4 generator working.pdf

8/14/2019 4 generator working.pdf

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GENERATION OF

ELECTRICITY

MR. SUDHIRCHOPADE


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Index Types of electrical machines

Principles on which electrical machines work

How electricity is generated

What are the important parts of basic generator

What are the parts of actual generator

What are the differences in ac and DC generator What are the additional auxiliaries required for large size

generator and why

Construction of large size generator in detail


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Basic principles

Electric machines can be broadly classified into electrostatic

machines and electro-magnetic machines.

The electrostatic principles do not yield practical machines forcommercial electric power generation.

-

principles.

Though one sees a variety of electrical machines in the market,

the basic under-lying principles of all these are the same.

To understand, design and use these machines the

following laws must be studied.


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2)Faradays laws of electromagnetic induction

Faraday proposed these laws of Induction in 1831, It

states that if the magnetic flux lines linking a closed

electric coil changes, then an emf is induced in the

coil.

: s em s propor ona o e ra e ochange of these flux linkages.

This can be expressed mathematically,

Here N is the number of turns of the coil, and is the flux

lines in weber.


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ii) Second law

The direction of the induced emf can be determined

by the application of Lenz's law.

Lenz's law states that the direction of the induced emf

is such as to produce an effect to oppose this change

in flux linkages.

e=-N(d/dt)

It is analogous to the inertia in the mechanical

systems.


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3) Flemings left and right hand rules Flemings left hand

and right hand rulesgive relation between

Magnetic field, EMF

Left hand rule is for

direction of motionof motor & Right

hand rule gives

an mot on. rect on o n uceEMF


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i)Flemings Left Hand Rule( for the direction of rotation of motors)

This rule is also called Fleming'sLeft Hand Rule, after Englishelectronics pioneerJohn Ambrose

Fleming First finger represents the direction

of theField.

The Second finger represents the

[conventional current, positive(+) tonegative(-).

The Thumb represents the directionof the Thrust or resultantMotion.

FBI - moving from thumb to secondfinger.

The thumb is the force F

The first finger is the magnetic fieldB

The second finger is the of current I


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ii)Fleming's right hand rule for direction of induced

EMF in Generator.

point your thumb in thedirection of the current andlet your fingers assume a

curved position, themagnetic field circlingaround the wires flows in thedirection in which your four

ngers po n .

Fleming's right hand rule(for generators). Theappropriately-handed rule

can be recalled byremembering that the letter"g" is in "right" and"generator"


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4) Corkscrew Rule :

It simply shows how

a current-carryingwire generates a

.


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Index

What is electricity

Working principle of generator

Basic laws

Working of small generators

Parts of small generators

Parts of large generators


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What is Electric Current

The movement of charges such as electrons is called

current, and this electrical current is what powershousehold appliances.

arge ass ng roug ven rea

current = -------------------------------Time


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Electricity by definition is electric current that is usedas a power source!

This electric current is generated in a power plant,

and then sent out over a power grid to your homes,and ultimately to your power outlets.


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What is generator?

Electrical generator is a machine which convertmechanical energy into electricity.

to faradays law of electromagnetic inductiondynamically induced emf is produced in it.

This emf causes a current to circulate through thewinding if close path.


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Prerequisites for generation of electricityTwo important things required for generation of electricity

1)Magnetic field2)Moving conductor to cut magnetic field


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Simple formulae for generation of electricity

(faradays law)


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Application of formula


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Simple electric generator


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BASIC GENERATOR


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MAIN COMPONENTS OF GENERATOR


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Important Parts of generator1) Magnetic frame or yoke

2) Pole shoes and pole coils

3) Armature core and winding

4) Commutator and brushes5) Bearing


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Parts of D. c. generator


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COMMUTATOR


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Parts of generator


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Laminated

pole

structure

and

armaturecore


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Mounting of armature winding in slots


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Commutator and its parts


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Brushes and bearings


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Mountings of brushes on commutator


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Parts of turbo generator


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Constructional differences betweenSmall and large generator

1)Location of field winding2) Commutator limitations

oo ng pro ems 4)No of poles


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GENERATOR ASSEMBLY


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CONSTRUCTION OF STATOR FRAMECONSTRUCTION OF STATOR FRAMECONSTRUCTION OF STATOR FRAMECONSTRUCTION OF STATOR FRAME

The stator frame is gas tight fabricated structure

It comprises of inner and outer frame

The inner frame is made up by circular and axial steel ribs

fixed inside the outer frame.


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STATOR FRAME


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STATOR CAGE


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STATOR CORESTATOR CORESTATOR CORESTATOR CORE

The stator core is made of laminations

It is made up from large number of varnish insulated punching

or section of thin (0.35 to 0.5mm ) steel sheets

The sheets are tightly pressed to form a monolithic structure

Some spacers are provided for hydrogen circulation


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STATOR CORE

STATOR CORE BUILDING IN PROGRESS


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STATOR CORE BUILDING IN PROGRESS

STATOR CORE ASSEMBLY


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STATOR CORE ASSEMBLY


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STATOR CONDUCTOR

UU


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STATOR CONDUCTORSSTATOR CONDUCTORSSTATOR CONDUCTORSSTATOR CONDUCTORS

The stator winding is placed in stator core slots

The voltage and current level is 15.75kv & 9050 amp for210mw unit

Therefore the conductor and insulation must be capable ofwithstanding the current and voltage without overheating and

leakage.

The stator winding is three phase double layer, short chorded,

and transposed along the length of slot


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STATOR CONDUCTORS CONTDSTATOR CONDUCTORS CONTDSTATOR CONDUCTORS CONTDSTATOR CONDUCTORS CONTD


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STATOR CONDUCTORS CONTDSTATOR CONDUCTORS CONTDSTATOR CONDUCTORS CONTDSTATOR CONDUCTORS CONTD-

Each coil consists of solid and hollow conductors to provide path

for cooling water

The hollow conductors are connected to cooling water supply viaa Teflon tube.

The stator winding is made from copper strips with insulatedtape impregnated with varnish, dried under vacuum and hot

pressed to form solid insulated bar

The bars are placed in core slots and held in position with

insulating material wedges


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COMPLETE STATOR


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COMPLETE STATOR


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ROTOR WINDING AND COMPLETE

ROTOR


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LAMINATED ROTOR


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COMPLETE ROTOR ASSEMBLY


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C R R ASS

BRUSHGEAR


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R G AR


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Brush gear

DC supply (310v,2600a)is given to rotor winding through two

alloy steel slip rings and spring loaded carbon brushes mounted

on extended portion of rotor shaft at free end

and are insulated from rotor shaft

Excitation supply is connected to brushgear assembly through

cables


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Generator bearingGenerator bearingGenerator bearingGenerator bearing

Generator bearing are pedestal type white metal bearing

with spherical sealing to allow self alignment

These bearings are self lubricated


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GENERATOR EXCITER


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GENERATOR ASSEMBLY


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