What Is A Transformer?

Did you know that among the many reasons why you are able to read this article are the invention and evolution of transformers? Yes, that’s right, even though we do not pay much heed to it. Transformers not only transmit electricity to our houses but also run industries where most of the devices we use are manufactured. Perhaps, they need to be given more credit, and they need to be learned about.

This article will give you an insight into what transformers are, how they work, and the wide range of the types that exist around the world. Without waiting further, let us dive into all there is to know about a transformer.



A transformer is a static electrical machine that transfers alternating current (AC) from one circuit to another at a constant frequency. The AC voltage can be fluctuated as per design.

A transformer works on the principles of Faraday’s law of induction which states that a magnetic field interacts with electric current to produce electromotive force or EMF. The two circuits in the transformer usually do not have a conductive connection.


A standard transformer consists of three main components: primary winding, a secondary winding, and the main core.

Primary winding 

This primary winding coil is wound around one side of the core and is connected to a live source of AC power. It is called the primary winding because the alternating current is fed to it first.

Secondary winding

The secondary winding is also a coil that is wound around the other side of the core. The EMF is induced in this winding.

The core

The magnetic core is made of laminated steel sheets, unless specified by the type of transformer. This acts as a path of low reluctance for the magnetic field.



The foundation of a transformer is set in Faraday’s law of electromagnetic induction. Michael Faraday, often referred to as the father of electricity, was an English scientist who discovered electromagnetism. Upon further work on his findings, the first transformer was invented in 1884 in England. Two years after its invention, this transformer was used in the first AC power plant named the Rome-Cerchi plant. As a result, power was supplied domestically in 1886.

Over the decades, advancements in the technology of transformers have occurred, making it safer to use, more efficient, and much more accessible than before. However, the most basic elements of a transformer still stay the same as they were when it was first invented.

How does it work?


The power is provided to the transformer through the primary winding. Alternating current passes through it, giving rise to a fluctuating magnetic flux around the primary winding. This flux gives rise to EMF in the secondary coil. The core provides a route for the magnetic field.

If the power to the secondary coil is turned off, the AC will flow directly through it.

Types of transformers

Types based on voltage


The different types of transformers based on voltage are the most fundamental classification of transformers. The difference is based on whether they increase voltage or decrease. The two types are step-up transformer and step-down transformer, respectively.

Step-up transformer

Step-up transformers work by increasing the voltage on the secondary coil of the transformer. In a step-up transformer, the secondary winding takes more turns around the coil than the primary winding. It is most commonly used in the transmission of power so high voltage can be transformed.

Step-down transformer

A step-down transformer decreases the voltage on the secondary coil. The phenomenon is achieved by reducing the number of turns in the secondary winding so that they are lower than the primary winding. A step-down transformer is also used in transmission lines.

Types based on usage

Transformers are also classified based on where they are used, domestically or on an industrial scale. The power transformer is used to transmit power, while the distribution transformer is used for both industries and housing.

Power transformer

A power transformer is a massive machine used in the transmission network of power. It works at high voltages ranging from 110 Kilo Volts to 600 Kilo Volts. Higher voltages need more insulation which contributes to the massive size of this transformer, its 100% efficiency, and its ability to handle heavy loads.

Distribution transformer

A distribution transformer is used to distribute lower voltage to provide power to the end-user. The distribution transformer is used in both industries and domestic housing.

It has a lower insulation level than a power transformer. Hence, it works at a lower efficiency of 50-60%.

Distribution transformers are further divided into two categories based on the insulation type; the two types are liquid immersed and dry.

Liquid immersed transformer

A liquid immersed transformer contains oil inside it to act as a coolant. The windings are immersed in the insulation oil to maintain a certain temperature. These transformers must be kept in open spaces, safety measures should be taken in the area, and constant maintenance of these transformers is also essential.

Dry-type transformer

A dry-type transformer does not use oil as a coolant. Instead, the air is used to maintain temperatures. These are often used inside buildings.

Types based on core medium

This category has its foundation in the difference of the core between the primary and secondary winding. The two types of cores are air core and iron core.

Air core

An air core transformer has the flux linkage between the primary and secondary core through the air. The windings are placed on magnetic strips since a core is absent. These transformers are not preferred due to low inductance, but the hysteresis and eddy currents are non-existent in an air core transformer. This is a significant factor that impacts the decision to buy an air core transformer.

Iron core

In an iron core transformer, both the primary and secondary windings are placed on an iron core, causing a linkage of flux across both. The reluctance to linkage is incredibly low, making this transformer highly efficient and widely preferred over its counterpart.

Instrument transformers


As the name gives away, these transformers are used as instruments to record voltage or current where it is hard to execute that. There are two types that work differently but achieve the same purpose: stepping down the current and voltage for measurement. The types are current transformer and potential transformer.

Current transformer

A current transformer acts as a barrier between the ammeters of the coil and high current lines. It steps down the value by a specific ratio that is later adjusted.

Potential transformer

A potential transformer works quite similarly to a power or distribution transformer. The difference is that this has a lower range for both current and voltage.


The science of transformers is a lot more complex than an article could summon, but this does provide a lot of inside information about how we receive electricity at our homes and the several other applications of transformers.

It is also incredible how a small discovery of electromagnetism has led to and will continue to transform human lives over the decades. The importance of transformers is often overlooked when in reality, this futuristic era would cease to exist without transformers.