Construction of a Transformer

A transformer is a static electrical device that transfers electrical energy between circuits through electromagnetic induction. It consists of the following key components:

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1. Core

Made of laminated silicon steel sheets to reduce eddy current losses.

Provides a low-reluctance path for magnetic flux.

Can be core-type or shell-type based on winding arrangement.

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2. Windings

Primary Winding: Receives input AC voltage.

Secondary Winding: Delivers transformed voltage output.

Made of copper or aluminum for efficient conduction.

Windings are insulated to prevent short circuits.

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3. Insulation Materials

Oil-impregnated paper, varnish, or epoxy resin insulates windings.

Transformer oil (in oil-filled transformers) insulates and cools components.

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4. Transformer Oil (For Oil-Immersed Transformers)

Acts as an insulator and coolant.

Dissolved Gas Analysis (DGA) monitors transformer health.

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5. Conservator Tank

Present in large oil-filled transformers.

Allows oil expansion and prevents oxidation by keeping the oil away from air.

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6. Buchholz Relay

A protective device placed between the main tank and conservator.

Detects gas accumulation due to insulation failure or internal faults.

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7. Cooling System

Air Natural (AN): Uses ambient air for cooling.

Oil Natural Air Natural (ONAN): Uses oil circulation with natural air cooling.

Oil Natural Air Forced (ONAF): Uses oil circulation with forced air cooling via fans.

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8. Tap Changer (For Voltage Regulation)

On-Load Tap Changer (OLTC): Adjusts voltage without interrupting the load.

Off-Load Tap Changer: Requires power shutdown to adjust taps.

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9. Tank and Bushings

Tank: Encloses the transformer, protecting internal components.

Bushings: Provide insulated passage for electrical connections.

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Types of Transformer Construction

1. Core Type Transformer: Windings surround the core limbs.

2. Shell Type Transformer: The core surrounds the windings for better magnetic flux containment.

3. Toroidal Transformer: Core is ring-shaped with windings wrapped around it, reducing leakage flux and improving efficiency.