Direct current finds use in many industrial sectors, such as in electrochemical installations, battery packs, electric traction, electromagnets for industrial applications, electric arc welding, etc. In electrochemical installations, direct current is achieved by rectifying the alternating current through tunga, selenium or silicon rectifiers ami here, but in many installations of this type the direct current is caused by dynamos, that is, by machines that generate energy electric current using mechanical energy that is produced by thermal motors or by asynchronous motors.

The operating base of the dynamos is the same as that of the alternators, that is, for a coil to generate a f.e. she must undergo a flow of flow. If a coil rotates in a magnetic field, the flux variations of the north pole and the south pole follow in rotation, generating in the coil a f.e. alternating sinusoidal. It is evidenced that it is impossible to generate f.e. directly through coils that rotate in a magnetic field. To correct f.e.m. alternating in the dynamos of the dynamos, uses the collector formed by sheets of copper isolated from each other, also called commutator.