Smooth poles synchronous electric motors have the rotor squirrel cage installed in specific grooves in the rotor plate package, all around its perimeter and symmetrically distributed at the periphery of the rotor. https://www.mrosupply.com/v-belts/v-belts/b-section/178336_b116_gates-rubber/ The segments of the cage at each pole are connected to each other forming the complete short-circuit rings and consequently the complete rotor cage of this type of electric machine. In such a rotor configuration, the bars of the short-circuit cage are not symmetrically arranged at the periphery of the rotor, thus having concentration of bars in the regions of the poles and absence of bars.
This cage is characteristically made of copper or brass, depending on the characteristics and starting specificities of the machine. The bars are arranged symmetrically at the periphery of the rotor plate package and shorted at the ends of the package through end plates or rings, thus forming the cage. The size of the cage adapts the smooth torque curve and lower pulsating torque during the start. The synchronous electric motors of rolled protruding poles have the rotor squirrel cage bars housed in the pole shoes and shorted at the ends through segments of the shortcircuit rings, thereby forming, at each pole, a segment of the complete cage.