What is a transformer and how does it work?

The transformers are electrical components that use electromagnetic induction to modify the electrical tension (voltage) of an alternating current maintaining the power (watts).

In this article we will study the operating principles of electrical transformers and what they are used for.

Transformer operation

The operation of electric transformers is based on the electromagnetic inductiona phenomenon discovered by Michael Faraday in 1831 and described mathematically in the Maxwell–Faraday equation.

The electromagnetic induction Consists of the production of an electric current in a conductive material subjected to changing magnetic field.

Using this phenomenon, electricity can be generated by the movement of a magnetic field (magnet). This is how electricity is produced in hydroelectric, thermal, wind power plants, dynamos, etc.

In transformers it is used to transfer electrical energy between two circuits by modifying the voltage of the transferred current.

Basically, a transformer consists of a metal core, usually made of iron, to which two circuits are connected by winding the wiring at the ends. Two windings are thus formed: primary and secondary.

The primary winding receives a alternating electric current. The spirals around the iron core create a magnetic field, as the current is alternating, in each cycle the magnetic field changes and induces electricity in the secondary winding.

The voltage change is proportional to the number of turns of the spirals of each winding:

  • step down transformer: the primary winding has more turns than the secondary and the voltage decreases.
  • step-up transformer: The secondary winding has more turns than the primary. The tension increases.
Scheme of an electrical transformer
Schematic of a step-down electrical transformer

Transformer Applications

One of the main applications of electrical transformers is in the transportation of electricity from production plants to places of consumption (homes and industry).

Generally, electricity has to travel long distances and to minimize losses due to the Joule effect, high voltage electricity is used at the output of the production plants.

Before being used, it is transformed at various points in the electrical network until it reaches the appropriate voltage levels depending on whether it is for domestic or industrial use.

Schematically, electricity is passed through step-up transformers at the exit of the production plants. In this way the voltage is raised and it can be transported over great distances.

Later it comes to transformer substations where are they used step-down transformers. From here they go to smaller local transformers, such as those found on power poles, where the voltage is lowered again before final use.

Other uses

Electrical transformers are used by a wide variety of devices and appliances that work with electrical voltage levels different from those provided by the network. These appliances have their own transformer inside to transform the electricity to the appropriate levels before it enters the electrical circuit of the appliance.

Voltage inverters are a type of electrical transformer that is also well known and used.

Another use is in safety devicesperhaps the best known is the differentiala device located between the internal and external electrical network of the houses and that, using transformers, compares the electrical intensity that enters with the intensity that leaves and if there is a difference greater than 10 mA, the entire circuit is disconnected to avoid possible accidents.

Go up