The direct-current machine is an electric machine which is easily adjustable in speed and torque thanks to power-electronic converters available today. The mechanical construction of a direct-current machine is depicted in Fig. 2.1 The stator is made up of the yoke and the main and auxiliary poles, bearing concentric windings. Most machines have several pairs of poles, so that the succession of ... [Show full abstract] main and auxiliary poles is repeated several times. In any case, the principle of operation of direct-current machines having one or more pairs of poles is, generally speaking, identical. The rotor (armature) have windings inserted in slots. The ends of the armature windings are connected to the collector; brushes are provided between the main poles in the neutral zone (NZ) for the armature terminals.