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.

Abstract: The invention is directed to an arrangement for detecting ground leaks and includes two identical synchronous machines coupled to the rotor of a brushlessly excited synchronous machine. One of the identical machines is built as an outer-pole machine and the other as an inner-pole machine. The stator winding of the outer-pole machine is supplied with a constant direct current and its rotor winding is connected through a rectifier bridge to be between ground and the neutral point of the rotor of the brushlessly excited synchronous machine. The rectifier feeds the rotor winding of the inner-pole machine, and the voltage measured at the stator winding of the latter is a measure of the insulation resistance in the rotor circuit of the brushless synchronous machine.