In the case of a synchronous generator, three balanced emf's of frequency f=Pn/120Hz
are induced in the three phase windings when the rotor is driven by a prime mover rotating
at a speed n. If the three phase stator circuit is closed by a balanced three phase electrical load, balanced three phase currents of frequency f will flow in the stator circuit, and these currents will generate a rotating magnetic field of a speed nf = 120f/P = n.