The document discusses DC generators, which convert mechanical energy into direct current electrical energy. It describes the principle of operation based on Faraday's laws of induction. The key components of a DC generator are discussed, including the yoke, poles, field winding, armature, split ring commutator, and brushes. The document explains how the commutator and brushes work together to convert the alternating current produced in the armature coils into a unidirectional direct current output. Different types of DC generators are also covered, such as separately excited, self-excited, shunt, series and compound generators.

1. Marine Electrical Practice
DC GENERATOR
GROUP 1
Name: 1. Muhamad Elfah Rizal B. Zulkarnaini
2. Mohd Zulhilmi B. Rahadi
3. Mohd Syafiq B. Sobri
Class : WKE O5
Instructor : Pn. Nurul Nazifah

2. CONTENT
NO TOPIC NAME
1 INTRODUCTION
2 PRINCIPLE OF OPERATION
3 DC GENERATOR
4 CONSTRUCTION & WORKING
5 TYPES & APPLICATION
6 REFERENCE

3. INTRODUCTION
 ELECTRIC GENERATOR is the device which converts the mechanical
energy into electrical energy.
 There are 2 type of electric generator :
1. AC generator - Produce alternating current
2. DC generator - Produce unidirectional/direct current.
 Hence the most essential part of generator are :
1. A uniform magnetic field
2. A system of conductors
3. Relative motion between the magnetic field
and conductors
 These generator produces current based on the fundamental of principle
of faraday’s law of electromagnetic induction.

4. PRINCIPLE OF OPERATION
 FARADAYS LAWS
First law : Whenever a conductor cuts magnetic flux, an e.m.f is
induced in that conductor.
Second law : The magnitude of the induced e.m.f is equal to the rate of
change of flux linkages.

5. PRINCIPLE OF OPERATION

6.  FLEMING’S RIGHT HAND RULE
- The thumb represent the direction of motion of the conductor.
- The first finger ( four finger ) represent field.
- The second finger ( middle finger ) represent current.
PRINCIPLE OF OPERATION

7. DC GENERATOR
 DC generator is an electric generator that convert alternating
current(AC) generator into unidirectional/direct current(DC) output.
 An AC current generator may be converted to DC current generator in a
couple ways :
I. By using split ring commutator instead of slip rings. The split
ring commutator is mounted on the armature shaft but is insulated
from it. The commutator revers the connection of the coil to the
external circuit each time the current reverse. Thus, DC output is
achieved from AC generator.
II. By using a bridge rectifier circuit. This is an arrangement of
electronic component (diode) that convert AC to DC.

8. DC GENERATOR

9. DC GENERATOR

11. CONSTRUCTION OF DC
GENERATOR
 DC Generator consist of a few part, which is :
1. Yoke
-Yoke is also call as frame.It provides protection to the
rotating and other parts of the machine from moisture,dust etc.
-Yoke is an iron body which provide the part for
flux and mechanical support for the pole.
2. Pole
-Carry the field winding
-Rectangle cross section
-Laminated to reduce heat losses
-Fitted to yoke through bolts
3.Field winding
-Is a set of coil
-Steady current flow through these to produce the
required magnetic field.

12. 4. Armature
- A coil wound around a metal core and mounted between the poles of an electromagnet.
5. Split Ring Commutator
- The split ring commutator is mounted on the armature shaft but is insulated from it.
- The commutator revers the connection of the coil to the external circuit each time the
current reverse.
- Use to convert AC to DC.
6. Brush
- These connect to the commutator to an external circuit and conduct the current induced in
the armature coil to external circuit.

14. WORKING OF DC GENERATOR

15.  It's seen that in the first half of the revolution current flow always along ABLMCD i.e brush no.1
in contact with segment “a” .
 In the next half revolution, in the figure the direction of the induced current in the coil is reverse
but at the same time the position of the segment “a” & “b” are also reversed which result that
brush no.1 comes intouch with the segment “b”
 The current in the load resistance again flow L to M. The wave from of the current through the
load circuit is as show in the figure.
 This current is unidirectional.
 This is basic working principal of DC generator, explained by single loop generator model.
 The position of the brush of DC generator is so arrange the change over of the segment “a”
and “b” from one brush to other takes place when the plan of rotating coil is at right angle to
the plane of line of force.
 It's so become in that position, the induced E.M.F in coil is zero.

16. TYPES OF DC GENERATOR.

17. ACCORDING TO THE WAY OF FIELD EXCITATION
1. Saparately Excited DC Generator
– The field winding is excited from dedicated DC supply
i.e : Battery
2. Self Excited DC Generator
- The field winding is excited from the armature.
No need separate DC supply.
ACCORDING TO THE CONNECTION OF FIELD WINDING
WITH RESPECT TO ARMATURE WINDING
1. Shunt Generator
- The field winding is connected in parallel with
armature winding
- Application : Lighning load, Battery charging,
Use for giving excitation to the
alternator

18. 2. Series Generator
- Field winding is connected in series with the armature.
- Application : For arc lamp, As constant current generator,
As booster on DC generator
3. Compound Generator
- Both series and shunt winding are used to get combined
characteristic of two types of generator.
- Application : Use for driving a motor, for small
distance operation (power supply for
hotel, office & home)
- Short Shunt : Only shunt field winding is in parallel with armature winding.
- Long Shunt : Shunt field winding is in parallel with both series field & armature winding.

19. REFERENCE
• https://www.slideshare.net/GaMeBoyisCool/dc-generator-67113211
• https://www.slideshare.net/jitendrakumarp2011/generatorpps?next_slidesho
w=1
• https://www.slideshare.net/GaMeBoyisCooL/dc-generator-67113211
• https://www.google.com/search?q=dc+generator+working+principle+and+
construction&ie=utf-8&oe=utf-8&client=firefox-
b#q=separately+excited+dc+generator+applications

20. THANK YOU