This is what the magnetic flux would look like for a four pole rotor. When an armature coil is wrapped around a rotor the moving magnetic flux creates an alternating electromagnetic force in the coil The electrons inside the material are disturbed by the magnetic field and are forced to move in an alternating direction.

   The displacement of the electrons during a rotation can be plotted in a graph. this creates a sine wave pattern hence the name, alternating current. By adding two more armature coils on a 120 degree angle a three-phase current can be generated. This is generally used for transporting electric power the speed of the alternating magnetic flux defines the frequency of the current. So adding more poles and more rpm creates a higher electric frequency.

   Now let's consider that the armature coils are connected to the three-phase current of a grid This 50 Hertz three-phase alternating current actually creates a rotating magnetic field like this The magnetic field of the rotor locks on to this magnetic field In a synchronous generator the rotor follows the frequency of the grid You can compare the grid with a steady moving heavy train You can push against it, but it won't actually move faster.

   You're bound to the speed of the train And how do you board a moving train? In a four pole rotor that is connected to the grid the shaft will have to turn 1500 rpm gearbox motor generator for wind turbine use gearboxes to increase the frequency of the rotor shaft direct drive turbines use more poles.