Transformer - complete information

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Transformer 

Introduction:

The electrical transformer is also one among the important inventions in technological world. Different inventions of the technological world are useless without a transformer. It is named as transformer as it converts or transforms electrical energy from a higher voltage to a lower one. There are hundreds of different  types of transformers which have been designed to handle extremely high voltages and lower ones. 

As far as the discovery is concerned, it was an English scientist named "Michael Faraday". Faraday's discovery of the law of electro-magnetic induction also named as Faraday’s Law, the theory which describes the phenomena of an electrical voltage generated when a coil of wire is wrapped around an iron core.

Joseph Henry, an American scientist is also credited with inventing the concept of electromagnetic induction. An induction coil transformer was developed by Nicholas Callan which helped him to develop a high voltage battery. So, after all we can say that the invention of an electrical transformer does not belong to a particular person. 

Transformer 

Transformer

Transformer is a device which is used for changing the AC voltage. 

A transformer, which increases the AC voltage is called set up transformer and a transformer , which decreases the AC voltage is called step down transformer. 

Principle :

The transformer is based on the principle of mutual induction. i.e., When a magnetic flux linked with coil changes, an induced EMF is produced in the neighbouring coil. 

Construction :

Transformer consists of a rectangular soft iron core which is made up of laminated sheets, well insulated from each other. Two coils P₁P₂  and  S₁S₂ are wounded on the core as shown in the figure. The source of alternating EMF is connected to P₁P₂  and a load resistance R is connected to S₁S₂.

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Transformer - complete information

In step up transformer :-

In this type of transformer, the primary coil consists of a few turns of copper wire where as the secondary coil  consists of large number of turns of a copper wire. 

In step down transformer :-

In this type of transformer, Primary coil consists of a large number of turns, whereas the secondary coil consists of a few number of turns of  copper wire.

Transformer

Theory and Working :-

As the current in primary coil changes,  it changes the magnetic flux associated with the primary coil and hence due to phenomenon of self induction, EMF is produced in the primary coil. In this case ,magnetic flux linked with secondary coil changes and hence due to phenomenon of mutual induction EMF is also produced in the secondary coil.

Let             Np  = number of turns of P₁P₂

                   Ns  =  number of turns of S₁S₂

     dɸ /dt = rate of change of magnetic flux linked with  P₁P₂  or  S₁S₂.

According to the phenomenon of self induction:

                              Ep = -  np.dɸ /dt ...........(1)

According to the phenomenon of mutual induction :

                           Es  = - ns .dɸ /dt ............(2)

Divide  (2)  by  (1),  we get; 

                 
                         Es /Ep =  ns/ np  = K

Where K is a constant and is called transformation ratio.  It is defined as the ratio of the number of turns in the secondary coil to the number of turns in primary coil. 

                                                           OR

Transformation ratio is also defined as the ratio of voltage across secondary coil to the voltage across primary coil. 

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For step up transformer;

                    Es > Ep 

         

                      ns  >  np

For step down transformer; 

                     Es < Ep 

                      ns  <  np 

If Ip  be the current through the primary coil and Is be the current through the secondary coil. 

       

           Input power at any time = EpIp 

          Output power at any time = EsIs

If there is no loss of power; 

             Output power = Input power

                             EsIs = EpIp

                              Es / Ep = Ip/Is = K

Efficiency of the transformer is defined as the ratio of output power to the input power. It is denoted by ƞ.

       ƞ = output power / Input power 

       ƞ  = EsIs/EpIp

NOTE:

 It should be noted that the efficiency for an ideal transformer is 1 or 100%.

 Uses :

1)  It is used in induction furnances.

2) A step down transformer is used for welding purpose. 

3) It is used to regulate voltage for T.V , refrigerator,  computers, A. C. etc. 

4) At the hydro power station, step up transformer is used to increase voltage to several thousand volts and hence current is reduced. Due to this, the power loss will be minimum. 

Advantages :

1)  It offers a good mechanical strength. The coils used in this type of transformers are wound over a symmetrical core section. The way in which they are constructed will give you the advantage of getting better mechanical strength than other types of coils.

2) Transformer has an advantage of preventing iron loss and condensed flux leakage.

3) Due to the presence of steel laminations, they make the transformer efficient for high frequencies.

Disadvantages :

1)  A core type transformer is not good for outdoor use. Unlike oil transformers, it is not protected from corrosion ,rusting and other extreme weather elements which can slowly degrade its inner components and reduce its functioning.

2) It is a noisy transformer . It can produce electrical noise that arises from arcing on the covers. It can also produce audible noise. 

Conclusion:

The article discussed above provides you information about a core type electrical transformer . It also provides you information related to its discovery,  construction , Theory, advantages ,disadvantages and it's working. The article clears you the idea of a transformer.