A Book Chapter of Basic Electrical and Electronics Engineering : Basic EEE

A transformer is a device that changes ac electric power at one voltage level to ac electric power at another voltage level through the action of a magnetic field. There are two or more stationary electric circuits that are coupled magnetically. It involves interchange of electric energy between two or more electric systems. Transformers provide much needed capability of changing the voltage and current levels easily. They are used to step-up generator voltage to an appropriate voltage level for power transfer. Stepping down the transmission voltage at various levels for distribution and power utilization. 1.   Transformer ClassificationIn terms of number of windings          Conventional transformer: two windings Autotransformer: one winding Others: more than two windings In terms of number of phases          Single-phase transformer           Three-phase transformer Depending on the voltage level at which the winding is operatedStep-up transformer: primary winding is a low voltage (LV) winding Step-down transformer: primary winding is a high voltage (HV) winding 2.   Primary and Secondary WindingsA two-winding transformer is shown below. It consists of two windings interlinked by a mutual magnetic field. Primary winding –energized by connecting it to an input source. Secondary winding –winding to which an electrical load is connected and from which output energy is drawn.