Synchronous Machines

Alternators generate almost all grid power. A DC-excited rotor (or permanent magnets) spins at $N_s = 120f/P$:

• Cylindrical (round) rotor — 2 or 4 poles, high speed, steam and gas turbines (3000 rpm at 50 Hz).
• Salient pole — many poles, low speed, hydro turbines.

EMF equation: $E = 4.44\, k_w\, f\, \Phi\, N_{ph}$.

A synchronous motor is not self-starting (it uses damper windings or a VFD). By changing its field excitation it can operate at lagging, unity or leading power factor; an over-excited unloaded synchronous motor is a synchronous condenser for reactive power support.