TRANSFORMER

A transformer transforms electric energy from a certain voltage and current level to another voltage and current level keeping the frequency of the supply the same. It is because of the availability of the transformer that it is possible to generate energy from where it is available in abundance far away from the load center and the energy so generated at economic voltage levels can be transmitted at economic voltage levels using transformers and the same energy can be utilized at economic and safe voltage levels as required by the devices using the electric energy. The importance of a transformer in an electric energy system can be gauged by the fact that a generation of 1 MW requires transformers of 3 to 3.5 MVA capacity from the power plant to the consumer points. The transformer is also very widely used in electronic circuits i.e. low power low current electronic and control circuits for performing such functions as matching the impedance of a source and the load for maximum power transfer.

 A transformer has normally two windings, the primary and the secondary. The primary is one where the source is connected and across the secondary load is connected. If the secondary voltage is higher than the primary voltage it is known as a step-up transformer and it is known as step down if the secondary voltage is smaller than the primary voltage. However, if the two voltages are equal, it is known as an isolation transformer. The one-to-one transformers are used when it is necessary or desirable to insulate the secondary side of the circuit from the primary circuit; for though both the circuits will then have the same difference of potential between their terminals, they will not necessarily have the same difference of potential to ground. It is to be noted that either of the two windings can be considered as primary while the other then serves as the secondary. The primary is therefore defined as one which receives energy from the supply and the secondary as the one which delivers energy to the load. In general, however, the windings are designated as low tension (LT) or high tension (HT) windings. In its simplest form, the transformer consists of the insulated windings wound on a ferromagnetic core that a current through one of the windings will set up a magnetic flux linking more or less completely with the turns of the other. According to Faraday's laws of electromagnetic induction, an emf is induced in the secondary which is proportional to the number of turns of the secondary and the flux linking the secondary. However, the frequency of the secondary voltage is the same as that of the source.