Abstract

Transformers are electrical devices that change or transform voltage levels between two circuits. In the process, current values are also transformed. However, the power transferred between the circuits is unchanged, except for a typically small loss that occurs in the process. This transfer only occurs when alternating current (a.c.) or transient electrical conditions are present. Transformer operation is based on the principle of induction, formulated by Faraday in 1831. He found that when a changing magnetic flux links a circuit, a voltage or electro-motive force (emf) is induced in the circuit. The induced voltage is proportional to the number of turns linked by the changing flux. Thus, when two circuits are linked by a common flux and there are different linked turns in the two circuits, there will be different voltages induced. This situation is shown in Figure 1.1 where an iron core is shown carrying the common flux. The induced voltages V₁ and V₂ will differ since the linked turns N₁ and N₂ differ.