### 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.