Starting circuit for a synchronous machine having an electronic commutator

Claim 1

A starting circuit for a synchronous machine having an impressed d-c input and a commutator having at least two thyristors in the individual winding circuits of which the first thyristor is conducting and the second is not, said circuit comprising: at least one auxiliary circuit connected in parallel to the winding circuits comprising capacitance means an auxiliary voltage means removably connected to the capacitance means to charge the capacitance means, prior to the operation of the auxiliary circuit, to a voltage opposite to the conducting voltage of the semi-conductor rectifier in the individual winding circuits a rectifier circuit connected in series with the capacitor comprising an auxiliary control means having the same conducting polarity as the rectifiers in the windings, to conduct upon the triggering of the second of the controlled rectifiers in the winding circuits, and a diode of opposite polarity to the auxiliary thyristor, connected in parallel to the auxiliary thyristor, and control means to trigger the second thyristor and the auxiliary thyristor whereby the capacitance means discharges through the first thyristor and the auxiliary thyristor, thereby applying a negative voltage to the thyristor to cut off the first thyristor.