WORKING PRINCIPLE OF A TRANSFORMER

  WORKING PRINCIPLE OF TRANSFORMER

 A transformer is a static (or stationary) piece of apparatus by means of which electric power in one circuit is transformed into electric power of the same frequency in another circuit. It can raise or lower the voltage in a circuit but with a correspond- ing decrease or increase in current. The physical basis of a transformer is mutual induction between two circuits linked by a common magnetic flux. In its simplest form, it consists of two inductive coils which are electrically separated but magnetically linked through a path of low reluctance as shown in Fig. 32.1. The two coils possess high mutual v inductance. If one coil is connected to a source of alternating voltage, an alternating flux is set up in v the laminated core, most of which is linked with the other coil in which it produces mutually-in- d u ced e.m.f. (according to Faraday’s Laws of Electromagnetic Induction e = MdI/dt). If the second coil circuit is closed, a current flows in it and so electric energy is transferred (entirely magnetically) from the first coil to the second coil. The first coil, in which electric energy is fed from the a.c. supply mains, is called primary winding and the other from which energy is drawn out, is called secondary winding. In brief, a transformer is a device that.

1. transfers electric power from one circuit to another

2. it does so without a change of frequency

3. it accomplishes this by electromagnetic induction and

4. where the two electric circuits are in mutual inductive influence of each other.

32.2. Transformer Construction

The simple elements of a transformer

consist of two coils having mutual

inductance and a laminated steel core. The

two coils are insulated from each other and

the steel core. Other necessary parts are :

some suitable container for assembled core

and windings ; a suitable medium for

insulating the core and its windings from

its container ; suitable bushings (either of

porcelain, oil- filled or capacitor- type) for

insulating and bringing out the terminals

of windings from the tank. In all types of transformers, the core is constructed of transformer sheet steel laminations assembled to provide a continuous magnetic path with a minimum of air- gap included. The steel used is of high silicon content, sometimes heat treated to produce a high permeability and a low hysteresis loss.

Thank you.

Written by Abhishek Singh E.E