Transformers

Concepts to remember about Transformers for JEE and CBSE board exams:

Basic Concepts:

Transformer: A device that transfers electrical energy from one circuit to another through electromagnetic induction. Core: Made of laminated iron to reduce eddy currents. Windings: Primary winding (connected to the AC source) and secondary winding (delivers power to the load). Insulation: Prevents electrical contact between windings. Principle of Operation: Based on Faraday’s Law of Electromagnetic Induction.

EMF Equation:

Vp/Vs = Np/Ns Voltage transformation ratio equals turns ratio.

Turns Ratio:

Np/Ns Ratio of the number of turns in the primary winding to the number of turns in the secondary winding.

Ideal Transformer:

Assumptions: Perfect magnetic coupling (no leakage flux) and 100% efficiency. Voltage Transformation Ratio: Vp/Vs = Np/Ns. Current Transformation Ratio: Ip/Is = Ns/Np. Power Transformation: Pp = Ps.

Practical Transformer:

Losses: Copper loss (due to resistance of windings), hysteresis loss (due to magnetization and demagnetization of the core), and eddy current loss (due to induced currents in the core). Efficiency: Less than 100% due to losses. Transformer Testing: Open-circuit test and short-circuit test to determine parameters.

Types of Transformers:

Power Transformer: Used for power distribution. Distribution Transformer: Steps down voltage for local distribution. Autotransformer: A transformer with a single winding that acts as both primary and secondary. Step-Up Transformer: Increases voltage. Step-Down Transformer: Decreases voltage. Isolation Transformer: Provides isolation between two circuits.

Special Transformers:

Three-Phase Transformer: Used in three-phase power systems. Instrument Transformer: Current transformer or potential transformer used for measurement purposes. Scott Connection: Used to obtain two-phase power from a three-phase supply. Polyphase Transformer Connections: Star and delta connections for polyphase systems.