A transformer is an electrical device that transfers electrical energy from one circuit to another circuit or multiple circuits. It is used to change the voltage level of an alternating current (AC) electrical energy. Specifically, a transformer that decreases the voltage is called a step-down transformer, whereas a transformer that increases the voltage is called a step-up transformer. A transformer can also provide galvanic isolation between circuits as well as couple stages of signal-processing circuits.

Transformers are used for various purposes, including:

• Power transmission: In electric power transmission, transformers allow transmission of electric power at high voltages, which reduces the loss due to heating of the wires. This allows generating plants to be located economically at a distance from electrical consumers.

• Voltage conversion: In many electronic devices, a transformer is used to convert voltage from the distribution wiring to convenient values for the circuit requirements, either directly at the power line frequency or through a switch mode power supply.

• Efficient power consumption: Transformers are employed to reduce the voltage of conventional power circuits to operate low-voltage devices, such as doorbells and toy electric trains, and to raise the voltage from electric generators so that electric power can be transmitted over long distances.

• Isolation: Isolation transformers are used to match the impedance of a source and that of its load, for most efficient transfer of energy. They are also employed to prevent a person from getting electrocuted and leakage current even if the electrical equipment connected to the output side causes insulation failure.

• Temporary power solutions: Portable transformers are designed to be lightweight and compact, making them easy to transport and set up in different locations as needed. They are used to reduce, increase, or clean existing voltage to provide electrical power to various equipment for different industry applications.

In summary, transformers are used to change the voltage level of AC electrical energy, and they have various applications in power transmission, voltage conversion, efficient power consumption, isolation, and temporary power solutions.