Transformer Basic operational principle

Working Principle of Transformer: Principle, Operation & Construction

Introduction

A transformer is one of the most important electrical machines used for transferring electrical energy from one circuit to another at the same frequency but with different voltage levels. It works on the principle of Faraday’s Law of Electromagnetic Induction and uses mutual induction between its windings.

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Faraday’s Law of Electromagnetic Induction

According to Faraday’s law:

“The rate of change of magnetic flux linkage with respect to time is directly proportional to the induced EMF in a conductor or coil.”

 

This means whenever a conductor or coil experiences a changing magnetic field, an electromotive force (EMF) is induced in it.

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Fundamental Principle of Transformer

The basic working of a transformer can be understood in simple steps:

1. Alternating supply to primary winding

   • When an AC voltage is applied to the primary winding, alternating current flows through it.

   • This produces an alternating magnetic flux around the coil.

2. Magnetic flux linkage

   • If a secondary winding is placed near the primary, part of this alternating flux links with the secondary coil.

3. EMF induction in secondary winding

   • Due to the changing flux linkage, an EMF is induced in the secondary winding (as per Faraday’s law).

   • If the secondary circuit is closed, current flows through it, delivering power to the load.

👉 This is the simplest explanation of transformer action.

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Why Core is Needed?

In open air, only a small fraction of flux from the primary winding links with the secondary, resulting in negligible induced current. To solve this, a low-reluctance magnetic core is used.

• The core provides a common magnetic path for both windings.

• This ensures maximum flux linkage, improving efficiency.

Thus, the core is an essential part of a practical transformer.

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Construction of Transformer

A transformer mainly consists of three key components:

1. Magnetic Core

   • Provides a closed path for magnetic flux.

   • Made of laminated soft iron or silicon steel to reduce eddy current losses.

2. Primary Winding

   • Connected to the input AC supply.

   • Produces alternating magnetic flux in the core.

3. Secondary Winding

   • Linked with the magnetic flux of the core.

   • Delivers transformed voltage to the load.

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Summary of Working Rule

• A transformer works on AC supply only (not DC).

• Primary winding → generates alternating flux.

• Core → provides flux linkage path.

• Secondary winding → receives induced EMF and supplies load.

This entire operation is governed by Faraday’s law of electromagnetic induction and mutual induction between windings.

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✅ In short:
Transformer transfers electrical energy between two circuits using mutual induction, without changing frequency but with a change in voltage level.

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