In electric motors the three-phase circuit is composed of three alternating voltages, in which the electric energy is transmitted by means of the composition of the three voltage signals lagged 120º of a cycle with each other.
In the early days of the implementation of the long-distance power transmission system, thanks to the technological advancement mainly due to the work of Nikola Tesla, the alternating system for voltages and currents was used in order to allow the transport of energy over long distances without losses To the point of making the process unfeasible.
For the generation of alternating voltages and currents, synchronous generators or MIT motors are used, which in theory could provide any number of alternating voltage and current signals, equally lagged depending on the generator construction.
For reasons of practicality, economics (material economy) and techniques (quality of energy supplied), it was decided to use the three-phase system.
The advantages of the three-phase system over the single phase are:
– For the same size, three-phase generators and motors are more powerful than single-phase motors;
– Three-phase transmission lines require less copper than single-phase transmission lines to carry the same power.