The rotor for a dynamo electric machine serving as a synchronous generator as well as being designed operable as a variable speed motor for starting a prime mover for the synchronous generator, the rotor (1) comprising a rotor core (2), a plurality of slots (4) disposed around the circumference of the rotor core (2) and extending along the axial direction of the rotor core (2), rotor windings (3) being accommodated in the slots (4) and wedges (6) being accommodated in the slots (4) over the rotor windings (3) near at the surface of the rotor core (2) for preventing the rotor windings (3) from being pushed out due to a centrifugal force caused by rotation of the rotor (1), wherein wedges (6) where an eddy current flows are formed by Cu-0.05.about.4 wt % Zr-0.3.about.5 wt % Ni-0.2.about.1.5 wt % Si having a 0.2% proof stress equal to or more than about 20 Kg/mm.sup.2 and an electrical conductivity equal to or more than about 20% IACS (International Annealed Copper Standard), whereby damages of the rotor elements due to electrolytic corrosion are prevented.