current is fed into the winding from an external exciter. Slots are also punched out along the circumference of the salient poles. They carry a squirrel-cage wind ing similar to that in a 3-phase induction motor. This damper winding serves to start the motor. Modern synchronous motors often employ brush less excitation, similar to that used in synchronous generators. Referring to Fig. 17.3, a relatively small 3-phase generator, called exciter and a 3-nhase recti fier are mounted at one end of the motor shaft. The dc current I from the rectifier is fed directly into the salient-pole windings without going through brushes and slip-rings. The current can be varied by controlling the small exciting current le that flows in the stationary field winding of the exciter. Fig. 17.4