Automotive Electrical & Electronic Systems Classroom Manual

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Chapter Eight

There is more current available because all of the voltage has been rectified. This is called full-wave rectification. However, there are still moments when current is at zero. Most automotive AC generators use three conductors and six diodes to produce overlapping current waves so that current output is never at zero. Heat Sinks The term heat sink is commonly used to describe the block of aluminum or other material in which the AC generator diodes are mounted. The job of the heat sink is to absorb and carry away the heat in the diodes caused by electrical current through them. This action keeps the diodes cool and prevents damage. An internal combustion engine is also a heat sink.The engine is designed so that the combustion and friction heat are carried away and dissipated to the atmosphere. Although they are not thought of as heat sinks, many individual parts of an automobile—such as the brake drums—are also designed to do this important job.

Figure 8-9.

Rotor. (DaimlerChrysler Corporation)

AC GENERATOR (ALTERNATOR) COMPONENTS The previous illustrations have shown the principles of AC generator operation. To provide enough direct current for an automobile, AC generators must have a more complex design. But no matter how the design varies, the principles of operation remain the same. The design of the AC generator limits its maximum output. To change this maximum value for different applications, manufacturers change the design of the stator, rotor, and other components. The following paragraphs describe the major parts of an automotive AC generator.

Rotor The rotor carries the magnetic field. Unlike a DC generator, which usually has only two magnetic poles, the AC generator rotor has several north (N) and south (S) poles. This increases the number of flux lines within the AC generator and increases the voltage output. A typical automotive rotor (Figure 8-9) has 12 poles: 6 N and 6 S. The rotor consists of two steel rotor halves, or pole pieces,

Figure 8-10. The flux lines surrounding an 8-pole rotor. (DaimlerChrysler Corporation)

with fingers that interlace. These fingers are the poles. Each pole piece has either all N or all S poles. The magnetic flux lines travel between adjacent N and S poles (Figure 8-10). Keep in mind that an alternator is an AC generator; in some European manufacturers’ service manuals, the AC generator (alternator) is referred to as a generator. Along the outside of the rotor, note that the flux lines point first in one direction and then in the other. This means as the rotor spins inside the AC generator, the fixed conductors are being cut by flux lines, which point in alternating directions. The induced voltage alternates, just as in the example of a simple AC generator with only two poles. Automotive AC generators may have any number of poles, as long as they are placed N-S-N-S. Common designs use eight to fourteen poles. The rotor poles may retain some magnetism when the AC generator is not in operation, but this


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Summary

4min
page 363

Cruise Control Systems

3min
pages 357-358

Review Questions

3min
pages 364-366

Radios and Entertainment Systems

6min
pages 337-339

Theft Deterrent Systems

7min
pages 353-356

Heated Seats

6min
pages 343-345

Power Seats

2min
pages 341-342

Power Door Locks, Trunk Latches, and Seat- Back Releases

2min
page 346

Heating and Air-Conditioning Systems

12min
pages 328-334

Class 2 IPM-Controlled HVAC Systems

2min
pages 335-336

Review Questions

1min
page 326

Summary

1min
page 325

Windshield Wipers and Washers

10min
pages 319-324

Summary

1min
page 314

Review Questions

2min
pages 315-316

Head-Up Display (HUD

5min
pages 311-313

Electromagnetic Instrument Circuits

11min
pages 296-300

Review Questions

2min
pages 293-294

Malfunction Indicator Lamp (MIL

5min
pages 301-303

Summary

1min
page 292

Instrument Panel and Interior Lamp Circuits

4min
pages 289-291

Circuits

1min
page 288

Backup Lamp Circuits Side Marker and Clearance Lamp

1min
page 287

Circuits

2min
page 286

Stop Lamp and Turn Signal Circuits Hazard Warning Lamp (Emergency Flasher)

6min
pages 282-285

Taillamp, License Plate Lamp, and Parking Lamp Circuits

1min
page 281

Common Automotive Bulbs

1min
page 280

Headlamp Circuits

16min
pages 270-279

Summary

1min
page 267

Review Questions

1min
page 268

Spark Plug Construction

4min
pages 264-266

Distributor Cap and Rotor

3min
pages 259-261

Primary and Secondary Circuits

1min
page 248

Voltages

4min
pages 246-247

Basic Circuits and Current

1min
page 241

Silicon-Controlled Rectifiers (SCRs

1min
page 233

Review Questions

2min
pages 236-238

Summary

1min
page 235

Transistors

9min
pages 229-232

Rectifier Circuits

2min
page 228

Semiconductors

7min
pages 222-224

Photonic Semiconductors

2min
page 227

Review Questions

3min
pages 218-220

Starter Motor and Drive Types

8min
pages 210-214

DC Starter Motor Operation

5min
pages 206-208

Summary

2min
pages 216-217

Overrunning Clutch

1min
page 215

Specific Starting Systems

6min
pages 200-203

Summary

2min
pages 191-192

Differences

13min
pages 183-190

Review Questions

3min
pages 193-194

Charge/Voltage/Current Indicators

3min
pages 180-181

Solid-state Regulators

9min
pages 175-179

Electromagnetic Regulators

1min
page 174

Voltage Regulation

2min
page 173

Current Production in an AC Generator

9min
pages 168-172

Diode Rectification

3min
pages 162-163

AC Generator (Alternator) Components

7min
pages 164-167

Review Questions

4min
pages 157-158

Battery Installations

4min
pages 150-151

Battery Installation Components

2min
pages 152-153

Summary

2min
page 156

Battery Life and Performance Factors

5min
pages 154-155

State-of-Charge Indicators Wet-Charged and Dry-Charged

2min
page 147

Battery Electrolyte

2min
page 146

Electrochemical Action

8min
pages 142-145

Review Questions

3min
pages 138-140

Wire Color Coding

2min
pages 121-122

Multiplex Circuits

8min
pages 112-114

Ground Paths

2min
page 111

Connectors and Terminals

5min
pages 108-110

Wire Size

6min
pages 105-107

Wire Types and Materials

2min
page 104

Wiring and Harnesses

2min
pages 102-103

Review Questions

4min
pages 97-100

Parallel Circuit Voltage Drops Calculating Series Circuit Total

1min
page 87

Series and Parallel Circuit Faults

3min
pages 94-95

Series-Parallel Circuits

4min
pages 91-93

Review Questions

2min
page 82

Summary

3min
pages 80-81

Electromagnetism

9min
pages 67-71

Electromagnetic Induction

11min
pages 72-76

Magnetism

2min
page 66

Power

2min
page 56

Capacitance

8min
pages 57-60

Review Questions

2min
pages 62-64

Summary

1min
page 61

Complete Electrical Circuit

3min
pages 52-53

Summary

2min
page 43

Historical Figures in Electricity

2min
page 42

Fire Extinguishers

1min
page 31

Safety Tips for Technicians

2min
pages 25-26

Nuts

1min
page 15

Review Questions

2min
pages 44-46

Electrical Cord Safety

1min
pages 29-30

Safety in Lifting (Hoisting) a Vehicle

2min
pages 27-28
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