The armature winding of a synchronous machine is usually on the stator,andFig.14-1.The field winding is excited by an external DC supply. The direct current is connected to the rotor winding by means of a pair of stationary carbon brushes which contact rotating slip rings. It is advantageous to have the single,low-power field winding on the rotor while having the high-power multiple-phase armature winding on the stator.