Electrical Transformer - Basic Construction, Working and Types _ Electricaleasy

3/23/2015 ElectricalTransformerBasicconstruction,workingandtypes|electricaleasy.com

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ElectricalTransformer -BasicConstruction,Working AndTypes

Electrical transformer is a staticelectrical machine which transformselectrical power from one circuit toanother circuit, without changing thefrequency. Transformer can increaseor decrease the voltage withcorresponding decrease or increase incurrent.

Working Principle OfTransformer

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The basic principle behind workingof a transformer is the phenomenonof mutual induction between twowindings linked by common magneticflux. The figure at right shows thesimplest form of a transformer.Basically a transformer consists of twoinductive coils; primary winding andsecondary winding. The coils areelectrically separated but magneticallylinked to each other. When, primarywinding is connected to a source ofalternating voltage, alternatingmagnetic flux is produced around thewinding. The core provides magneticpath for the flux, to get linked with thesecondary winding. Most of the fluxgets linked with the secondary windingwhich is called as 'useful flux' or main'flux', and the flux which does not getlinked with secondary winding is calledas 'leakage flux'. As the flux producedis alternating (the direction of it iscontinuously changing), EMF getsinduced in the secondary windingaccording to Faraday's law ofelectromagnetic induction. This emf iscalled 'mutually induced emf', and thefrequency of mutually induced emf issame as that of supplied emf. If thesecondary winding is closed circuit,then mutually induced current flowsthrough it, and hence the electricalenergy is transferred from one circuit



(primary) to another circuit(secondary).

Basic Construction OfTransformer

Basically a transformer consists of twoinductive windings and a laminatedsteel core. The coils are insulated fromeach other as well as from the steelcore. A transformer may also consistof a container for winding and coreassembly (called as tank), suitablebushings to take our the terminals, oilconservator to provide oil in thetransformer tank for cooling purposesetc. The figure at left illustrates thebasic construction of a transformer.In all typesof

transformers, core is constructed byassembling (stacking) laminatedsheets of steel, with minimum air-gap

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sheets of steel, with minimum air-gapbetween them (to achieve continuousmagnetic path). The steel used ishaving high silicon content andsometimes heat treated, to providehigh permeability and low hysteresisloss. Laminated sheets of steel areused to reduce eddy current loss. Thesheets are cut in the shape as E,I andL. To avoid high reluctance at joints,laminations are stacked by alternatingthe sides of joint. That is, if joints offirst sheet assembly are at front face,the joints of following assemble arekept at back face.

Types Of Transformers

Transformers can be classified ondifferent basis, like types ofconstruction, types of cooling etc.

(A) On the basis of construction,transformers can be classified into twotypes as; (i) Core type transformer and(ii) Shell type transformer, which aredescribed below.

(I) Core Type Transformer

In core type transformer, windings arecylindrical former wound, mountedon the core limbs as shown in thefigure above. The cylindrical coils havedifferent layers and each layer isinsulated from each other. Materials



like paper, cloth or mica can be usedfor insulation. Low voltage windingsare placed nearer to the core, as theyare easier to insulate.

(Ii) Shell Type Transformer

The coils are former wound andmounted in layers stacked withinsulation between them. A shell typetransformer may have simplerectangular form (as shown in abovefig), or it may have a distributed form.

(B) On the basis of their purpose

1. Step up transformer: Voltageincreases (with subsequentdecrease in current) at secondary.

2. Step down transformer: Voltagedecreases (with subsequentincrease in current) at secondary.

(C) On the basis of type of supply

1. Single phase transformer

2. Three phase transformer

(D) On the basis of their use

1. Power transformer: Used intransmission network, high rating

2. Distribution transformer: Used indistribution network,comparatively lower rating thanthat of power transformers.

3. Instrument transformer: Used inrelay and protection purpose indifferent instruments inindustries

Current transformer (CT)



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(E) On the basis of cooling employed

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2. Oil-filled water cooled type

3. Air blast type (air cooled)

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3 Comments:

SquareAirCoreInductors

Subminiature,HighQfactor,Highprecision

Sophia SmithAPR 28, 2014, 1:54:00 PM

You may think that



electricity is prettystandard but its voltageand frequency variesbetween countries andregions in a single country.Essentially, electricaltransformers are used tochange the voltage ofelectricity so that it issuitable for differentappliances and locations.

Reply

SamrajDwivediJAN 18, 2015,

2:20:00 PM

Yep.. That'scorrect

But hementioned itin topic-purpose

You also needto adjusttransformersso as to fulfillurrequirements...So learningconstructionbecomesimportant

Runthala JaipurMAY 10, 2014, 12:56:00 PM

In essence, a transformer



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changes electrical powerthrough higher in order tominimal voltage utilizingtwo properties ofassociated with electricalpower. Transformercompanies in India,Runthala Industries offersa full range of dry-typetransformersmanufactured

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