What is a Transformer? A Transformer is a static electrical machine which transfers AC electrical power from one circuit to the other circuit at the constant frequency, but the voltage level can be altered that means voltage can be increased or decreased according to the requirement. It works on the principle of Faraday's Law of Electromagnetic Induction which states that, "the magnitude of voltage is directly proportional to the rate of change of flux." Usually, electrical power is generated at 11 kV. For economical reasons AC power is transmitted at very high voltages say 220 kV or 440 kV over long distances. Therefore a step-up transformer is applied at the generating stations. Now for safety reasons the voltage is stepped down to different levels by step down transformer at various substations to feed the power to the different locations and thus the utilisation of power is done at 400/230 V. It's construction mainly consists of: Magnetic circuit (consisting of core, limbs, yoke and damping structure) Electrical circuit (consisting of primary and secondary windings) Dielectric circuit (consisting of insulations in different forms and used at different places) Tanks and accessories (conservator, breather, bushings, cooling tubes, etc.)