Topic

DC GENERATOR’S

by

NOMAN AHMED RAJPUT

CONTENT’S

Introduction of DC GeneratorPrinciple of DC GeneratorTypes of Generator’sFaraday’s LawClassification’s of Generator’s

Separately Excited DC Generator’s

Self Excited DC Generator’s

The device which converts mechanical energy to electrical energy is called generator

1.Introduction to Generators

GENERATOR ELECTRICAL ENERGYMEHANICAL ENERG Y

Principle

Types Of

Generator’s

There are two types of generators, one is ac generator and other is dc generator.

Whatever may be the types of generators, it always converts mechanical power to electrical power.

An ac generator produces alternating power. A dc generator produces direct power.

Both of these generators produce electrical power, based on same fundamental principle of Faraday's law of electromagnetic induction

AC

DC

PART’S OF FARADAY’S LAW

EMF PRODUCE DYNAMICALLY

EMF PRODUCE STATICALLY

1ST PART

2ND PART

DynamicallyEMF Induced if flux remain constant and conductor move and hence cut’s

the magnetic field

StaticallyIf set of stationary conductor’s placed in time Varying magnetic field then EMF will produce statically

Classifications of generator’s

According to out put Generator’s can beclassified as

According to mechanical work input generatorcan also be classified as:

1) AC Generator’s 1) DC Generator’s

1) Engine Generator 2)Human Powered

3) Turbine Generator’s4) Wind Powered

Classification According to Excitation

Separately Excited DC GeneratorSelf Excited DC

GeneratorSELF EXCITED

SERIES

WOUND SHUNT WOUND

COMPOUND WOUND

Separately Excited Separately excited generators are those whose whose field magnets are energized from external source of dc current

Diagram

Self Excited DC Generator

These are generators in which the field winding is excited by the output of the generator itself.there are three types of self excited dc generators.

1) Series Wound

2) Shunt Wound

3) Compound Wound

Series woundIn these type of generators, the field windings are connected in series with armature conductors

whole electric current flows through the field coils as well as the load.

As series field winding carries full load current it is designed with relatively few turns of thick wire.

The electrical resistance of series field winding is therefore very low (nearly 0.5Ω ).

SERIES WOUND

Shunt WoundIn these type of DC generators the field windings are connected in parallel with armature conductorsIn shunt wound generators the voltage in the field winding is same as the voltage across the terminal.

The field winding has high resistance and more number of turns so that only a part of armature current passes through field winding and the rest passes through load.

Shunt wound

Compound WoundIn series wound generators, the output voltage is directly proportional with load current.In shunt wound generators, output voltage is inversely proportional with load current.A combination of these two types of generators can overcome the disadvantages of both. This combination of windings is called compound wound DC generator.A compound wound further divided into two types

Compound Wound

Short ShuntLong Shunt

Short Shunt

THE GENERATORS IN WHICH ONLY SHUNT FIELD WINDING IS IN PARALLEL WITH THE ARMATURE WINDING

LONG SHUNT The generators in which shunt field winding is in parallel with both series field and armature winding