Home Engineering What is a Transformer – Types and Working principle of transformer

What is a Transformer – Types and Working principle of transformer

Working principle of transformer

Transformer – What is Transformer ?

Transformer (TR) is a electrical device which is static and transfers electrical energy between two or more circuits through electromagnetic induction. In transformer a varying current in one coil produces a varying magnetic field that in turn induces a varying electromotive force which is known as “EMF” or “voltage” in a 2nd coil. Here in TR, power can be transferred or move between the 2 coils through the magnetic field and that is without a metallic connection between the two circuits. In 1831, Faraday’s law of induction discovered and described this effect. People generally use TRs to increase or decrease the alternating voltages in electric power applications.

Working principle of transformer

Working principle of transformer depends upon the Faraday’s electromagnetic induction law. The law described that the mutual induction phenomenon that is working between two or more winding is the fact that is responsible for power transformation.


We know from Faraday’s laws, “The rate of change of linkage flux with respect to the time is directly proportional to the EMF that induced in the conductor or coil”.

Faraday’s law of induction

So we can write the equation:

E= N d /dt



N = the number of turns

E = Induced EMF

dt = Change in time

d= Change in flux

This was the working principle of transformer.


Types of Transformer

There are various kinds of TR utilized in the electrical power system for different functions, like generation, circulation as well as transmission as well as utilization of electrical power.

The various types of TR are Step up and also Step down Transformer, Power Transformer, Distribution Transformer, Isolation TR making up present as well as Potential TR, Single phase as well as Three phase transformer, Auto TR, and so on.


Step-up and Step-down Transformer

Step up and Step down Transformer This type of transformer is classified on the basis of a variety of turns in the main as well as second windings as well as the generated emf.

Step-up TR changes a low voltage, high current AC right into a high voltage, reduced existing Air Conditioning System in this type of transformer the variety of turns in the secondary winding is higher than the variety of turns in the primary winding. If (V2 > V1) the voltage is elevated on the output side and also is known as Step-up TR Step down TR converts a high main voltage associated with the low present into a reduced voltage, high current. With this sort of TR, the number of turns in the main winding is more than the variety of kip down the additional winding. If (V2 < V1) the voltage level is decreased on the result side and also is called Step down transformer Power TR The power TRs are used in the transmission networks of higher voltages. The rankings of the power transformer are as follows 400 KV, 200 KV, 110 KV, 66 KV, 33 KV. They are generally ranked over 200 MVA. Mostly mounted at the creating stations as well as transmission substations. They are made for optimal performance of 100%. They are larger in dimension as compared to the distribution TR.

At a very high voltage, the power cannot be distributed to the consumer directly, so the power is stepped down to the preferred level with the help of step-down power TR. The TR is not packed fully therefore the core loss happens for the entire day, however the copper loss is based on the lots cycle of the circulation network.

If the power transformer is attached in the transmission network, the lots fluctuation will certainly be very much less as they are not attached at the consumer end straight, however if connected to the circulation network there will certainly be variations in the lots.

The TR is packed for 24 hours at the transmission terminal, therefore, the core and copper loss will certainly occur for the whole day. The power TR is economical when the power is produced at reduced voltage levels. If the level of voltage is increased, then the current of the power transformer is reduced, leading to I2R losses and also the voltage law is additionally raised.

Circulation TR This sort of transformer has reduced ratings like 11 KV, 6.6 KV, 3.3 KV, 440 V and 230 V. They are rated less than 200 MVA and also made use of in the distribution network to provide voltage improvement in the power system by stepping down the voltage degree where the electrical power is distributed and used at the consumer end.

The key coil of the distribution transformer is wound by enamel coated copper or aluminum cable. A thick ribbon of lightweight aluminum as well as copper is used to make additional of the TR which is a high existing, reduced voltage winding. Material fertilized paper as well as oil is made use of for the insulation function.

The oil in the TR is made use of for – Air conditioning.

– Insulating the windings.

– Securing from the dampness.

The different types of the distribution TR are classified on the adhering to basis and are displayed in the figure listed below.

– Placing place.

– Sort of insulation.

– Nature of supply.


The circulation TR less than 33 KV is used in industries as well as 440, 220 V is utilized for the residential objective. It is smaller sized in dimension, very easy to install as well as has reduced magnetic losses and is not always packed completely.

As it does not benefit constant tons throughout 1 day as in the daytime its load goes to its height, and also throughout the evening hours it is really lightly filled thus the performance relies on lots cycle and also is calculated as Throughout the day Efficiency. The distribution transformers are made for maximum efficiency of 60 to 70%.

Uses of Distribution Transformer

– Made use of in pumping terminals where the voltage degree is listed below 33 KV.

– Power supply for the above cords trains amazed with A/C.

– In urban locations, many houses are fed with single-phase distribution TR as well as in rural areas, it might be feasible that a person home calls for one solitary TR relying on the loads.

– Numerous distribution TRs are used for commercial as well as commercial locations.

– Utilized in wind ranches where the electric energy is created by the windmills. There it is made use of as a power collection agency to link the substations which are far from the wind power generation system.


Tool Transformer (Isolation)

– They are normally referred to as a isolation TR. Isolation transformer is an electric gadget made use of to change existing as well as a voltage degree. One of the most common use Isolation TR is to securely isolate the additional winding when the primary has high voltage and also high present supply so that the measuring tool, energy meters or relays which are attached to the second side of the TR will not obtain damaged. The tool TR is more divided into 2 types.

current Transformer (CT).

potential Transformer (PT).

The present as well as prospective TR is discussed below carefully.


Current Transformer

– The Current transformer is made use of for determining and also for the protection. When the current in the circuit is high to use straight to the gauging instrument, the existing TR is utilized to transform the high present into the desired worth of the current required in the circuit.

The key winding of the existing TR is linked in series to the major supply and the various determining instruments like ammeter, voltmeter, wattmeter or safety relay coil. They have exact, current proportion and stage connection to make it possible for the meter accurately on the second side. The term ratio has a great value in CT

. For instance, if its ratio is 2000:5, it means a CT has a result of 5 Ampere when the input current is 2000 amp on the main side. The precision of the current Transformer depends upon numerous aspects like Problem, tons, temperature, stage modification, score, saturation, etc

. In the existing TR, the complete primary current is the vector sum of the excitation present and also the existing equal to the reversal of additional current increased by turn proportion.


Ip– key current.

Is– secondary or reversal existing.

I0– excitation current.

KT– transform ratio.


Potential Transformer

The potential transformer is likewise called as the voltage transformer. The primary winding is linked throughout the High voltage line whose voltage is to be gauged, and all the determining instruments and meters are connected to the secondary side of the TR.

The main feature of the Potential TR is to step down the voltage degree to a risk-free limit or worth. The key winding of the potential TR is earthed or based as a safety and security factor.

As an example, the voltage ratio key to additional is given as 500:120, it means the output voltage is of 120 V when the 500 V is related to the key. The various kinds of potential TR are shown listed below in the figure.

– Electro-magnetic (it is a cable wound TR).

– Capacitor (capacitor voltage transformer CVT makes use of capacitor voltage divider).

– Optical (deal with the electric residential or commercial property if optical materials).

The portion voltage error is given by the formula shown listed below.


Single Phase Transformer

A single-phase transformer is a static gadget, deals with the concept of Faraday’s law of shared Induction. At a constant degree of frequency and also variation of voltage level, the transformer transfers A/C power from one circuit to the other circuit. We know, there are actually two-types of windings in this type of transformer. The winding to which A/C supply is offered is labelled as Key winding and in the second winding, the tons is connected.


Three Stage Transformer

If the three single-phase transformer is taken and connected together with their all the 3 primary winding connected per various other as one and all the three additional windings to each various other, creating as one secondary winding, the TR is stated to behave as a three-phase transformer, that indicates a bank of three single-phase transformer connected with each other which acts as a three-phase TR.

Three-phase supply is primarily utilized for electrical power generation, transmission as well as distribution for industrial function. It is much less expensive to construct three single-phase TRs to create a three-phase TR than to acquire one solitary three-phase TR. The three-phase TR connection can be done by Star (Wye) as well as Delta (Mesh) kind.

The connection of key and also secondary winding can be done by various mixes shown below.

Key Winding Secondary Winding.

Star (Wye) Star.

Delta (mesh) Delta.

Star Delta.

Delta Star.

The combination of the primary winding and also the additional winding is done as star-star, delta-delta, star-delta and also delta-star.


I hope this post will clear your idea about What is Transformer? The different Types of transformers. The working principle of transformer, along with the single phase and three phase transformer.

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