Synchronous machine can either be a synchronous generator or a synchronous motor. The following figure is a single phase model of a synchronous generator.
Ia1=Single phase armature current
Ra1 = Single phase equivalent armature winding resistance
Xa1 = Single phase equivalent armature winding inductance
Eg1 = Generated Voltage, which is a function of the field or excitation current
Vt = Line to neutral equivalent single phase terminal voltage
If1 = Excitation current
Rf1 = Excitation winding resistance
Vf1 = Excitation winding voltageFor a synchronous motor, the direction of the armature current will be just reversed while other parameters, including the field current, will still be the same.