The Working Principle of Transformer

 

The Working Principle of Transformer:

A transformer is a machine but it does not have any moving part that is why a transformer is referred to as a static machine a transformer has three main parts, two windings and a metallic core on which the windings are wounded. windings are in the form of coil made of a good conductor of current the windings of the transformer play a main role in the machine the winding coils behave as an inductor when an alternating current is allowed to flow through any of the windings there will be an alternating flux produced surrounding the winding the magnitude of this flux is proportional to the magnitude of the current flowing through the winding the direction of the flux is according to the direction of current the direction of the current in the winding can be found out by applying right hand grip rule this rule states that when we grip our right hand with stretching the thumb along the axis of coil or winding and other four figures along the direction of current in the coil then the thumb indicates the direction of produce flux inside the coil along the axis this flux becomes maximum in magnitude when current reaches its maximum for one half cycle of the alternating current wave the flux becomes zero when current in the coil crosses 0 axis again for next half cycle the flux becomes maximum but in opposite direction when current reaches to its  

reverse maxima in this way alternating current produces continually varying flux surrounding the winding the flux lines link the winding itself and the flux is varying so they will be self-induced EMF across the winding this phenomenon is due to faraday’s laws of electromagnetic induction this induced EMF or voltage whatever you say is same in magnitude but opposite in polarity of the supply voltage.   

 

 supplied alternating voltage causes alternating current in the winding which produces continually varying flux inside and outside the winding this continually varying flux produces induced EMF across the winding so we can say that the supply voltage is caused and induced voltage in the winding is  an effect on this cause hence according to Lenz’s law this induced voltage will be in opposite polarity of supply voltage since according to Lenz’s law effect always opposes ‘cause this self-induced voltage across the winding does not depend upon the number of turns in the winding but depends on the supply voltage but the voltage induced per turn depends on the number of turns in the winding this is nothing but induced EMF divided by the number of turns in the winding we have said that there is another winding in the most basic transformer but till now we have not discussed it now we are coming to second winding in the transformer supposing one separate winding is brought nearer to the first winding then this second winding gets linked with a portion of varying flux of first winding due to this varying flux linkage there will also be an induced EMF across it. this induced EMF would be quite small because the flux linkages are small hence the rate of change of flux linkages is also small and according to faradays laws induced EMF across a coil is directly proportional to the rate of change of flux linkage. If now we connect a close circuit across the second winding we will get a very tiny current through the circuit

Provided the second winding is placed much nearer to the first so we have seen that some portion of the input power is transformed to output through the second winding this is because some portion of the generated flux of the first winding is linked with the second. now if we want to transform maximum electric power from first winding to second winding we have to link maximum flux of first winding two-second winding this is done by placing a low reluctant magnetic core in between these windings steel is a well-known low reluctant magnetic material so we normally use steel for making low reluctant magnetic core in the transformer as soon as we place the steel core in between these windings nearly the entire flux which were surrounding the first winding will be concentrated inside the core and link with the second winding as nearly the same flux links with second whining now the rate of change of flux with respect to time is equal in both windings since as per Faraday’s law of electromagnetic induction induced EMF across a conductor is directly proportional to the rate of change of flux linkage the voltage induced per turn in both windings will be the same we have already explained that voltage induced across the first winding is same as the supply voltage. Here we consider there is no voltage drop between the supply terminals and the first winding. This is an ideal case for theoretical purposes we will consider that condition.  

 

 as this first winding is connected with supply it is referred to as primary winding now if this primary winding has N1 number of turns and supply voltage or induced voltage across the primary winding is V1 that voltage per turn in the primary winding is( V1 /N 1) so far we have understood that exactly this V1/N1 voltage will appear across each turn of second winding so if this second winding has N2 number of turns than the total voltage across the second winding is N2xV1/N1 and let us say this is V2 if now any close circuit is connected across the second winding it will provide voltage V2 across the circuit and due to the voltage there will be current flowing through the circuit normally in a transformer the second winding is connected with load circuit this winding is referred to as secondary

if the number of turns in the secondary winding is not equal to that of primary winding that is if

N2≠N1 then secondary the voltage is not equal to the primary voltage

Now if N 2 is greater than N1 the secondary voltage will be more than the primary voltage on the other hand if N 2 is less than one the secondary voltage is less than the primary voltage then the transformer is called a step-up transformer and the latter is called a step-down transformer this is the most basic theory of a transformer hope you understand thank you