The coils are made of copper bars and a coil of this coil is combined by two parts, which are welded together in the coil head. The insulation deublin bc-54065-24-50 of the coils is usually coating with “catalyzed” stage B mica-based tapes, having the same process in the stator. With a rheostat connected in series with the rotor, it is possible to regulate the current and the starting torque or in the regime conditions to vary the working rotation through the variation of the slip.
The coils are set rigidly within the grooves through wedges. The collector rings are supplied in stainless steel, however they can be supplied in brass or brass, depending on the application and in which electric motor will be installed. The rotor is short-circuited by intercession of the collector rings and brushes, which give access to the rotor winding, these are designed to withstand the required maximum operating current and the heat dissipation generated by the electric current and the contact between brushes and rings. Through the brushes and the collector it is permissible to connect a three-phase resistor in series with the rotor windings, thus varying the secondary impedance of the motor.