The document summarizes automotive charging systems and generators. It discusses how generators work using electromagnetic induction to convert mechanical energy into electrical power. It describes the key components and working of DC generators and AC alternators. Generators provide power in three stages - starting, normal operation, and peak operation. DC generators produce direct current using commutators, while alternators produce alternating current that is rectified to direct current using diodes. Key components include the rotor, stator, rectifier, and voltage regulator, which maintains a constant output voltage. Alternators have replaced DC generators in modern vehicles due to their ability to provide more power and charge the battery while idling.

1. Automotive Electrical and
Electronics
Charging Systems
By
Mr. P. Karthik selvan, AP
K L N College of Engineering

2. GENERATOR

3. Introduction
• A generator is a device that converts motive
power (mechanical energy) into electrical power for use
in an external circuit. Sources of mechanical energy
include steam turbines, gas turbines, water
turbines, internal combustion engines and even
hand cranks.
• Generators can be DC(Dynamo) and AC (Alternator)
• Generators provide nearly all of the power for electric
power grids.

4. • All charging circuits operate in three stages:
• During starting, battery supplies all load current
• During normal operation, generator supplies all current
and recharges the battery
• During peak operations, battery helps generator to
supply current
An AC Generator produce AC Power and DC Generator
produces Direct power
Both of these generators produce electrical power, based on
same fundamental principle of Faradays`s law of
electromagnetic induction.

5. • Generator works based on :
1. Faradays law of Induction
2. Flemings right hand rule
• Faraday's law of induction is a basic law
of electromagnetism predicting how a magnetic field will
interact with an electric circuit to produce an electromotive
force (EMF)—a phenomenon called electromagnetic
induction. It is the fundamental operating principle
of transformers, inductors, and many types
of electrical motors, generators and solenoids.

7. DC Generator
• A generator which produces direct current is called as a
dynamo. In the past the dynamo was the only convenient way
to generate electrical energy
Principle and Working:
If a conductor cuts magnetic lines of force,
electromagnetic force is generated in the conductor, and that
the electromagnetic force produced will vary with the number
of magnetic lines of force, number of conductors (number of
coil windings), and the speed at which the conductor cuts the
lines of magnetic. Produced current is collected by using
external circuit

8. If a conductor is turned clockwise between the N and S poles of a
magnet, electromotive force will be generated in the arrow
direction in accordance with Flemings right hand rule

9. Construction
• The generator is comprised of the poles cores, filed coils, armature ,
brushes , pulley and frame.
Pole cores- Poles cores become the N and S poles of magnet when the current
flow through field coils. Most of generator have four poles
Field coils- It is insulates wire wound in coil form and installed around the
pole core. The current flows through the field coils
Armature- It is a shaft rotates inside the pole cores and produce the
electromotive force. It is comprised of a rotating shaft with the armature
coil at the centre and the commutator at one end. The commutator serves to
convert the AC to DC
Brushes- The brushes contact against the commutator and serve to pass the
current generated in the armature to the field coil and to the outside of the
generator
It is made up on carbon
Pulley- It is provided with a fan to cool the generator

10. DC Generator Characteristics
• Electromagnetic force generated by the generator grows larger
with greater amount of flux
• For these reasons, continued high speed operation will cause
large current to flow through the battery, generator and other
circuits and shorten their service life
• On the other hand , during low speed only small current will
flow
• To prevent such condition, a regulator is provided

11. Control unit
Regulator:
It consists of three relays :
1. Voltage regulator to control the generated
voltage
2. A current limiter to control the output current
3. A cut-out relay to prevent reverse flow of
current from the battery

13. Voltage regulator:
• The purpose of this relay is to maintain the generated voltage at a
constant value.
• When the voltage rises, resistance is inserted in series with the
filed coil circuit to limit current flow through the field coils and
lower the generated voltage.
• When the voltage drops, resistance is removed from the field coil
circuit to allow the generated voltage to build up again
• The repetition of this action maintains the voltage at a constant
value.
• Classified in to – Contact point type and carbon pile type

14. Contact point type
• When the voltage rises too high, the magnetization by the
voltage coil attracts the iron piece to open the contact points.
As a result, the current flow to the field coil is limited
• When the voltage drops too low, the contact points are closed
by the tension of regulating spring to allow the voltage to
recover
• This repeated opening and closing of the contact point
maintains constant voltage

16. Current regulator
• The purpose of current regulator or limiter is to prevent
excessive current from the generator
• Its construction and operation is very similar to those of
voltage regulator
• When current rises the contact point closed, when current
become less the contact point will open

18. Cut-out rely
• A voltage regulator has an additional component known as a
cut-out relay, which prevents the battery from discharging
back into generators field after key turned OFF or engine
idling
• Without cut-out relay the generator would always in ON and
lead to drain battery even without engine running
• When generator speed drops – Generating voltage becomes
lower than battery voltage
• Cut-out relay – one form of Automatic switch

20. Construction
• When the generator is not working, contact points are held
open , after generator starts coils get magnetized so that
contact points are attracted and close
• Based on generator speed, closing and opening of contact
points will be achieved
• The charging circuit is used to prevent the reverse flow of
current

21. ALTERNATOR

22. Introduction
• The increasing numbers of accessories also consume a large
amount of power we need to generate more power.
• But DC Generator capacity is only limited to over come this
problem Alternator is used
• Alternator is the heart of the vehicles electrical system when
the engine is running. It uses electromagnetism to change
some of the engines mechanical energy into electrical energy
• Two types alternators – Conventional and separate voltage
regulator type
• In recent, In built regulator alternator is used
• Amps rating- 40 to 80 amps

23. Construction
• The alternator is comprised primarily of the stator, rotor,
bracket, rectifier(silicon diodes) and brushes.
Stator- It has three sets of armature coils wound on it to induce a
three phase current.
Rotor- Rotors can be classified into the salient pole type and
Randell type. At present randell is mostly used. In this type the
number of poles is equal to the numbers of finers
Bracket- The end bracket opposite to the pulley side has six
diodes assembled into it that serve to rectify all of the three
phase AC generated
Brushes - It serves to pass a current of 2 to 3 amperes to the
rotor coils. In alternator the main current does not flow
through these brushes

24. • Rectifier- Alternator produce three phase AC but the
automobile charging system need DC supply. Converting AC
to DC is called rectification. Rectification can be done in
several ways but efficient way is using diode

25. Working
• An alternator is designed to change mechanical energy into
electrical energy
• The working principle of an alternator is an electromagnetic
induction (EMI)
• When the rotor spins, its strong magnetic filed cuts across the stator
windings. This induces current in the stator windings
• If the stator winding are connected to a load(Ex- bulb), the load
would operate
• Slip rings are used

27. • Advantage:
• Rotor has high strength against speed
• Good rectifying characteristics
• Current limiter not required depending on the design
• Cut-out relay not required
• Charging is possible while idling