Working Principle Of Transformer | Step Up [Transformer Diagram] | How to Reduction [Transformer Losses]

Working Principle Of Transformer

Working Principle of transformer
Work­ing prin­ci­ple of transformer

Working Principle of Transformer 

What is Transformer?

A trans­former is a sta­t­ic elec­tric machine that con­verts elec­tric pow­er from one cir­cuit to anoth­er cir­cuit with­out chang­ing the frequency 

Trans­former Work­ing as mag­net­ic induc­tion Principal 

The device which is used to step­ping up or step­ping down of volt­ages is known as trans­former they can step up or step-down alter­nat­ing volt­age only 

Transformer windings:-

  • Pri­ma­ry Winding
  • Sec­ondary Winding 
  • Lam­i­nat­ed iron core

Primary winding:-

. Any wind­ing we give A.C SUPPLY that wind­ing is called pri­ma­ry winding

Secondary winding:-

The wind­ing from which we take the pow­er sup­ply is called sec­ondary winding

Laminated iron core:- 

Both pri­ma­ry wind­ing and sec­ondary wind­ing are wrapped around the iron core at both ends 

Working Principle of Transformer Full Explanation

Working Principle Of Transformer
Work­ing Prin­ci­ple Of Transformer

Work­ing Prin­ci­ple of trans­former When giv­ing A.C sup­ply to pri­ma­ry wind­ing, alter­nat­ing mag­net­ic flux is gen­er­at­ed in the iron core.This alter­nat­ing mag­net­ic flux cuts both the pri­ma­ry wind­ing and the sec­ondary wind­ing thus form­ing elec­tro mag­net­ic flux in the sec­ondary wind­ing accord­ing to the self induc­tion principle. 

Now when the load is con­nect­ed to the sec­ondary wind­ing the cur­rent goes through the load.Thus elec­tric pow­er is trans­ferred from the pri­ma­ry wind­ing to the sec­ondary winding 

The emf that can be induced in wind­ing depends on the num­ber of in the winding. 

1.Step Up Transformer Diagram 

Step Up Transformer Diagram
Step up Trans­former Diagram

Step up Trans­former Dia­gram is shown above picture

If the num­ber of wound in the sec­ondary wind­ing is greater than the num­ber of wound in the pri­ma­ry wind­ing then the sec­ondary wind­ing induced elec­tro mag­net­ic flux is greater than the pri­ma­ry wind­ing volt­age Step up Transformer 

Clear expla­na­tion at elec­tri­cal

read this link Read more

Step down Transformer 

Step down Transformer
Step down Transformer 

Than the num­ber of wound in the sec­ondary wind­ing If the num­ber of cir­cuits in the pri­ma­ry wind­ing is less than the elec­tro mag­net­ic flux induced in the sec­ondary wind­ing is less than the pri­ma­ry wind­ing volt­age we call this step down Transformer 


1.Load Loss 

2.Fixed Loss 

Load loss

Load loss occurs when cur­rent pass­es through pri­ma­ry wind­ing and sec­ondary winding.These loss­es depend on the pri­ma­ry and sec­ondary wind­ing and resistance.These loss­es vary depend­ing on the load 


l= con­duc­tor length 

P=conductor resistance 

a=conductor cross sec­tion area 

Copper Loss

COPPER LOSS =I1squareR1+I2squareR2

I1=primary cur­rent

I2=secondary cur­rent

R1=primary resis­tance

R2=secondary resis­tance

Fixed Loss

hys­tere­sis loss and eddy cur­rent loss called as fixed loss 

Hysteresis Loss

When the alter­nat­ing flux is gen­er­at­ed in the trans­former mag­net­ic core, a cycle of mag­ne­ti­za­tion and de-mag­ne­ti­za­tion occurs in the core.This caus­es ener­gy loss. This ener­gy loss is called hys­tere­sis loss 

Kh = Hys­tere­sis constant 

Bm = Max­i­mum flux density 

f = frequency 

V = core volume 

Eddy current loss 

When the trans­former core is sub­ject­ed to the A.C mag­net­ic field, the core trig­gers an emf.This emf core caus­es an eddy cur­rent This eddy cur­rent caus­es eddy cur­rent loss 

Eddy cur­rent loss = Ke Bm f square t square watts/m cube 

Ke = eddy cur­rent constant 

t = core thickness 


Bm=maximum flux density 

Reduction in Transformer Losses 

Trans­former loss­es can be min­i­mized depend­ing on the design and lay­out of the transformer.Core loss is min­i­mized by using sil­i­con steel core 

Using core amor­phous steel can also reduce core loss.Using a thin lam­i­nat­ed core and step­per joint core can reduce core losses 

Since cop­per resis­tance val­ue is low­er than alu­minum, cop­per wind­ing can be used to reduce cop­per loss 

When oper­at­ing more than two trans­form­ers in par­al­lel, the low-load trans­former switch­es off and dis­trib­utes its load to the oth­er transformer.Thus the switch off trans­former core loss becomes zero 

Types of Transformer 

1.Core type

2.Shell type

1.Core Type Transformer 

Core type con­struc­tion is more suit­able for High volt­age trans­former coil. The coils are wound around the two limbs of a rec­tan­gu­lar mag­net­ic core each limbs car­ries one half the pri­ma­ry wind­ing and one of the sec­ondary wind­ing so as to reduce the leak­age reac­tance. Insu­la­tion are pro­vid­ed between the pri­ma­ry and sec­ondary windings 

The L.V wind­ing is wound next to the insu­lat­ed core and H.V wind­ing is wound over the L.V wind­ing inorder to reduce the amount of insu­la­tion required 

Small trans­form­ers may have core of rec­tan­gu­lar or square cross-sec­tion with rec­tan­gu­lar or cir­cu­lar coils in case of large size trans­former stepped cru­ci­form core with cir­cu­lar coil is employed 

This type of cores are built with dif­fer­ent sizes of lam­i­na­tions. The cir­cu­lar coils with cru­ci­form core pro­vide more mechan­i­cal strength espe­cial­ly when short-cir­cuit occurs oth­er advan­tage of using cru­ci­form core are reduced mean length of turns result­ing in reduced cop­per Loss 

Shell type transformer 

Shell type con­struc­tion is more suit­able for low volt­age trans­form­ers. The coils are wound on the cen­tral limb of a three limb core the entire flux pass­es through the cen­tral limb the size of the out­er limb is half of the cen­tral limb. In this type trans­former sand­wich wind­ing is used 

The shell type trans­former is built up with E and I shape cores. The lam­i­nat­ed E and I cores are assem­bled to form the mag­nat­ic cir­cuit it con­sists of three limbs one limb is at the cen­tre and two limbs are outer 

The H.V wind­ings and L.V wind­ings are placed over the cen­tral limb the wind­ings are cov­ered on both sides by cores 


1*Less mag­net­ic loss 

*less leak­age reactance 

*Greater mechan­i­cal strength 

*Bet­ter cool­ing facility 

*Less mag­net­ic current 


*Dif­fi­cult for manufacturing

*Greater dif­fi­cul­ty in car­ry­ing out repairs

Why Transformer Rating in KVA? 

The capac­i­ty of the trans­former is always expressed in KVA. Rat­ing of the trans­former is defined as the max­i­mum pow­er in KVA that the trans­former can han­dle with­out over­heat­ing of its wind­ings when rat­ed volt­age at rat­ed fre­quen­cy is applied to the pri­ma­ry windings 

The cop­per Loss of a trans­former depends on volt­age. Hence total loss­es depends on volt ampere only and it is inde­pen­dent of load pow­er­fac­tor. That is why the rat­ing of trans­former is giv­en in KVA and not in KW 

Uses Of Two Winding Transformer 

1.It is used as Auto Trans­former starters for start­ing the induc­tion motor 

2.It is used as instru­ment trans­former for increas­ing the range of meters 

3.It is used in night lamp 

4.It is used in Pow­er Sup­ply for Elec­tron­ic circuit 

5.In gen­er­at­ing sta­tion the trans­former step up the volt­age for transmission 

Do you know Three phase Trans­former work­ing? Read more

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