Definition of a transformer

A transformer is an electrical device for changing current or voltage between different parts of an electrical circuit. Dual wound transformers create isolation between circuits as there is no electrical connection. Used essentially for electrical safety with power tools.

Theory of a transformer

A transformer consists essentially of a magnetic circuit linking with two distinct windings, the primary and secondary. When the primary winding is connected to an AC supply an alternating flux is set up in the transformers core, and this flux linking with the secondary will induce an alternating emf in the in the secondary winding.

Construction of a transformer

A transformer normally consists of an enamelled copper or aluminium wire would around an iron core. Steel laminations are often fitted around the core to reduce losses and improve efficiency.

There are two main types of double wound transformers, core type (single magnetic circuit) and shell type (twin magnetic circuit).

Uses of a transformer

A major advantage of AC distribution is the ease with which alternating voltage can be increased or reduced. It is a common practice within the United Kingdom to generate electricity at 11000v and then by the means of transformers increase it up to to 33000v or even 132000v. Electricity is most easily carried at high 3ph voltages around the country. Medium size transformers then allow high voltage to stepped down to safer lower 1ph voltages for use in the home and industry.

As medium size transformers are normally 97 or 98 percent efficient there are very few losses when stepping down from high voltage. Furthermore as transformers have no moving parts the level of supervision, maintenance and natural failure is very low.