Patent for a new and useful improvement in a dynamo-electric machine to provide a rotor in which certain coils of the winding are automatically cut out and utilized as open coils to prevent the turns in those coils from having a demagnetizing action. Another objective is to provide a rotor whose core consists of non-magnetic material to refuce the inductance and self-induction of the winding and the sparking at the commutator due to the shifting of the magnetic field and the neutral or point of commutation.