Section 14.7: Performance of a Round-Rotor Synchronous Motor
The synchronous motor is a synchronous generator in reverse (i.e., it consumes rather than produces electrical energy) and, as such, it has a (per-phase a) equivalent circuit as indicated below
The voltage and impedance are E and Zs = Ra + jXs respectively and usually Ra << Xs so Zs » jXs (Xs = synchronous reactance)
N.B.: Vt = Line-to-neutral terminal voltage