The alternating current is constantly changing, and how is the ac motor going to be controlled?
Three phase motor changes phase sequence. A one-way motor changes the main winding or the secondary winding in the direction of the line.
Ac motor direction of rotation is not determined by the alternating current (ac) plus or minus half cycle of direction, but by the alternating current (ac) through a certain way of dealing with the rotating magnetic field generated by acting on the rotor, just like you with a permanent magnet circle around the compass makes a compass as the principle of spin the rotor rotation, its rotation direction depending on the direction of the rotating magnetic field.
There are many methods of rotating magnetic field, such as three-phase winding, single-phase shift phase, short circuit, pulse changing phase, etc.
