Abstract: An excitation system for a synchronous machine comprising an exciter having its output connected through a current relay in parallel with a starting-protecting unit. The starting-protecting unit includes parallel branches, each comprising a series-connected resistor and thyristor switch having a voltage-sensitive threshold element connected between its anode and gate. A turn-on unit for the parallel branches of the starting-protecting unit includes a voltage-sensitive overvoltage detector connected in parallel with the exciter output, in which the voltage setting is lower than that of the threshold element of the parallel branches of the starting-protecting unit. A memory unit; and a pulse-forming unit. The output of the overvoltage detector is connected through the memory unit to the input of the pulse-forming unit. The output of the pulse-forming unit is connected via the contacts of the current relay to the gates of the thyristor switches in the parallel branches of the starting-protecting unit.

Abstract: A device for exciting a synchronous machine, comprises an exciter electrically connected to an exciting winding of the synchronous machine, a starting unit connected in parallel with the exciter and comprising at least one branch having a resistor and a thyristor switch placed in series. The control circuit of the thyristor switch has a threshold element. A protective thyristor is placed parallel to the branch of the starting unit and its control electrode is connected via the commutator of a current sensor of the starting unit branch to the control circuit of the protective thyristor. A safety device is inserted in series into the starting unit branch circuit.