Tài liệu Lessons In Electric Circuits, Volume II – AC

Lessons In Electric Circuits, Volume II – AC By Tony R. Kuphaldt

Lessons In Electric Circuits, Volume II - ACBy Tony R. Kuphaldt

Sixth Edition, last update July 25, 2007

Contents
1 BASIC AC THEORY 1
1.1 What is alternating current (AC)? 1
1.2 AC waveforms . 6
1.3 Measurements of AC magnitude . 11
1.4 Simple AC circuit calculations 18
1.5 AC phase 20
1.6 Principles of radio . 22
1.7 Contributors 24
2 COMPLEX NUMBERS 27
2.1 Introduction 27
2.2 Vectors and AC waveforms 30
2.3 Simple vector addition 32
2.4 Complex vector addition . 35
2.5 Polar and rectangular notation 36
2.6 Complex number arithmetic . 41
2.7 More on AC polarity 43
2.8 Some examples with AC circuits . 48
2.9 Contributors 54
3 REACTANCE AND IMPEDANCE { INDUCTIVE 55
3.1 AC resistor circuits 55
3.2 AC inductor circuits 57
3.3 Series resistor-inductor circuits 61
3.4 Parallel resistor-inductor circuits . 68
3.5 Inductor quirks 71
3.6 More on the skin e®ect . 74
3.7 Contributors 76
4 REACTANCE AND IMPEDANCE { CAPACITIVE 79
4.1 AC resistor circuits 79
4.2 AC capacitor circuits . 81
4.3 Series resistor-capacitor circuits . 85
4.4 Parallel resistor-capacitor circuits 90
4.5 Capacitor quirks 93
4.6 Contributors 95
5 REACTANCE AND IMPEDANCE { R, L, AND C 97
5.1 Review of R, X, and Z 97
5.2 Series R, L, and C . 98
5.3 Parallel R, L, and C 104
5.4 Series-parallel R, L, and C 108
5.5 Susceptance and Admittance . 116
5.6 Summary 117
5.7 Contributors 117
6 RESONANCE 119
6.1 An electric pendulum . 119
6.2 Simple parallel (tank circuit) resonance . 124
6.3 Simple series resonance 129
6.4 Applications of resonance . 133
6.5 Resonance in series-parallel circuits . 134
6.6 Q and bandwidth of a resonant circuit . 143
6.7 Contributors 149
7 MIXED-FREQUENCY AC SIGNALS 151
7.1 Introduction 151
7.2 Square wave signals 156
7.3 Other waveshapes . 166
7.4 More on spectrum analysis 172
7.5 Circuit e®ects . 183
7.6 Contributors 186
8 FILTERS 187
8.1 What is a ¯lter? 187
8.2 Low-pass ¯lters 188
8.3 High-pass ¯lters 194
8.4 Band-pass ¯lters 198
8.5 Band-stop ¯lters 200
8.6 Resonant ¯lters 202
8.7 Summary 214
8.8 Contributors 214
9 TRANSFORMERS 215
9.1 Mutual inductance and basic operation . 216
9.2 Step-up and step-down transformers . 229
9.3 Electrical isolation . 235
9.4 Phasing . 237
9.5 Winding con¯gurations 240
9.6 Voltage regulation . 246
9.7 Special transformers and applications 249
9.8 Practical considerations 266
9.9 Contributors 278
Bibliography . 278
10 POLYPHASE AC CIRCUITS 279
10.1 Single-phase power systems 279
10.2 Three-phase power systems 285
10.3 Phase rotation . 291
10.4 Polyphase motor design 296
10.5 Three-phase Y and ¢ con¯gurations . 301
10.6 Three-phase transformer circuits . 308
10.7 Harmonics in polyphase power systems . 313
10.8 Harmonic phase sequences 338
10.9 Contributors 340
11 POWER FACTOR 341
11.1 Power in resistive and reactive AC circuits . 341
11.2 True, Reactive, and Apparent power . 346
11.3 Calculating power factor . 349
11.4 Practical power factor correction . 354
11.5 Contributors 357
12 AC METERING CIRCUITS 359
12.1 AC voltmeters and ammeters . 359
12.2 Frequency and phase measurement 366
12.3 Power measurement 374
12.4 Power quality measurement 376
12.5 AC bridge circuits . 378
12.6 AC instrumentation transducers . 388
12.7 Contributors 397
Bibliography . 397
13 AC MOTORS 399
13.1 Introduction 400
13.2 Synchronous Motors . 404
13.3 Synchronous condenser 412
13.4 Reluctance motor . 413
13.5 Stepper motors . 417
13.6 Brushless DC motor 430
13.7 Tesla polyphase induction motors 434
13.8 Wound rotor induction motors 449
13.9 Single-phase induction motors 453
13.10 Other specialized motors . 458
13.11 Selsyn (synchro) motors . 460
13.12 AC commutator motors . 468
Bibliography . 470
14 TRANSMISSION LINES 473
14.1 A 50-ohm cable? 473
14.2 Circuits and the speed of light 474
14.3 Characteristic impedance . 476
14.4 Finite-length transmission lines 482
14.5 Long and short transmission lines 489
14.6 Standing waves and resonance 492
14.7 Impedance transformation 512
14.8 Waveguides . 520
A-1 ABOUT THIS BOOK 525
A-2 CONTRIBUTOR LIST 529
A-3 DESIGN SCIENCE LICENSE 535
INDEX 538



Most students of electricity begin their study with what is known as direct current (DC), which is electricity °owing in a constant direction, and/or possessing a voltage with constant polarity. DC is the kind of electricity made by a battery (with de¯nite positive and negative terminals), or the kind of charge generated by rubbing certain