Electric motor is an electrical device that converts electrical current or energy into mechanical rotational energy. The reverse of this is the conversion of mechanical energy into electrical energy and is done by an electric generator. Electrical motors can be powered by direct current (DC) such as batteries, motor vehicles or rectifiers or by alternating current (AC) sources, such as from the power grid, inverters or generators. There are many different types of motor equipment, including standard motors, variable speed rated, motors with built-in gearboxes, and servo motors