What is a Transformer ? Krish Advani 12/12/2012 Engineering A transformer is a static device which is used to transfer electrical energy from one ac circuit to another ac circuit, with increase or decrease in voltage and current but without any change in the frequency. It is important to remember that the input to a transformer and output to a transformer both are alternating quantities (AC). Electrical energy is generated and transmitted at extremely high voltages. The voltages need to be reduced to a lower value for its domestic and industrial applications. This process is done using a step down transformer. The function of step down transformer is to reduce the voltage and current of the supplied voltage without changing its frequency. On the other hand, we can also use transformer to increase the voltage levels. This is done by using a step up transformer. TWO WINDING TRANSFORMER Transformers are used in power supplies, mains transformer, etc… A transformer plays an important role in our life. Even to charge our mobile phone a transformer in required.