Electric motors belong to two large groups of direct current and alternating current. Electric induction motors fit into asynchronous AC motors precisely because they can not operate at synchronous speed. About 80% of the energy consumed by the industries is used to convert electrical energy into mechanics through electric motors.

The electric motors of direct current have this name because they are constant in the time, having its value well defined, circulating in the same direction in a conductor. Alternate current motors are unstable in time, alternating the direction they circulate in a conductor. Alternating current is used in many applications, especially in large power systems, industries and home environments, usually in motors that equip appliances such as electric kettles, refrigerators and washing machines best offers for baldor.

All electronic circuits are powered by an electric power source and usually this source is a DC voltage source. For portable systems batteries can be used, however, the circuits need to be powered from the alternate local power grid available. For these cases, there should be a part of the equipment that converts the alternating waveform of the network to direct current.