1. Presented By Abu Syed Md. Jannatul Islam Lecturer, Dept. of EEE
DC GENERATOR
Presented By
Abu Syed Md. Jannatul Islam
Lecturer, Dept. of EEE
Khulna University of Engineering & Technology

2. Classification of Electrical Machines
DC Machines
AC Machines

3. DC Machines
DC Machines
DC Generator
DC Motor

4. DC MACHINES
DC GENERATOR
SEPERATELY EXCITED
SELF EXCITED
SHUNT
SERIES
COMPOUND
CUMULATIVE
DIFFERENTIAL
DC MOTOR

5. OUTLINE Principle of Operation of DC Generator
Different Parts of a DC Generator and their Functions

6. GENERATOR
A Generator is a Machine that converts Mechanical energy into Electrical energy.

7. DC Generator
A DC generator is an Electrical Machine which converts Mechanical energy into Electrical Energy (DC).
The Energy conversion is based on Faraday’s Law of Electromagnetic Induction.

8. Faraday’s Law of Electromagnetic Induction
According to this law, when an conductor moves in a magnetic field it cuts magnetic lines of force, due to which an emf is induced in the conductor.
The magnitude of this induced emf depends upon the rate of change of flux (magnetic line force) linkage with the conductor.
This emf will cause an current to flow if the conductor circuit is closed.

9. Basic Parts of a Generator
The two basic essential parts of an generator are 1) a Magnetic Field and 2) Conductors which move inside that Magnetic Field.

10. Fleming's Right-hand Rule
Fleming's Right-hand Rule (for generators) shows the direction of induced current when a conductor attached to a circuit moves in a magnetic field. It can be used to determine the direction of current in a generator's windings.

11. Fleming's Right-hand Rule and Direction of Current

12. Fleming's Right-hand Rule and Direction of Current

13. Principle of Operation of DC Generator
Whenever a conductor is moved within a magnetic field in such a way that the conductor cuts across magnetic lines of flux, voltage is generated in the conductor.
The AMOUNT of voltage generated depends on:
the strength of the magnetic field,
the angle at which the conductor cuts the magnetic field,
the speed at which the conductor is moved, and
the length of the conductor within the magnetic field

14. Principle of Operation of
DC Generator
An elementary generator consists of a wire loop mounted on the shaft, so that it can be rotated in a stationary magnetic field.
This will produce an induced emf in the loop.
The pole pieces (marked N and S) provide the magnetic field. The pole pieces are shaped and positioned as shown to concentrate the magnetic field as close as possible to the wire loop.

15. Principle of Operation of DC
Generator
The loop of wire that rotates through the field is called the ARMATURE. The ends of the armature loop are connected to rings called SLIP RINGS.
The brushes, usually made of carbon, with wires attached to them, ride against the rings. The generated voltage appears across these brushes. Sliding contacts or brushes connect the loop to an external circuit load in order to pick up or use the induced emf

16. Principle of Operation of
Generator

17. AC to DC Conversion

18. AC to DC Generator

19. Parts of a DC Generator

20. Parts of a DC Generator

21. Parts of a DC Generator

22. Yoke
The outer frame of a generator or motor is called as yoke. Yoke is made up of cast iron or steel.
Yoke provides mechanical strength for whole assembly of the generator (or motor).
It also carries the magnetic flux produced by the poles.

23. Armature Core Armature core is the rotor of a generator.
Armature core is cylindrical in shape on which slots are provided to carry armature windings.

24. Poles and Pole Shoe
Poles are joined to the yoke with the help of screws or welding.
Poles are to support field windings. 
Field winding is wound on poles and connected in series or parallel with armature winding or sometimes separately.
Pole shoe is an extended part of the pole which serves two purposes,
(1) to prevent field coils from slipping and
(2) to spread out the flux in air gap uniformly.

25. Pole and Pole Shoe

26. Commutator Brushes & Bearings

27. Commutator and Brushes
Conducting brushes rest on commutator and they slides over when rotor (hence commutator) rotates.
Thus brushes are physically in contact with armature conductors hence wires can be connected to brushes. 

28. Brushes & Bearings

29. Armature Winding

30. Armature Winding

31. Armature Winding

32. Armature Winding