TRANSFORMERS

PRINCIPLE OF TRANSFORMER OPERATION
A transformer is a static device which consists of two or more stationary electric circuits interlinked by a common magnetic circuit for the purpose of transferring electrical energy between them. the transfer of energy from one circuit to another takes place without a change in frequency.

 consider two coils 1 and coils 2 wound on a simple magnetic circuit as shown in fig . these two coils are insulated from each other and there is no electrical connection between them .Let T1 and T2 be the number of turns in coils 1 and 2 respectively. when a source of alternating current produces an alternating flux 0m in the magnetic circuit.the mean path of this flux is shown in figure  by the dotted line. this alternating flux links the turns T1 of coil 1 and induces in them an alternating voltage E1 by self-induction. let us make the following simplifying assumptions for an ideal transformer:
(a) there are no losses either in the electric circuits or in the magnetic circuit.
(b) the whole of the magnetic flux o is confined to the magnetic circuit,so that there is no leakage flux.
(c)the permeability of the core is infinite.
 Thus, all the flux produced by coil 1 also linkes T2 turns of coils 2 and induced in them a voltage E2 by mutual induction . If coil 2 is connected to a load then an alternating current will flow through it and energy will be delivered to the load. Thus, electrical energy is transferred from coil 1 to coil 2 y a common magnetic circuit.since there is no  relative motion between the coils,the frequency of the induced voltage in coil 2 is exactly the same as the frequency of the applied voltage to coil1

coil 1 which receives energy from the source energy from the source of a.c supply is called the primary  coil or primary winding or simply the primary,coil 2,which is connected to load and delivers energy to the load, is called the secondary. the circuit symbol for a two-winding or simply the secondary. the circuit symbol for a two - winding transformer is shown in fig the vertical bars are used to signify tight magnetic coupling between the windings.


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