The document describes the operation of an automotive charging system. It explains that the charging system uses an alternator powered by the engine to generate electricity and recharge the battery. The alternator is belt-driven and contains a rotor that spins inside a stationary stator to produce alternating current, which is then rectified to direct current and regulated by a voltage regulator to safely charge the battery and power vehicle electrical components.

1. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only

2. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only

3. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Alternator
generator that uses mechanical power to
produce electricity
Voltage regulator
controls the output voltage of the alternator
Alternator drive belt
links the engine crankshaft pulley with the
alternator pulley
drives the alternator
Charging System Parts

4. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Charging System Parts
Charge Indicator
ammeter, voltmeter, or warning light
informs driver of the charging system
condition
Harness
wiring connecting the parts of the system
Battery
provides current to initially energize the
alternator field
stabilizes the alternator output

5. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Charging System
Recharges the battery and
supplies electricity when
the engine is running

6. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
 Recharges the battery after cranking
 Supplies the car’s electricity when the engine is
running
 Provides an output voltage slightly higher than the
battery voltage
 Changes the output to meet varying loads

7. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
 Two types:
 DC generator
 AC generator (alternator)

8. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
DC Generator
 Similar to an electric motor
 Stationary magnetic field
 The output conductor unit (armature) spins inside
the field
 Induces current from within the armature

9. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
AC Generator (Alternator)
 Advantages:
 more efficient
 smaller and lighter
 more dependable
 more output at idle

10. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
AC Generator (Alternator) Theory
 The magnetic field rotates
 The output conductors (windings) are stationary
 The field rotates, inducing current in the output
windings

11. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Generator
versus
Alternator

12. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
 Two main parts, rotor and stator
 The rotor is located in the center
 creates a rotating magnetic field when turned by the
drive belt
 The stator is a stationary set of windings
surrounding the rotor
 output winding in the alternator

13. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Alternator Operation
 When the rotor spins, its strong magnetic field cuts
across the stator windings
 Current is induced in the stator windings

14. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Alternator
Operation

15. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
AC Output
 Alternating current flows one way, then the other
 As the rotor turns into one stator winding, current is
induced
 When the same rotor pole moves into the other stator
winding, the current reverses direction

16. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Rectified AC Current
 An automobile’s electrical system requires direct
current (DC), which flows one way
 Alternator output must be rectified (changed) from
AC to DC
 A diode allows current flow in only one direction
 Several diodes are connected into a rectifier circuit

17. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Diode
Acts as a one-way electrical check valve

18. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Diode Operation

19. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only

20. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Rotor
 Field windings mounted on a shaft
 Two claw-shaped pole pieces surround the
windings, increasing magnetic field
 The fingers on one pole piece produce south
magnetic poles
 The fingers on the other pole piece produce north
magnetic poles

21. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Rotor Operation
As the rotor spins, alternating polarity produces
alternating current

22. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Slip Rings
 Mounted on the rotor shaft
 Provide current to the rotor windings
 An external source of electricity is needed to excite
the field

23. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Brushes
 Ride on the slip rings
 Provide a sliding electrical connection
 Feed battery current into the slip rings and rotor
windings
 Springs hold the brushes in contact with the slip
rings

24. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Brushes and Slip Rings

25. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Rectifier
 Six diodes convert stator output to direct current
 Provides full-wave rectification
 Changes both positive and negative outputs into direct
current
 Diode trio may be used to feed power from the stator
to the field (rotor)

26. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Charging Circuit

27. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Stator
 Three groups of windings wrapped around a soft,
laminated iron core (ring)
 Produces an electrical output
 The iron core concentrates the field around the
windings

28. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Stator and Rectifier
A rectifier consists of six
diodes, connected to the
stator windings

29. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Y-Type Stator
 The wire ends from the three windings are
connected to a neutral junction
 Looks like a letter “Y”
 Provides good output current at low speeds

30. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Delta-Type Stator
 The stator wires are connected end to end
 Two circuit paths are formed during each phase of
operation
 Provides high output

31. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Alternator Wiring

32. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Alternator Fan
 Mounted on the front of the rotor shaft
 Draws air through and over the alternator
 Cools the windings and diodes

33. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Pulley and Belt
The crankshaft turns the alternator belt

34. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Types of Belts

35. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Voltage Regulator
 Controls the alternator output voltage
 Changes the amount of current flowing through
the rotor windings
 The engine control module (ECM or PCM) may
serve as the voltage regulator

36. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Internally Regulated Alternator

37. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Voltage Regulators

38. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Electronic Voltage Regulator
Operation
 To increase the alternator output, the regulator
allows more current into the rotor windings
 The magnetic field around the rotor is increased
 More current is induced in the stator windings,
increasing output

39. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Battery Thermistor
 Measures battery temperature
 Allows the charging system to alter output as needed
 A cold battery requires more voltage for charging than
a hot battery
 Often mounted on the positive battery cable

40. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Computer Monitor and Control
 The powertrain control module (PCM) can
supplement or replace the voltage regulator
 The PCM can react to changing operating conditions
 shuts the alternator off at wide-open throttle for better
acceleration
 accurately controls the charge rate, allowing a smaller,
lighter battery

41. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Charging
System
Internally regulated
alternator

42. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Charging
System
Note computer
monitoring, and
battery thermistor

43. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Charging System
The PCM contains the regulator circuit

44. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Fail-Safe Circuit
 Disconnects the alternator output if voltage levels
become too high
 Protects the on-board electronics

45. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
 Informs the driver of the operating condition or
output of the charging system
Types:
 warning light
 voltmeter indicator
 ammeter indicator

46. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Charging Circuit
The warning light glows when the alternator output
drops to a specified level

47. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Voltmeter Indicator
 A battery has 12.6 volts when fully charged
 Alternator output must be higher:
 13–15 volts
 A voltmeter shows the voltage

48. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Ammeter Indicator
 Shows the current output in amperes
 Reads to the right if the battery is being charged
 Reads to the left if the battery is discharging

49. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Charging Circuit
Basic connections for an
ammeter indicator