Basics Of Electrical Transformers

Most of us seen electrical transformers and few of us have rough idea about it. Rather than from our information about electrical transformers and it use let us understand the simple basics and its application.

What are Electrical Transformers?

Electrical transformers are machines that transfer electricity from one circuit to another with changing voltage level but no frequency change. Today, they are designed to use AC supply, which means that fluctuation in supply voltage is impacted by the fluctuation in the current. So, an increase in current will bring about an increase in the voltage and vice versa.
Transformers help improve safety and efficiency of power systems by raising and lowering voltage levels as and when needed. They are used in a wide range of residential and industrial applications, primarily and perhaps most importantly in the distribution and regulation of power across long distances.

The Construction of an Electrical Transformer

The three important components of an electrical transformer are

1.Magnetic core,
2.Primary winding,
3.Secondary winding.

The primary winding is the part that is connected to an electrical source, from where magnetic flux is initially produced. These coils are insulated from each other and the main flux is induced in the primary winding from where it is passed to the magnetic core and linked to the transformer’s secondary winding through a low reluctance path.

The core relays the flux to the secondary winding to create a magnetic circuit that closes the flux, and a low reluctance path is placed within the core to maximize flux linkage. The secondary winding helps complete the movement of the flux that begins at the primary side, and using the core reaches the secondary winding. The secondary winding is able to pick momentum because both windings are wound on the same core and hence their magnetic fields help to create motion.
☆In all the types of transformers, the magnetic core is assembled by stacking laminated steel sheets leaving the minimum required air-gap between them to ensure the continuity of the magnetic path.

How Do Transformers Work?

An electrical transformer uses Faraday’s electromagnetic induction law to work – “Rate of change of flux linkage with respect to time is directly proportional to the induced EMF in a conductor or coil”.

A transformer’s physical basis lies in the mutual induction between two circuits that are linked by a common magnetic flux. It is usually equipped with 2 windings: primary and secondary. These windings share a magnetic core that is laminated, and the mutual induction that takes place between these circuits helps transfer electricity from one point to another.

Depending on the amount of linked flux between the primary and secondary windings, there will be different rates of change in flux linkage. To ensure maximum flux linkage, i.e. maximum flux passing through and linking to the secondary winding from the primary, a low reluctance path is placed common to both windings. This leads to greater efficiency in working performance, and forms the core of the transformer.

The application of alternating voltage to the windings in the primary side creates an alternating flux in the core. This links both windings to induce EMF in the primary as well as the secondary side. EMF in the secondary winding causes a current, known as load current, if there is a load connected to the secondary section.

This is how electrical transformers deliver AC power from one circuit (primary) to another (secondary), through the conversion of electrical energy from one value to another, changing the voltage level but not the frequency.

Efficiency and Losses of Electrical Transformer

An electrical transformer does not employ any moving parts to transfer energy which means that there is no friction and hence no windage losses.

However, electric transformers do suffer from negligible copper and iron losses. Copper losses occur due to heat loss during the circulation of currents around the copper windings, resulting in loss of electrical power. This is the greatest loss in the operation of an electrical transformer.

Iron losses are caused by the lagging of the magnetic molecules that lie within the core. This lagging happens in response to the alternating of the magnetic flux which results in friction and this friction produces heat which leads of loss of power in the core. This loss can be greatly reduced if the core is constructed from special steel alloys.

The intensity of power loss determines the efficiency of an electrical transformer and it is represented in terms of power loss between the primary and secondary windings. The resulting efficiency is then calculated in terms of ratio of the power output at the secondary winding to the power input at the primary winding. Ideally, the efficiency of an electrical transformer is anywhere between 94% to 96%

Types of Transformers