A power transformer is a stationary electrical device, and is a device for changing an AC voltage (current) of a certain value to another voltage or a voltage (current) of the same frequency.
Power transformers are one of the main equipments in power plants and substations. The role of transformers is not only to increase the voltage to send electricity to the electricity-consuming regions, but also to reduce the voltage to various levels of use voltage to meet the demand for electricity. In summary, step up and step down must be completed by transformers. In the process of power transmission in the power system, it will inevitably produce two parts of voltage and power loss. When the same power is transmitted, voltage loss is inversely proportional to voltage, power loss. It is inversely proportional to the square of the voltage. Using a transformer to increase the voltage reduces the transmission loss.