The motors are solidly designed and are maintenance-free for life. The multi-grooved stator contains a threefold winding which, together with the phase-shifting capacitor (series KD), creates a symmetrical rotating field at the rated working point of the motor. The rotor is of the squirrel-cage type. Two design diameters and a variety of design lengths provide rated torques from 0.75 to 31.5 Ncm in double-pole or four-pole versions.