# Transformers

A transformer is a device used in the power transmission of electric energy. The transmission current is AC. It is commonly used to increase or decrease the supply voltage without a change in the frequency of AC between circuits. The transformer works on basic principles of electromagnetic induction and mutual induction.

## Introduction

An electromagnetic device is used to transfer electric power from one circuit to another without change in frequency. Transformers are mainly used for stepping up and stepping down the voltages as desired by end users. Its working is based on the principle of mutual induction between two circuits linked by a common magnetic field. Transformers play a major part in the transmission and distribution of AC power.

## Parts of Basic Transformer

A basic transformer consists of following two parts as shown in the figure below

## Parts of Transformer

• Winding Coils
• Core

## Winding Coils

A transformer consists of two conducting winding coils which are separated by a common core. There is no electrical connection between two winding coils and they are connected to each other through magnetic flux. The winding coil which is connected to AC supply and receives electric energy from the AC source is called primary winding. The other winding coil which is connected to the load is called secondary winding.

## Core

The core is made up of high grade iron. The primary and secondary winding coils are wound on the core. A magnetic flux is created in the core when primary winding is connected to AC supply.

## Working Principle of Transformer

The principle of electromagnetic induction between two winding coils forms the basis of working of a transformer. When the primary winding coil is connected to a source of AC voltage, a time varying current starts to flow in primary winding which creates an alternating magnetic field called magnetic flux in the laminated core.
This magnetic flux links with the secondary winding coil due to mutual induction and an EMF is induced in the secondary winding coil because of Faraday's Law of electromagnetic induction and thus, electric energy is transferred from primary winding coil to secondary winding coil.
If the number of turns in secondary winding is less than primary winding, then output voltage will be less than input voltage and if number of turns in secondary winding are more than primary winding, then output voltage will be more than input voltage.

## Working of Transformers

The transformers can be categorized as follows

• Basis of Phase
• Single Phase transformer
• Three Phase transformer
• Basis of Construction
• Shell type transformer
• Core type transformer
• Basis of Working
• Step up transformer
• Step down transformer
• Basis of Power Ratings
• Power transformer
• Distribution transformer

## Single Phase transformer

A single-phase transformer is a device that is capable of transferring electrical energy from one circuit to one or more circuits based on the concept of mutual induction. It comprises two coils – a primary and a secondary coil, which helps to transform the energy. The primary coil is connected to a single-phase supply, while the secondary is connected to a load. A single phase transformer is a type of transformer which operates on single-phase power. A transformer is a passive electrical device that transfers electrical energy from one circuit to another through the process of electromagnetic induction. It is most commonly used to increase (‘step up’) or decrease (‘step down’) voltage levels between circuits. A single phase transformer consists of a magnetic iron core serving as a magnetic transformer part and transformer cooper winding serving as an electrical part. A single phase transformer is a high-efficiency piece of electrical equipment, and its losses are very low because there isn’t any mechanical friction involved in its operation.

## three-phase transformer

three-phase transformer consists of three primary coils and three secondary coils and is represented as 3-phase or 3É¸. A three-phase system can be constructed using three individual identical single-phase transformers, and such a 3-phase transformer is known as the bank of three transformers. On the other hand, the three-phase transformer can be built on a single core. The windings of a transformer can be connected in either delta or wye configurations. The working of the 3-phase system is similar to a single-phase transformer, and they are normally employed in power generation plants.

## Core type transformer

In this transformer, the windings surround a considerable part of the core. Both the windings are bound on two opposite limbs of the core. This transformer is also called single window type transformer.

## Shell type transformer

In this transformer, the core surrounds a major part of the windings. Both the windings are wound on the central limb of the core. This transformer is also called double window type transformer.

## Step up transformer

A transformer that increases the voltage from primary to secondary (more secondary winding turns than primary winding turns) is called a step-up transformer. A step-up transformer is a type of transformer that converts the low voltage (LV) and high current from the primary side of the transformer to the high voltage (HV) and low current value on the secondary side of the transformer.

## Step down transformer

A Step Down Transformer is a device which converts high primary voltage to a low secondary voltage. In a Step Down Transformer, the primary winding of a coil has more turns than the secondary winding. A step-down transformer is a type of transformer that converts the high voltage (HV) and low current from the primary side of the transformer to the low voltage (LV) and high current value on the secondary side of the transformer.

## Power transformer

A power transformer is a passive electromagnetic device that transfers energy from one circuit to another circuit by means of inductive coupling. Power transformers differ from other transformer types in that they are designed to comply with regulatory requirements for mains power interfacing, working at mains voltages and relatively high currents. The most important specification of a power transformer is its primary to secondary transformer galvanic isolation, which is usually specified in kV. This is a fundamental safety aspect in protecting humans from potentially lethal earth fault conditions.

## Distribution transformer

A distribution transformer is also known as a typical kind of isolation transformer. The main function of this transformer is to alter the high voltage to the normal voltage like 240/120 V to use in electric power distribution. In the distribution system, there are different kinds of transformers available like single phase, 3-phase, underground, pad-mounted, pole-mounted transformer.

## Applications Of Transformer

• The transformer transmits electrical energy through wires over long distances.
• Transformers with multiple secondary’s are used in radio and TV receivers which require several different voltages.
• Transformers are used as voltage regulators.
• The power transformer is used to increase otherwise decrease voltage within a power distribution network.
• Distribution transformer is mainly used to decrease a voltage for distribution to commercial & residential users.
• Single-phase transformer is frequently used to provide power for receptacle, residential lighting, AC & heating requirements.
• A three-phase transformer is used to achieve cost-effective power distribution.