Phase Transformers	163	(5)
Closing a Delta	168	(1)
Three-Phase Transformer Calculations	169	(6)
Open-Delta Connection	175	(13)
Unit 9 Single-Phase Loads for Three-Phase Transformers	188	(10)
Closed Delta with Center Tap	193	(1)
Closed Delta without Center Tap	194	(1)
Delta-Wye Connection with Neutral	194	(4)
Unit 10 Transformer Installation	198	(15)
Transformer Protection	198	(9)
Determining Conductor Size for a Transformer	207	(6)
Unit 11 Transformer Cooling	213	(10)
Air-Cooled Transformers	213	(4)
Liquid-Cooled Transformers	217	(6)
Unit 12 Transformer Maintenance	223	(14)
Safety Procedures	224	(1)
Entering a Transformer Tank	224	(1)
Maintenance of Small Control Transformers	225	(3)
Large Control Transformers Supplying a Motor Control Center	228	(1)
Small Dry-Type Transformers for Commercial and Industrial Use	228	(1)
Large Industrial Dry-Type Transformers for Use in Unit Substations	229	(1)
Media-Cooled Transformers	230	(1)
Pad-Mounted Oil-Cooled Transformers	231	(1)
Internal Inspection and Maintenance	232	(1)
Insulation Testing	232	(2)
Oil Testing	234	(3)
Unit 13 Harmonics	237	(12)
Harmonic Effects	238	(3)
Circuit Breaker Problems	241	(1)
Buss Ducts and Panel Problems	242	(1)
Determining Harmonic Problems on Single-Phase Systems	242	(3)
Determining Harmonic Problems on Three-Phase Systems	245	(1)
Dealing with Harmonic Problems	245	(1)
Determining Transformer Harmonic Derating Factor	246	(3)
Unit 14 Direct Current Generators	249	(37)
What Is a Generator?	250	(10)
Armature Windings	260	(1)
Brushes	261	(1)
Pole Pieces	261	(1)
Field Windings	261	(1)
Series Generators	262	(3)
Shunt Generators	265	(6)
Compound Generators	271	(1)
Compounding	272	(3)
Countertorque	275	(1)
Armature Reaction	276	(2)
Setting the Neutral Plane	278	(2)
Fleming's Left-Hand Generator Rule	280	(1)
Paralleling Generators	281	(5)
Unit 15 Direct Current Motors	286	(36)
DC Motor Principles	286	(4)
Shunt Motors	290	(2)
Series Motors	292	(2)
Compound Motors	294	(2)
Terminal Identification for DC Motors	296	(1)
Determining the Direction of Rotation of a DC Motor	297	(3)
Speed Control	300	(2)
Field Loss Relay	302	(1)
Horsepower	303	(3)
Brushless DC Motors	306	(3)
Converters	309	(1)
Permanent Magnet Motors	309	(8)
Right-Hand Motor Rule	317	(5)
Unit 16 Alternators	322	(16)
Three-Phase Alternators	322	(3)
The Rotor	325	(2)
The Brushless Exciter	327	(1)
Alternator Cooling	328	(2)
Frequency	330	(1)
Output Voltage	331	(1)
Paralleling Alternators	332	(2)
Sharing the Load	334	(1)
Field Discharge Protection	334	(4)
Unit 17 Three-Phase Motors	338	(51)
Three-Phase Motors	339	(1)
The Rotating Magnetic Field	339	(1)
Synchronous Speed	339	(4)
Connecting Dual-Voltage Three-Phase Motors	343	(7)
Squirrel-Cage Induction Motors	350	(14)
Three-Speed Consequent Pole Motors	364	(5)
Four-Speed Consequent Pole Motors	369	(1)
Wound Rotor Induction Motors	369	(6)
Synchronous Motors	375	(7)
Selsyn Motors	382	(7)
Unit 18 Single-Phase Motors	389	(47)
Single-Phase Motors	389	(1)
Split-Phase Motors	390	(2)
Resistance-Start Induction-Run Motors	392	(7)
Capacitor-Start Induction-Run Motors	399	(1)
Dual-Voltage Split-Phase Motors	400	(3)
Determining Direction of Rotation for Split-Phase Motors	403	(1)
Capacitor-Start Capacitor-Run Motors (Permanent-Split Capacitor Motors)	404	(3)
Shaded-Pole Induction Motors	407	(3)
Multispeed Motors	410	(2)
Single-Phase Synchronous Motors	412	(2)
Repulsion Motors	414	(1)
Construction of Repulsion Motors	414	(3)
Repulsion-Start Induction-Run Motors	417	(3)
Repulsion-Induction Motors	420	(1)
Stepping Motors	420	(8)
Universal Motors	428	(8)
Unit 19 Motor Maintenance and Troubleshooting	436	(18)
Motor Bearings	437	(1)
Direct Current Machines	437	(5)
Testing Alternating Current Motors	442	(1)
Testing Dual-Voltage Motors	443	(11)
Unit 20 Motor Installation	454	(31)
Determining Motor Current	454	(6)
Determining Conductor Size for a Single Motor	460	(3)
Overload Size	463	(3)
Determining Locked-Rotor Current	466	(1)
Short-Circuit Protection	467	(3)
Starter Size	470	(6)
Multiple Motor Calculation	476	(9)
Laboratory Experiments	485	(66)
Experiment 1 Transformer Basics	486	(5)
Experiment 2 Single-Phase Transformer Calculations	491	(7)
Experiment 3 Transformer Polarities	498	(9)
Experiment 4 Autotransformers	507	(6)
Experiment 5 Three-Phase Circuits	513	(5)
Experiment 6 Three-Phase Transformers	518	(17)
Experiment 7 Rotating Magnetic Field	535	(2)
Experiment 8 Three-Phase Dual-Voltage Motors	537	(8)
Experiment 9 Single-Phase Dual-Voltage Motors	545	(6)
Appendix A Greek Alphabet	551	(2)
Appendix B Metals	553	(2)
Appendix C Full-Load Current Direct Current Motors	555	(1)
Appendix D Full-Load Current Alternating Current Single-Phase Motors	556	(1)
Appendix E Full-Load Current Alternating Current Three-Phase Motors	557	(2)
Appendix F NEMA Design Codes for Three-Phase Squirrel-Cage Motors	559	(2)
Answers to Practice Problems	561	(3)
Glossary	564	(8)
Index	572