Abstract: An electric synchronous machine is excited via rotating rectifiers by an exciter machine. To this end, the three-phase winding of the exciter machine is connected to two Y-connected rectifiers having different current conduction directions. One end of the field winding of the synchronous machine is connected to the central point of the three-phase winding. In addition, there is provided between the Y-point of the rectifiers and the other end of the field winding one thyristor each, to the control electrodes of which a parallel-connected voltage sensitive firing device is coupled. Furthermore, stationary electrical elements are connected to the exciter device via switches and auxiliary slip rings and liftable brushes.