A transformer is an electrical device which is used for changing (transform) the a.c. voltages. It is based on the principal of mutual induction. A transformer is essentially an a.c. device. It cannot work on d.c. . A transformer changes only a.c. voltages/currents.

Transformer cross-section showing primary and secondary windings is a few inches tall (approximately 10 cm).

There are two types of transformer:-

Step up transformer

Step down transformer

A transformer which increases the a.c. voltage is called step up transformer.

A transformer which decreases the a.c. voltage is called step down transformer.

There are many types of energy loses in transformer. Major sources of energy lose are:-copper loss, iron loss, leakage of magnetic flux, hystresis loss and magnetostriction. We cannot obtain full input power as output power because of energy loses. Output power in a transformer is 90% of the input power.

It is used:-

as voltage regulator

For transmission of a.c.

For welding purposes etc

REVIEW OF LITERATURE

1) Development of Economical Analysis and Technical Solutions for Efficient Distribution Transformers

M.L.B. Martinez, , H.R.P.M. de Oliveira

Transformers are equipments applied to electrical systems to adjust voltage levels for consumption, distribution, transmission, and generation needs. Actual technology indicates that they are responsible for approximately one third of total network losses. These losses can be accounted as power utility costs, costs to society and to the environment itself. The aim of this paper is to study the relationship between the transformer costs and its losses. A method for collecting cost data and for building cost surfaces – the so called “Production and Total Cost Surfaces” is presented. The economic analysis of transformer designs considers a variation of the reference data of the main constructive parameters of a standard transformer. Therefore, changes are introduced, amongst others, in the core dimensions, such as the column circumscribed area, its diameter and the yoke area. This approach helps the power utilities to purchase equipment according to the forecast demand, decreasing the total network losses.

2) Reducing Heat in a Transformer and increasing its Loading Capacity, by decreasing the Percentage of Harmonics and Reactive Power

Submitted by A.F. Picanço

By M Duta et al

The paper deals with a situation that has taken place while working with average voltage transformers in a cement factory. Due to the adjustable drives in the production flow, both with thyristors and with variable frequency, current harmonics are introduced in the electrical network of the consumer. These harmonics distort the wave forms of the supply voltage and of the current flowing through the distribution equipment of the system. There are presented the results of the measurements obtained at a cement factory belonging to the HEIDELBERG concern in Romania. By using a modern installation for an automated filtering and compensation of the reactive energy, the current gets cleaned of harmonics and the power factor increases, which makes it possible for the transformer to be efficiently loaded at a charge as close as possible to the nominal load.

3) Selecting least-cost, energy efficient distribution transformers

Submitted by C de Salles

The SEEDT project, cooperation between energy agencies, institutes, electrical utilities, transformer manufacturers and academic institutes, presents its new selection guide for energy efficient distribution transformers (EEDT).

The guide describes losses in transformers, technical solutions for improving them and their energy saving potential for the European Union. It continues to describe the cost of losses, and presents methods for economic evaluation of investment decisions in high efficiency. The guide concludes by proposing policy support mechanisms for EEDT.

This guide is for you if you are:

working in an electricity distribution company,

an industry, commercial or public organisation wanting to purchase a distribution transformer,

a facility manager,

a planner or equipment installer in charge of technical planning or preparing the purchase of a distribution transformer in a client’s organisation.

This guide supports you in:

purchasing a distribution transformer for the least lifecycle cost,

achieving further energy an