As for the electric currents, in case the current is momentarily alternated, the field H will also be, being that the value at each moment will be solved by the same values, being able to reverse the direction every half cycle.
Thus, in the event of a coil being crossed by an electric current, a magnetic field will be caused, which will be oriented entirely according to the axis of the coil and the value proportional to the current. If it is a single-phase winding, it will be covered by a specific current.
Thus, the winding consists of a pair of poles, being a north pole and a south pole, in which the effects are added to establish the field H. Consequently, the field ends up becoming pulsating, since in the its intensity varies proportionally to the current, always in the same north-south direction.
In the case of a three-phase winding, made by three 120-degree spaced single-phase windings, it is fed by means of a three-phase system, the currents I1, I2 and I3 will likewise create their own magnetic fields H1, H2 and H3 . These fields are moved 120 degrees apart.