NOVELTY - The rotor (6) has a rotor body (10) rotating about a rotation axis (R), and winding elements (14) arranged in grooves (13). Two winding heads are arranged above and below the rotor body in an axial direction, and a winding head carrier (15) for carrying the winding heads is arranged radially within the winding heads. The carrier is fixed indirectly on the rotor body, or on a component revolving with the rotor body. Spring elements (19) are provided in a fastening region and act in the axial direction against a gravitational force (g) between the rotor body, the component and the carrier.    USE - Rotor i.e. slip-ring rotor, for a dynamo-electric machine i.e. variable rotation speed, double-fed asynchronous machine, that is utilized in a machine set as a hydropower motor for pumping water to a higher level and as generator for generating electricity from hydro energy in a hydroelectric power plant (all claimed) i.e. pump-storage hydroelectric power station.    ADVANTAGE - The spring elements are provided in the fastening region and act in the axial direction against the gravitational force between the rotor body, the revolving component and the winding head carrier, thus preventing unnecessary mechanical load of the winding elements caused by thermal expansion of the winding elements on the winding head carrier in the axial direction, and hence enabling problem-free and reliable operation of the rotor for a long time. The rotor operates large machines with electrical capacity of 30 megavolt-amperes.    DETAILED DESCRIPTION - The spring elements are designed as cup springs, spiral springs or elastomer springs. An INDEPENDENT CLAIM is also included for a machine set for a hydroelectric power plant.    DESCRIPTION OF DRAWING(S) - The drawing shows a partial sectional view of a winding head of a rotor.    Gravitational force (g)    Rotation axis (R)    Rotor (6)    Rotor body (10)    Grooves (13)    Winding elements (14)    Winding head carrier (15)    Spring elements (19)