This document discusses generators and their components. It describes the key parts of DC generators including the yoke, poles, field winding, armature, commutator, and brushes. It explains how DC generators work using electromagnetic induction to convert mechanical energy into electrical energy. Characteristics of DC generators like open circuit characteristics, internal characteristics, and external characteristics are also summarized.

1. UNIT II
CHARGING SYSTEM LIGHTING AND
ACCESSORIES
DC Generators and Alternators their characteristics.
Control unit – cut out, electronic regulators. Vehicle
interior lighting system. Vehicle exterior lighting system.
Wiring requirements. Lighting design. Dashboard
instruments. Horn, trafficator.

2. INTRODUCTION
• The Device which Converts the Mechanical Energy into
Electrical Energy is called Generator.
• There are Two types of Generators
1. D.C Generator:- The Generator which converts the
Mechanical Energy into D.C Form of Electrical Energy is
called D.C Generator.
2. A.C Generator:- The Generator which converts the
Mechanical Energy into A.C Form of Electrical Energy is called
A.C Generator.
• Both of the Generator Works on the Principle of Faraday’s Law
of Electromagnetic Induction.

3. PRINCIPLE OF OPERATION
• In 1831, Michael Faraday, an English physicist gave one of the most
basic laws of electromagnetism called Faraday's law of
electromagnetic induction.

8. CONSTRUCTION
• Important Parts of D.C Generator
1. YOKE
2. POLES
3. FIELD WINDING
4. ARMATURE
5. COMMUTATOR,BRUSHES and GEAR
6. BEARINGS

11. DC GENERATOR

15. YOKE
• Yoke is also called as frame. It provides protection to the rotating and
other parts of the machine from moisture, dust etc.
• Yoke is an iron body which provides the path for flux
• It provides the mechanical support for the poles.
• Materials used for yoke are cast iron, silicon steel, cast steel, rolled
steel etc.

16. POLE
• Pole produce the magnetic flux when the field winding is excited.
• Materials used for Pole is cast steel or cast iron.
• Pole is a Part on Which Field Winding is Wound Over.

18. FIELD WINDING
• The field winding is also called as exciting winding.
• Current is passed through the field winding in a specific direction ,to
magnetize the pole.
• The metal is used for the field conductor is copper.

19. ARMATURE CORE
• All these slots are parallel to the shaft axis.
•Armature conductor are placed in these slots.
•Armature core provides a low reluctance path to the flux produced
by the field winding.
•Cast steel or cast iron are used for the armature core.

22. COMMUTATOR
• The commutator converts the alternating emf generated internally in
a D.C.voltage .
• It collects the current from the armature conductors and passes it to
the external load via brush.

23. ROTOR
• The Rotor is the moving part of a D.C. generator.
• The rotor rotates because the wires and magnetic field of the
motor are arranged so that a torque is developed about the rotor’s
axis.

24. WORKING of DC GENERATOR

25. • The Dc Generator Converts Mechanical Energy into Electrical
Energy.
• In this DC Generator the Single Turn Alternator is used.
• The Coil can Rotate in Clockwise or Anticlockwise Direction.
• The Commutator Brush is Connected to the Coil.
• Commutator is Divided into Two Parts A and B.
• The Coil is Suspended between the Field Poles.
• The Coil is Given the Mechanical Energy which Results in the
Rotation of it.

26. • As the Commutator Segments A&B is Connected with Conducting
Coil ab and cd Respectively they Rotate Together.
• Due to Which the Flux is Produced Resulting in the Generation of
Electric Current.
• As the Commutator has the Property of Converting the
Bidirectional Emf(AC) into Unidirectional Emf (DC) .
• The DC Current is Generated by the DC Generator.
• Which can Directly Used by Connecting the Output across the
Load or it Can be stored inatteries and Can be used Later on.

27. GENERATION OF AC VOLTAGE
• As Shown in Fig the Coil is in Rotating Form.
• The EMF is Generated by Rotation of Coil.
• In this Fig A,B,C and D is used to Describe the Position of the Coil.
• When the Coil is stationary the EMF Generated is Null.
• When the Coil Rotates at 90 Degree as Shown in Fig B.The Flux is
Generated resulting in the AC Voltage at Output.

28. • When the Coil Reaches at C the Half Cycle of the Rotation is
Complete.
• When the Coil Rotates Further another Half Cycle of Sine wave is
Generated.
• The Efficiency of the DC Generator can be Increased by Combining
Two or More Number of Coils at Same Time.
• Which Will Result in Attaining 360 Degrees at only One Rotation
of the Coil

31. CLASSIFICATION

32. APPLICATIONS
• Shunt generator:
Lighting loads Battery charging
• Series generator:
For the arc lamps As constant current generator As boosters on D.C.
generator
Separately Exicted generator:
The application of these generator have limitations , because they
need a separate excitation for the field winding. Some of the
application are electro-refining of materials or electro-plating.

33. • Cumulative compound generator:
Used for domestic lighting For energy transmission over a long
distance.
• Differential compound generator:
• Its important application is electric arc welding

39. Characteristics of DC generators
The speed of a d.c. machine operated as a generator is fixed by the
prime mover. For general-purpose operation, the prime mover is
equipped with a speed governor so that the speed of the generator is
practically constant. Under such condition, the generator
performance deals primarily with the relation between excitation,
terminal voltage and load.

40. These relations can be best exhibited graphically by means of
curves known as generator characteristics. These characteristics
show at a glance the behaviour of the generator under different
load conditions.
D.C. Generator Characteristics The following are the three most
important characteristics of a d.c. generator:

41. 1. Open Circuit Characteristic (O.C.C.):
This curve shows the relation between the generated e.m.f. at no-
load (E0) and the field current (If) at constant speed.
It is also known as magnetic characteristic or no-load saturation
curve.
Its shape is practically the same for all generators whether
separately or self-excited. The data for O.C.C. curve are obtained
experimentally by operating the generator at no load and constant
speed and recording the change in terminal voltage as the field
current is varied.

42. 2. Internal or Total characteristic (E/Ia)
This curve shows the relation between the generated e.m.f. on load
(E) and the armature current (Ia).
The e.m.f. E is less than E0 due to the demagnetizing effect of
armature reaction.
Therefore, this curve will lie below the open circuit characteristic
(O.C.C.). The internal characteristic is of interest chiefly to the
designer.

43. It cannot be obtained directly by experiment. It is because a
voltmeter cannot read the e.m.f. generated on load due to the
voltage drop in armature resistance.
The internal characteristic can be obtained from external
characteristic if winding resistances are known because armature
reaction effect is included in both characteristics.

44. 3. External characteristic (V/IL):
This curve shows the relation between the terminal voltage (V) and
load current (IL).
The terminal voltage V will be less than E due to voltage drop in the
armature circuit.
Therefore, this curve will lie below the internal characteristic.
This characteristic is very important in determining the suitability of
a generator for a given purpose.
It can be obtained by making simultaneous measurements of
terminal voltage and load current (with voltmeter and ammeter) of a
loaded generator.

45. Definition of Stator
The stator is the static part of the motor. The main function of the
stator is to generate the rotating magnetic field. The stator frame,
stator core and stator winding are the three parts of the stator. The
stator core support and protect the three-phase winding of the stator.
High-grade silicon steel stamping makes the core of the stator.

46. Definition of Rotor
The rotating part of the motor is known as the rotor. The rotor core and
the rotor winding are the part of the rotor. The winding of the rotor is
excited by the DC supply. The squirrel cage and the phase wound are
the types of the rotor.

47. The core of the squirrel cage rotor is made of the cylindrical iron
core.
The core has a semi-circular slot on their outer surface on which
the copper or aluminium conductors are placed.
The conductors are short-circuited at the ends with the help of the
aluminium or copper rings.

48. Working of Rotor & Stator
The stator generates the rotating magnetic field because of the three-
phase supply.
If the rotor is in the standstill condition, then the electromagnetic
force induces in them because of the electromagnetic induction
phenomena.
The electromagnetic induction is the phenomena in which the emf
induced in the current carrying conductor because of the variable
magnetic field.
The current induces in the rotor which causes the rotor to move.

49. Key Differences Between Stator and Rotor
The stator is the stationary part of the machine, whereas the rotor is
the movable part of the machine.
The stator core, stator winding and the outer frame are the three
parts of the stator whereas the rotor core and field winding are the
parts of the rotor.
The three-phase supply is given to the winding of the stator. The
rotor is excited by the DC supply.

50. The winding arrangement of the stator is more complex as compared
to the rotor.
The stator winding is highly insulated because high voltage induces
in it. Whereas, the rotor has low insulation.
The size of the stator winding is large for carrying the heavy current
as compared to the field winding.
The cooling system of the stator is good as compared to the rotor
Because the stator is stationary.
The friction loss is less in the rotor as compared to the stator because
of its low weight.