2. CONTENTS
INTRODUCTION OF D.C MACHINE
APPLICATION OF FLEMINGS RULE IN D.C MACHINE
D.C GENERATOR
D.C MOTOR
ADVANTAGES,DISADVANTAGES,AND APPLICATION OF
D.C GENERATOR
ADVANTAGES,DISADVANTAGES AND APPLICATION OF
D.C MOTOR
3. INTRODUCTION OF D.C MACHINE
A DC Machine is an electro-mechanical energy
conversion device. There are two types of DC machines;
one is DC generator, and another one is known as DC
motor. A DC generator converts mechanical power (ωT)
into DC electrical power (EI), whereas, a DC motor
converts d.c electrical power into mechanical power.
4. Generator action:
An emf (voltage) is induced in a conductor if it moves
through a magnetic field.
5. Motor action: A force is induced in a conductor
that has a current going through it and placed in a
magnetic field
6. APPLICATION OF FLEMINGS RULE IN D.C
MACHINE
FLEMINGS RIGHT HAND RULE:
Used to determine the direction of emf induced
in a conductor
The middle finger , the fore finger and thumb of
the left hand are kept at right angles to one
another.
The fore finger represent the
direction of magnetic field
The thumb represent the direction of
motion of the conductor
The middle finger will indicate the
direction of the inducted emf .
This rule is used in DC Generators
Len’s LaW
7. FLEMINGS LEFT HAND RULE:
Used to determine the direction of force acting
on a current carrying conductor placed in a
magnetic field .
The middle finger , the fore finger and thumb of
the left hand are kept at right angles to one
another .
The middle finger represent the direction
of current
The fore finger represent the direction of
magnetic field
The thumb will indicate the direction of
force acting on the conductor .
This rule is used in motors.
8. D.C GENRATOR
Mechanical energy is converted to
electrical energy
Three requirements are essential
1. Conductors
2. Magnetic field
3. Mechanical energy
Working principle
A generator works on the principles of
Faraday’s law of electromagnetic
induction
Whenever a conductor is moved in the
magnetic field , an emf is induced and
the magnitude of the induced emf is
directly proportional to the rate of change
of flux linkage.
This emf causes a current flow if the
conductor circuit is closed
9. CONSTRUCTION OF D.C GENERATOR
Construction of DC
Generator
Field system
Armature core
Armature
winding
Commutator
Brushes
10. TYPES OF D.C GENERATOR
DC generators are generally classified according to their
method of excitation .
Separately excited DC generator
Self excited D C generator
Further classification of DC Generator
Series wound generator
Shunt wound generator
Compound wound generator
Short shunt & Long shunt
Cumulatively compound
&
Differentially compound
11. D.C MOTOR
Converts Electrical energy into Mechanical energy
Construction : Same for Generator and motor
Working principle : Whenever a current carrying
conductor is placed in the magnetic field , a force is set
up on the conductor.
Back emf
The induced emf in the rotating armature
conductors always acts in the opposite
direction of the supply voltage .
According to the Lenz’s law, the direction
of the induced emf is always so as to
oppose the cause producing it .
In a DC motor , the supply voltage is the
cause and hence this induced emf
opposes the supply voltage
12. Classification of DC motors
DC motors are mainly classified into three types as listed
below:
Shunt motor
Series motor
Compound motor
Differential compound
Cumulative compound
13. Advantages of D.C Generator:
Advantages of the DC generators are very few like ease of parallel operation, simple
design and construction and lesser system stability issues unlike the alternators.
Disadvantages of DC Generators:
DC generators require a split ring commutator which complicates the design.
Higher cost
A higher level of maintenance
During the generation of energy, sparks are generated
Lose more energy during transmission
APPLICATION OF D.C GENERATOR
They are used for general lighting.
They are used to charge battery because they can be made to give constant
output voltage.
They are used for giving the excitation to the alternators.
They are also used for small power supply (such as a portable generator).
14. ADVANTAGES OD D.C MOTOR :
.Speed control over a wide range both above and below the rated speed
.Higher starting torque,
.Quick starting and stopping,
.Reversing, variable speeds with voltage input and they are easier and cheaper to
control than AC.
DISADVANTAGES OF D.C MOTOR
.High initial cost
..Increased operation and maintenance cost due to presence of commutator and
brush gear
.Cannot operate in explosive and hazard conditions due to sparking occur at brush (
risk in commutation failure)
APPLICATION OF D.C MOTOR
Electric traction
Cranes
Elevators
Air compressor
Vacuum cleaner
Hair drier
Sewing machineD
15. CONCLUSION:
The electric motor has changed the framework of human society.
Electric motors are important in a lot of of objects society use everyday such as fans, fridges, and
washing machines.
New jobs are also being made in manufacturing, repair technician, and new inventions and research.
Society could never be the same without electric motors. Skyscrapers could never be built with
mechanical cranes, robots could exist, and life could not be the same without all the inventions that
use electric motors.
