What is Transformer,Its Working Principle and Constructions

What is Transformer?

A device that transfers electrical energy from one circuit to another through the process of electromagnetic induction.

Figure 1

Working Principle of Transformer:

The principle of mutual induction states that when two coils are inductively coupled and if current in one coil changed uniformly than an emf induced in the other coil. This emf can drive a current, when a closed path is provided to it. The transformer work on the same principle. 

It consist of two inductive coils which are electrically separated but linked through a common magnetic circuit. Both these coils are high mutual inductance. One of two coils are connected to a source of alternating voltage. The coil in which electrical energy is fed with help of source is called primary winding and the electrical energy is transformed to this winding is drawn out to a load. This winding is secondary winding and it is connected to a load. N1 is number of turns of primary winding and N2 is number of turns of secondary winding. When primary winding is delighted by an alternating voltage, it circulated an alternating current through which alternating flux produced which complete its path through common magnetic core. Now alternating flux linked with secondary winding, as flux is alternating so mutual induced emf get developed in the secondary winding. If load is connected to the secondary winding, this emf drives a current through it.

Figure 2

Construction of Transformer:

It consist of magnetic and electric circuit.

• Magnetic Circuit
• Electric Circuit

Magnetic Circuit:

It has two parts magnetic core and winding or coils.

The core of the transformer is either a square or rectangular in size.

Figure 3 Core of Transformer

It is further divided into two parts

• Limb
• Yoke

Limb:A vertical portion on which coil are wound is known as limb.

Yoke:The top and bottom horizontal portion is known as yoke.

Cope is made up of the lamination.Because of laminated type of construction,eddy current losses get minimised. High grade silicon steel laminations are used.All lamination are varnished.Lamination are overlapped so that to avoid gap at the joint.Generally L shaped or I shaped laminations are used and the different cross sections of limb used practically.

Figure 4

Electric Circuit:

The construction of the electric circuit of the transformer consists of primary and secondary windings usually made of copper. The Conductors of the rectangular cross-section are generally used for low voltages winding and also for the high voltage winding for large transformers. Conductors of the circular cross-sectional area are used for high voltage winding in the small transformer.

Figure 5