The moment an electric current passes through a conductor, a magnetic field is caused around it. The main concepts about magnetism that must be considered is that as an extremely important part of electricity, since in addition to the motors, the electromagnets are used in numerous electrical components. This type of engine has a simplified construction and a significantly reduced cost, as well as being very versatile and non-polluting. During its technological development, the electric motor has become one of the most relevant projections of man.
Its purpose is basically the drive of machines, mechanical equipment and appliances, among others, no less important. Its fundamental principles of operation, construction and methods of departure must be analyzed and respected in order to ensure satisfactory application. It can be affirmed that the electric machines are completely commanded by means of keys of departure, being that the most used consist of the direct or reversing, that has as function to drive small motors; the start star triangle, which acts in the drive of large motors without load; the compensating start, able to drive large motors with load; the start with soft-starter, used to connect large motors with load; and the starter with frequency inverter, used for small and large motors.