TRANSFORMER

This is the static device which is used to change the magnitude of  an alternating current(A.C) from either low to higher magnitude or from high to lower  magnitude by using the two operational principles,principle of electromagnetism together with the principle of mutual induction.

CLASSIFICATION OF TRANSFORMER

1.Classification according to the application

a.Step up transformer

This is the type of transformer which is used to change the magnitude of an alternating current from lower magnitude to higher magnitude.

This type of transformer is characterized by having large number of turns on the coil of the output circuit and small number of turns on the coil of the  input circuit.

This type of transformers are mostly used for the transmission of alternating current from the power plant into the transmission lines in order to overcome the effects of power loss.

b.Step down transformer

This is the type of transformer  which is used to change the magnitude of an alternating current(A.C) from high to lower magnitude .

This type of transformer is characterized by having large number of turns on the coil of the input circuit and smaller number of turns on its output circuit.

This type of transformer is used for the distribution of power from the transmission poles to the customers.

2.Classification according to the type of construction.

a.Core type transformer

In this type of transformers the core is in the form of rectangular frame with the turns wound on the limbs of the core. A single phase transformer may be designed with the number of turns over the limb of the input circuit and the turns over the limb of the output circuit. But on doing so, the leakage reactance will be large leading to a heavy power loss. In actual practice both the limbs of the frame contains half of number of turns on input circuit and on the output circuit. By doing, so the leakage reactance can be reduced.

The low voltage windings are placed inside the high voltage windings. This is to reduce the insulation requirement of high voltage windings.

b.Shell type transformer

In shell type transformers, the core has three limbs: a central limb and two side limbs. The windings are made around the central limb. The width of the central limb is twice that of the side limb. Both the HV and LV windings are divided into number of coils and are arranged alternatively. The HV windings are sandwiched between the LV windings.

PRINCIPLE OF WORKING OF TRANSFORMER

The transformer operational is based on the two principles namely as:-

1.Electromagnetism and

2.Mutual induction.

1.Electromagnetism

When the current is flowing through the conductor,there is a
magnetic fluxes produced around it.The direction of the fluxes produced can be determined by using Maxwell Cork Screw Principle.

The law states that,if the cock is screwing then the direction of motion will show the direction of the current and the direction of the rotation will show the direction of the fluxes.

The magnitude of the flues produced is directly proportional with the length of the conductor.

Thus to increase the length of the conductor,the conductor should be coiled into a number of windings .

ELECTROMAGNETISM IN TRANSFORMER

When the input A.C voltage is allowed to inter the input circuit,the fluxes will produced on the primary coil but its magnitude depends on the number of windings.

Thus the fluxes produced will link with the core toward the secondary coil.

2.MUTUAL INDUCTION

This is the situation where by the EMF is induced in the coil due to the current carried on the neighbour coil.

MUTUAL INDUCTION IN TRANSFORMER

Once the flues links with the coil,the secondary coil will be magnetized and hence the EMF will be produced on the secondary circuit as output.