Table of Contents 1 Introduction 3 1.1 Working Principle 3 1.1.1 Mutual Inductance 3 1.1.2 Ideal Transformer 3 1.1.3 Real Transformer 3 1.2 Main Types 3 1.2.1 Step-up Transformer 3 1.2.2 Step-down Transformer 3 1.3 Transformer Ratios 3 1.3.1 Turn Ratio 3 1.3.2 Voltage Ratio 3 1.3.3 Power Ratio 3 1.4 Uses and Applications 3 2 History of Transformer 3 2.1 A.C or D.C 3 2.2 Need of Transformer 3 2.3 Invention of Transformer 3 2.4 First Commercial Use 3 2.5 Transformer Development Timeline [13] 3 1830s 3 1836 3 1876 3 1878 -1883 3 1881 3 1880-1882 3 1882 - 3 1884 3 1884 3 1885 3 1885 3 1886 3 Later 1880s 3 1889 3 1891 3 1891 3 1880s - Today 3 3 Working of Transformer 3 3.1 Construction 3 3.1.1 Core Construction 3 3.1.2 Winding Arrangements 3 3.2 Working 3 4 Types of Transformer 3 4.1 On the Basis of Construction 3 4.1.1 Core Type Transformer 3 4.1.2 Shell Type Transformer 4 4.2 On the Basis Their Purpose 5 4.2.1 Step up Transformer 5 4.2.2 Step down Transformer 6 On the Basis of Type of Supply 7 References: 8

1 Introduction
A transformer is an electrical device that transfers electrical energy from one circuit to another circuit using inductively coupled conductors. In other words by putting two coils of wire close together while not touching, the magnetic field from the first coil called the primary winding effects the other coil (called the secondary coil). This effect is called "inductance". [12]
1.1 Working Principle
Transformer works on the principle of mutual induction of two coils. When current in the primary coil is changed the flux linked to the secondary coil also changes. Consequently an EMF is induced in the secondary coil. [2] 1.1.1 Mutual Inductance
The phenomenon in which a changing current in one coils induces current in another coil is called