Transformer and its working principle

1. A transformer is an electrical device used to change the voltage levels in an AC circuit.
2. It operates on the principle of electromagnetic induction and mutual induction between two coils.

Working Principle of a Transformer

• Based on Faraday's laws of electromagnetic induction, a varying current in the primary coil produces a varying magnetic flux.
• This magnetic flux links to the secondary coil through a common core, inducing an EMF in the secondary coil.
• The transformer works only with AC (alternating current), as a constant DC current does not produce changing magnetic flux.
• The relationship between primary and secondary voltages is given by the formula:
  • V_s/V_p = N_s/N_p, where:
    • V_s: Voltage across the secondary coil.
    • V_p: Voltage across the primary coil.
    • N_s: Number of turns in the secondary coil.
    • N_p: Number of turns in the primary coil.
• The power input and output ideally satisfy the relation P_in = P_out (assuming no losses).

Types of Transformers

• Step-up Transformer: Increases voltage from the primary to the secondary coil (N_s > N_p).
• Step-down Transformer: Decreases voltage from the primary to the secondary coil (N_s < N_p).

Construction of a Transformer

• Consists of two windings: primary coil and secondary coil.
• The coils are wound on a magnetic core made of laminated sheets to reduce energy loss.
• Uses high-quality insulation to prevent short circuits.

Efficiency of a Transformer

• The efficiency of a transformer is defined as:
• Efficiency = (Output Power / Input Power) × 100%
• Real transformers are not 100% efficient due to energy losses.

Energy Losses in Transformers

• Core Loss (Hysteresis and Eddy Current Loss): Losses in the magnetic core due to alternating flux.
• Copper Loss: Heat loss due to resistance in the windings.
• Leakage Flux: Some magnetic flux does not link with the secondary coil.
• Dielectric Loss: Loss due to insulation resistance.

Applications of Transformers

• Power Transmission: Step-up transformers increase voltage for transmission, reducing energy loss.
• Power Distribution: Step-down transformers reduce voltage for safe household or industrial use.
• Electrical Devices: Used in chargers, adapters, and power supplies.
• Isolation Transformers: Provide electrical isolation between circuits for safety.
• Testing Equipment: Used in laboratories to test circuits at different voltage levels.

Conclusion

• A transformer is a crucial device in modern electrical systems, enabling efficient power transmission and distribution.
• Understanding its working and applications is essential for mastering concepts in electromagnetic induction and competitive exams.