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Working Principle of a Transformer

Working Principle of a Transformer

Most of the electronic devices or circuits used in today's world have different transformer applications. Therefore, it is significant to understand the definition, application, the working mechanism of transformers, and their end-to-end, construction in distinctive analog circuits.

What is Transformer?

The transformer is a static device used to step up and step down voltage levels, which works by transmitting electric current to a wire through a fluctuating magnetic field.

However, when we learn briefer about transformers and associate it with electrical energy, we can define transformer as a static device that fluctuate the supply of voltage in different analog circuits. The transformer is a voltage regulator that is widely used in the circulation and conduction of ac (alternating current) supply.

The concept of a basic transformer was first discovered by Michael Faraday in 1831 and later the idea was supported and developed by many other intellectual scientific researchers.

Working Principle of a Transformer

However, the generic motive of bringing the concept of transformers was to restore a balance between the current generated at high level voltages and its consumption which was done at low level voltages.

Applications of Transformer

The applications of the transformer are as follows:

  1. The transformer transfers the stream of current energy via wires over long distances.
  2. Transformers are used in our day to day application, which requires the supply of different voltage rates. For instance, radio, TV, etc.
  3. Transformers are used widely as voltage controllers in almost all electrical appliances.

Working Principle of a Transformer

The mechanism of transformer's working has originated from the concept of Faraday's Law of Mutual Induction or Electromagnetic induction that occurs between two circuits connected by a mutual magnetic flux. Before heading on to the working of the transformer, let's discover the mechanism of electromagnetic induction.

Mechanism of Electromagnetic Induction

Whenever current passes through your electric wire coil, it produces a magnetic field or magnetic flux all across its surface. The magnetic flux or magnetic field for any material is defined as the temporary medium by which magnetized forces are transferred between electric materials.

We often unknowingly encounter these forces in our day to day life, such as some ferromagnetic materials (iron, cobalt, or nickel) acts as temporary magnets in the presence of permanent magnets that pull and starts attracting or repelling other magnets or electric materials.

However, the strength of the magnetic ?eld is directly proportional (is highly dependent) to the flow of the current in the wire. Therefore, one can easily manage, reverse, turn on or off, or vary the strength of a magnetic ?eld produced through the electric current.

The magnetic field can be envisioned as outlines of magnetic flux that create closed paths. You can refer to the below figure to visualize the diagram of a magnetic field (flux lines) formed around a wire carrying an electric current.

Working Principle of a Transformer

The concept of mutual induction does not end here. There's an additional interesting fact concerning electricity as well. Whenever a magnetic field changes across a coil of wire, it produces an electric current in the wire.

Therefore, it allows us to generate a fluctuating magnetic flux by passing an electric current in a wire or coil (where the electric current is also fluctuating).

Mutual Induction and Transformer

  1. An elementary transformer comprises dual coils that are electrically unconnected and inductive, but still both the winding coils are connected magnetically. The first coil, which passes through the electrical current generated from the source, is known as the primary winding, and the second coil, which provides the required output current, is called the secondary winding. The working principle of the transformer can be referred to in the diagram given below:
    Working Principle of a Transformer
  2. In the above diagram, you can see both the coils, i.e., the primary winding (the first coil of wire) and the secondary winding (the second coil of wire), are placed next to each other. Now, if pass a fluctuating current into the first coil, due to the phenomenon of electromagnetic induction, an electric current will be induced automatically in the second coil of wire. It occurs because the alternating current in the first coil creates an alternating flux, which is required for mutual induction between the two windings that induces a current in the second coil.
  3. All transformers operate in the same phenomenon. If the first coil conducts a sine-wave alternative current, then an induced sine-wave alternative current of the same frequency will be generated in the second coil of wire as well. The strength of the induced current also depends on the distance between the two wires.
  4. The entire setup is inserted inside a soft iron bar (known as core) to make the flow of electrical energy pass from the primary to secondary winding coil more efficiently.
  5. If the secondary winding coil carries the exact number of wires turns as present in the primary winding coil, the electric current induced in secondary will be effective of the equivalent magnitude as the primary coil. But if the number of wire turns in the secondary coil decreases or increases compared to the primary coil, the range of current and voltage generated in the second coil could increase or decrease than the first coil's current and voltage.
  6. One vital thing to note is that Transformers only work on the alternating current (frequently reversing or electricity) because a fluctuating flux is necessary for electromagnetic induction to occur between the two-wired coils. Hence, we can conclude that transformers do not work with direct current (DC), where a constant electric current is passed through the wire in the same direction.

Step-down transformer

If the primary winding has more number of turns than the secondary winding, the second coil's voltage is less than the primary coil's voltage. This process is known as a step-down transformer.

Step-up transformer

Transforming the above process can develop a step-up transformer that raises a lower voltage into a higher one. With a set-up transformer, the number of turns in the secondary winding is more when compared to the primary. Therefore, it has a higher secondary voltage and a shorter secondary electric current.

Transformer Construction

Working Principle of a Transformer


  • VPrepresents the Primary Voltage
  • VSrepresents the Secondary Voltage
  • NPrepresents the Number of Primary Windings
  • Ns represents the Number of Secondary Windings
  • Φ(phi)represents the Flux Linkage
  • T represents the time period to complete 1 cycle.

A transformer's fundamental construction is developed using two electric coil windings that carry mutual inductance and a laminated steel core. Both the coils (primary winding and the secondary winding) are insulated from one another and from the laminated core.

The transformer set-up also requires some appropriate containers for the constructed core and windings, a mode with which the core and electric coils can be easily insulated.

The major parts that every transformer contains are as follows:

1. Core

In all transformers, the core acts as a support to the winding. It is created out of transformer sheet steel laminations built to deliver a steady magnetic path with the slightest air-gap integrated and lower down the transformer loss.

The composition of a core is decided by factors, unlike effective voltage, current, power, etc. The diameter of the core is directly proportional (dependent) to copper losses and inversely proportional (inversely dependent) to iron losses.

2. Windings

Windings are defined as a set of copper wires coiled across the core. The copper wires are used in transformers because:

  • Copper is highly conductive in nature: It helps to reduce the loss in a transformer. Because the conductivity of the transformer increases, therefore the resistance of the current stream decreases.
  • Copper is high ductile in nature: This property states whether a metal can be cut down to very thin wires or not.

Primarily every transformer two types of windings, i.e., Primary windings and secondary windings, which are explained below:

  • Primary winding:The number of turns of windings in which the source current is provided.
  • Secondary winding:The set of turns of winding that induces the electromagnetic current and generates which output.

Both the windings are insulated from each other with the help of insulation coating instruments.

3. Insulation Agents

Insulation is an essential process of transformers as it helps to insulate windings from shorting the circuit and therefore easing the electromagnetic induction. Insulation mediators affect the robustness and the firmness of a transformer.

The various insulating agents used in a transformer are as follows:

  • Insulating oil
  • Insulating tape
  • Insulating paper
  • Wooden lamination

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