Transformer

Transformer

A transformer is a passive electrical device that transfers electrical energy between two or more circuits through electromagnetic induction. Transformers are used to increase or decrease the alternating voltages in electric power applications.

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Power supply transformer

Basic Principles

Transformers operate on the principle of Faraday's law of induction, which states that a change in the magnetic field within a closed loop induces an electromotive force (EMF) in the wire. A transformer consists of two or more wire coils called windings, which are wound around a common core. When an alternating current (AC) flows through the primary winding, it creates a varying magnetic field in the core, which induces a voltage in the secondary winding.

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Iron core of a transformer

Core

The core of a transformer is typically made of laminated silicon steel to reduce eddy current losses. The core provides a low reluctance path for the magnetic flux, which is essential for efficient operation.

Types of Transformers

Transformers can be classified into several types based on their construction, application, and function.

Power Transformers

Power transformers are used in transmission networks to step up (increase) or step down (decrease) the voltage levels. They are designed to operate at high efficiency and are typically used in power generation and distribution systems.

Distribution Transformers

Distribution transformers are used to provide the final voltage transformation in the electric power distribution system, stepping down the voltage used in the distribution lines to the level used by the customer.

Instrument Transformers

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Instrument transformer terminals

Instrument transformers are used to measure high voltages and currents in power systems. They include current transformers (CTs) and voltage transformers (VTs), which provide a scaled-down replica of the current or voltage for measurement and protection purposes.

Operation Under Load

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Transformer under load

When a transformer is under load, the secondary winding delivers power to the load, and the primary winding draws power from the source. The efficiency of a transformer is determined by the ratio of the output power to the input power.

Equivalent Circuit

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Equivalent circuit of a transformer

The equivalent circuit of a transformer is a simplified representation that models the electrical characteristics of the transformer, including the winding resistances, leakage reactances, and core losses.

Magnetic Flux

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Magnetic flux in a transformer

The magnetic flux in a transformer is confined to the core and is responsible for the induction of voltage in the windings. The flux linkage between the primary and secondary windings is crucial for the transformer's operation.

Over-Excitation

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Over-excitation in a power transformer

Over-excitation occurs when the voltage applied to the transformer exceeds its rated voltage, causing excessive magnetic flux in the core. This can lead to overheating and damage to the transformer.

3D Model

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3D model of a transformer

A 3D model of a transformer provides a visual representation of its components, including the core, windings, and terminals.

Related Pages

• Electromagnetic induction
• Electric power distribution
• Voltage regulation
• Electrical engineering