Transformer Fully Explained by Faisal Qaswar Shahbaz

8/8/2019 Transformer Fully Explained by Faisal Qaswar Shahbaz

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PRESENTATION ON

ELECTROMEGNATISM

Presented to:

Prof Dr. Tariq Bhatti

Presented by:MUHAMMAD FAISAL RAO

Roll No:07-49

BS(IT) 3rd

Dept. of Computer ScienceBahauddin zakariyauniversity, Multan


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Transformer


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Transformer

A transformer is a

device that

transfers electrical

energy from onecircuit to another

through inductively

coupled electrical

conductors


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Transformer

A transformer is a device thattransfers electrical energy from

one circuit to another through

inductively coupled electrical

conductors.

A changing current in the first

circuit (the primary) creates a

changing magnetic field.


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This changing magnetic field

induces a changing voltage in the

second circuit (the secondary).This effect is called mutual

induction.


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If a load is connected to thesecondary circuit, electric charge

will flow in the secondary windingof the transformer and transferenergy from the primary circuit tothe load connected in the

secondary circuit


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The secondary induced voltage VS, of

an ideal transformer, is scaled from

the primary VPby a factor equal to

the ratio of the number of turns of

wire in their respective windings:


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By appropriate selection of

the numbers of turns, a

transformer thus allows analternating voltage to be

stepped up by making NS

more than NP or stepped

down, by making it less.


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Transformers are some of the mostefficient electrical 'machines', withsome large units able to transfer

99.75% of their input power to theiroutput.

Transformers come in a range of

sizes from a thumbnail-sized couplingtransformer hidden inside a stagemicrophone to huge units weighinghundreds of tons used to interconnect

portions of national power grids.


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PRESENTATION ON

ELECTROMEGNATISM

Presented to:

Prof Dr.Tariq Bhatti

Presented by:Muhammad Qaswar

Roll No:07-27

BS(IT) 3rd



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Construction


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Laminated core

transformer

showing edge of

laminations at top

of unit.


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Laminated steel cores

Transformers for use at power or

audio frequencies typically have cores

made of high permeability silicon

steel.The steel has a permeability many

times that of free space, and the core

thus serves to greatly reduce themagnetising current, and confine the

flux to a path which closely couples

the windings.


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Early transformer developers soon

realized that cores constructed from

solid iron resulted in prohibitive eddy-

current losses, and their designs

mitigated this effect with cores

consisting of bundles of insulated iron

wires.


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Later designs constructed the core by

stacking layers of thin steel

laminations, a principle that has

remained in use.

Each lamination is insulated from its

neighbors by a thin non-conducting

layer of insulation.


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The effect of laminations is to confine

eddy currents to highly elliptical pathsthat enclose little flux, and so reduce

their magnitude.

Thinner laminations reduce losses, but

are more laborious and expensive to

construct.

Thin laminations are generally used on

high frequency transformers, with sometypes of very thin steel laminations able

to operate up to 10 kHz.


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Solid cores

Powdered iron cores are used in circuits(such as switch-mode power supplies) thatoperate above main frequencies and up toa few tens of kilohertz. These materials

combine high magnetic permeability withhigh bulk electrical resistivity.

For frequencies extending beyond theVHF band, cores made from non-conductive magnetic ceramic materialscalled ferrites are common. Some radio-frequency transformers also have movablecores (sometimes called 'slugs') whichallow adjustment of the coupling coefficient

(and bandwidth) of tuned radio-frequencycircuits.


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Windings

Windings are usually arranged concentrically to

minimize flux leakage


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Cut view through transformer windings.White: insulator. Green spiral: Grain

oriented silicon steel.Black: Primary winding made of oxygen-

free copper. Red: Secondary winding. Topleft: Toroidal transformer. Right: C-core,but E-core would be similar. The blackwindings are made of film. Top: Equally lowcapacitance between all ends of bothwindings. Since most cores are at leastmoderately conductive they also need

insulation. Bottom: Lowest capacitance forone end of the secondary winding neededfor low-power high-voltage transformers.


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Three-phase oil-

cooled transformerwith cover cut away.

The oil reservoir is

visible at the top.Radiative fins aid the

dissipation of heat.


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Terminals

Very small transformers will have wireleads connected directly to the endsof the coils, and brought out to thebase of the unit for circuitconnections.

Larger transformers may have heavybolted terminals, bus bars or high-voltage insulated bushings made ofpolymers or porcelain.

A large bushing can be a complexstructure since it must provide carefulcontrol of the electric field gradientwithout letting the transformer leak oil.


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A Presentation on

Types of TransformersPresented by:

Malik Ajmal

BS(IT)-07-12

Presented to:

Dr.Tariq Bhatti sb.


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Transformer

A transformer is a

device that

transfers electrical

energy from onecircuit to another

through inductively

coupled electrical

conductors


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Types of Transformers:

A wide variety of transformer designsare used for different applications.

Some important types are given as:

Auto-transformer

Poly-phase transormer

Leakage transformer

Resonant transformer

Instrument transformers


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AUTO-TRANSFORMERS

An autotransformer with a sliding

brush contact

An autotransformer has only a singlewinding with two end terminals, plus a

third at an intermediate tap point.


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POLY-PHASE TRANSFORMER

For three-phase supplies,a bank of

three individual single-phase

transformers can be used,or all three

phases can be incorporated as a

single three-phase transformer.


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LEAKAGE TRANSFORMERS

A leakage transformer,also called a

stray-field transformer, has a

significantly higher leakage

inductance than other transformers.


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RESONANT TRANSFORMERS

A resonant transformer is a kind of

the leakage transformer. It uses the

leakage inductance of its secondary

windings in combination with external

capacitors, to create one or more

resonant circuits.


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INSTRUMENT TRANSFORMERS

Current transformers, designed to be

looped around conductor.

A current transformer is ameasurement device designed to

provide a current in its secondary coil

proportional to the current flowing in

its primary.


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PRESENTATION ON

ELECTROMEGNATISM

Presented to:

Prof Dr. Tariq Bhatti

Presented by:

SHAHBAZ HUSSAIN

Roll No:07-26

BS(IT) 3rd



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Basic principle of Transformer:


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TRANSFORMERS

A transformer is a device that

transfers electrical energy from one

circuit to another through inductively

coupled electrical conductors.


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TRANSFORMERS RULES

Transformer is

based on two

principles:

Firstly,that anelectric current can

produce a

magnetic.

Secondly,

electromegnetic

induction


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TRANSFORMERS

By changing the

current in the primary

coil, it changes the

strength of its

magnetic field

The changing

magnetic field extends

into the secondary

coil, a voltage isinduced across the

secondary.


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Induction law

Faradays law states that:

Vs=Ns.d/dtwhere VS is the instantaneous

voltage.

NS is the number of turns in the

secondary coil.


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Since the same magnetic flux passes

through both the primary and

secondary coils in an ideal

transformer,the instantaneous voltage

across the primary coil

Vp=Np.d/dt


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Taking the ratio of the two equationsTaking the ratio of the two equations

forfor VSVSandand VPVPgives the basicgives the basic

equation for stepping up or steppingequation for stepping up or stepping

down the voltagedown the voltage


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If Ns>Np, Vs>Vp

Such transformer voltage across

secondary is greater than primaryvoltage called step up transformer.

Voltage cross secondary less than

primary voltage called step down

transformer.


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Ideal power equation

Power input=power outputVpIp=VsIs

Vs/Vp=Ip/Is

Where current is inversaly

proportional to respective voltage.


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Step up Vs Voltage increase then

secondary current reduced.

When current passes throughresistance then power loss due to

heating effect.


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THANKS!!!


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Transformer Fully Explained by Faisal Qaswar Shahbaz

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