Working Principle of Transformer, Construction, Types and Applications

The transformer is one of the most important electrical machines used in power systems. It plays a vital role in transmission and distribution of electrical energy by stepping up or stepping down the voltage levels. In this article, we will learn about the working principle of transformer, construction, EMF equation, types, losses, and applications.

Working Principle of Transformer

The transformer works on the principle of electromagnetic induction and mutual induction. When an alternating current flows through the primary winding, it produces a changing magnetic flux in the core. This changing flux links with the secondary winding and induces an EMF (Electromotive Force) as per Faraday’s Law of Electromagnetic Induction.

Key Points:

Transformer works only with AC supply, not with DC.
No electrical connection between primary and secondary; only magnetic coupling exists.
Energy transfer is based on mutual induction.

Transformer Construction

A transformer mainly consists of the following parts:

Core: Made of laminated silicon steel sheets to reduce eddy current losses. Provides magnetic path.
Primary Winding: Connected to the input AC supply.
Secondary Winding: Connected to the output load.
Insulation: Provides electrical isolation between windings and core.
Tank: Protects the core and winding. Filled with insulating oil in case of large transformers.
Bushings: Provide insulated entry and exit for transformer terminals.

Core-Type Transformers

In core-type transformers, windings are placed around two limbs of the magnetic core. The core carries the major portion of the flux. It is simple in design and widely used for small and medium-size applications.

Shell-Type Transformers

In shell-type transformers, the core surrounds the windings. The flux has a double path, providing better efficiency and mechanical strength. These are commonly used for large power transformers.

EMF Equation of Transformer

The induced EMF in each winding of a transformer is given by:

E = 4.44 × f × N × Φm

E = RMS value of induced EMF
f = Frequency of AC supply (Hz)
N = Number of turns in winding
Φm = Maximum flux in core (Weber)

Voltage Transformation Ratio

The voltage transformation ratio (K) of a transformer is defined as:

K = V₂ / V₁ = N₂ / N₁

V₁ = Primary voltage
V₂ = Secondary voltage
N₁ = Primary turns
N₂ = Secondary turns

If K > 1 → Step-up transformer,
If K < 1 → Step-down transformer.

Losses in Transformer

The major losses in a transformer are:

Core Loss: Includes hysteresis and eddy current losses.
Copper Loss: I²R losses in primary and secondary windings.
Leakage Flux Loss: Due to imperfect magnetic coupling.
Dielectric Loss: Occurs in insulation (for high voltage transformers).

Types of Transformer

Transformers can be classified as:

Based on Function: Step-up, Step-down, Isolation Transformer.
Based on Construction: Core Type, Shell Type.
Based on Phases: Single-phase, Three-phase.
Based on Cooling: Air-cooled, Oil-cooled.
Special Types: Auto-transformer, Instrument Transformer (CT & PT).

Applications of Transformer

Used in power transmission and distribution to step-up or step-down voltage levels.
In electronic devices like chargers, adapters, and inverters.
Isolation transformers for safety in electrical circuits.
Used in measuring instruments (CT and PT).
HVDC and HVAC systems for efficient power transfer.

Conclusion

The transformer is the backbone of electrical power systems. From power plants to our homes, transformers are used everywhere. Understanding the working principle, EMF equation, losses, and types of transformer is very important for SSC JE, RRB JE, and other competitive exams.

FAQs on Transformer

Q1. On which principle does a transformer work?

Transformer works on the principle of mutual induction of two windings linked by a common magnetic flux.

Q2. Can a transformer work on DC supply?

No, transformers cannot work on DC supply because EMF is induced only due to changing magnetic flux (AC source).

Q3. What is the efficiency of an ideal transformer?

The efficiency of an ideal transformer is 100% because there are no losses.

Q4. What are the two main types of transformers based on construction?

The two main types are Core Type Transformer and Shell Type Transformer.

Working Principle of Transformer, Construction, Types and Applications

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