Working Principle and Types of Transformers

Mukesh Yadav
3 min readMay 31, 2022


Transformers transmit electric energy from one alternating current circuit to another by increasing or decreasing the voltage. From toy trains to power grids, there are many applications of a transformer. Let’s look at the types of transformers, and their working in more detail.

Working Principle of Transformer

A transformer’s operation is straightforward. It works on the principle that mutual induction allows the transfer of electrical energy across circuits using two or more coils.

The image depicts the primary and secondary coils of an electrical transformer. The core is laminated with strips that have thin gaps in between them, which run across the cross-section of the core. The transformer generates an electromotive force from the alternating flux set up in the laminated core due to the coil that connects to a source of alternating voltage (primary coil). The primary coil is linked to the secondary coil, which in turn, produces a mutual induced electromotive force. With the help of Faraday’s laws of Electromagnetic Induction, this electromotive force is written as:


After closing the second coil circuit, current passes through it and electrical energy magnetically transfers from the first to the second coil. As the first coil receives an alternating current source, we refer to it as the primary winding. On the other hand, because energy is extracted from the second coil, it is called the secondary winding.

In summary, a transformer performs the following operations:

  • Transfers electric power from one circuit to another.
  • Transfers electricity without any change in frequency.
  • Uses the electromagnetic induction method to transfer electricity.
  • Links the two electrical circuits with mutual induction.

For a better understanding of the working principle of a transformer, you may watch the video linked below.

Working of a Transformer

Components of a Transformer

A transformer’s primary components are as follows:


The core of the transformer functions as a support for the winding. It also provides a low resistance channel for the flow of magnetic flux. To decrease energy losses, a core consists of a laminated soft iron core. Furthermore, parameters such as operational voltage, current, and power determine the core composition. A point to note is that the core diameter is related to the amount of copper lost and inversely proportional to the amount of iron lost. (For more information, read the FAQs)

The Winding

Windings are the copper wires that coil around the transformer core. The high conductivity of copper minimizes the loss of energy because of the principle: “when the conductivity increases, resistance to current flow decreases”. Furthermore, the high ductility of copper, which allows for the metal to be moulded into thin wires, is a desirable trait as well.

Windings are classified into two categories.

  • Primary Winding: These are the set of coils that obtain supply current.
  • Secondary winding: These are the set of coils that release the current output.


Transformers require insulation to separate windings as well as prevent short circuits. Therefore, insulating agents have an impact on a transformer’s durability and stability. A transformer employs the following materials as an insulating medium:

  • Oil
  • Tape
  • Wood-based lamination

Types of Transformers: Based on Design

The arrangement of the main and secondary coils around the laminated steel core varies across transformer types. This gives rise to two types of transformers based on their design:

Core Transformers

In this transformer, windings coil around a large portion of the core. These coils are form-wound and cylindrical in shape. On the other hand, the core is rectangular. Additionally, the circular or cylindrical coils are such that they fit over a cruciform section of the core.

Circular cylindrical coils provide a significant advantage in terms of mechanical strength. These coils consist of multiple layers, each of which may be insulated from the others using materials such as paper, cloth, micarta board, and so on. The image below depicts the typical configuration of the core-type transformer with regard to the core.

Originally posted on transformers!