Single-Phase Transformer Fundamentals Explained

A single-phase transformer is a device that transfers electrical energy between two or more circuits through electromagnetic induction. It consists of two coils, known as the primary and secondary coils, wound around a common magnetic core. The primary coil is connected to the input voltage source, while the secondary coil is connected to the load.

Basic Principles of Single-Phase Transformer Operation

Faraday's Law of Electromagnetic Induction

When the primary coil is energized with an alternating current (AC), it creates a changing magnetic field around the coil. According to Faraday's Law of Electromagnetic Induction, this changing magnetic field induces an electromotive force (EMF) in the secondary coil. The induced voltage in the secondary coil depends on the turns ratio of the primary and secondary coils.

Single-Phase Transformer Construction

• Core

  The magnetic core is typically made of laminated iron or other magnetic materials to enhance the efficiency of energy transfer. It provides a low-reluctance path for the magnetic flux, reducing energy losses.

• Primary Coil

  Connected to the input voltage source, the primary coil receives the alternating current, generating a magnetic field in the core.

• Secondary Coil

  Connected to the load, the secondary coil experiences the changing magnetic field, inducing a voltage. The turns ratio (N1/N2) determines the voltage ratio between the primary (V1) and secondary (V2) coils (V2/V1 = N2/N1).

Single-Phase Transformer Operation

• Step-Up and Step-Down Transformation

  The turns ratio of the coils determines whether the transformer is a step-up or step-down transformer. If N2 (number of turns in secondary) is greater than N1 (number of turns in primary), it is a step-up transformer (V2 > V1). Conversely, if N2 is less than N1, it is a step-down transformer (V2 < V1).

• Magnetic Flux and Voltage Transformation

  The changing magnetic flux in the core induces a voltage in the secondary coil based on the turn ratio. This allows for efficient power transfer from the primary to the secondary circuit.

Ideal Single-Phase Transformer Equations

For an ideal transformer with no losses, the following relationships hold:

• Voltage Ratio: V1/V2 = N1/N2
• Current Ratio: I1/I2 = N2/N1

Efficiency and Losses in Transformers

In practice, transformers experience some energy losses. These primarily include:

• Resistive Losses (Copper Losses): Occur in the coils due to the resistance of the winding material.
• Eddy Current Losses: Occur in the magnetic core due to induced circulating currents.

These losses contribute to the transformer's overall efficiency, which is always less than 100% in real-world applications.