Converter-powered drive for an elevator

Claim 1

A converter-powered drive for an elevator and connected to an a.c.-voltage source, comprising: a d.c.-electro-motor containing an armature connected in an armature circuit; a converter defining only one direction of current flow and containing a predetermined number of thyristors; said armature being connected to said a.c.-voltage source via said converter; said converter possessing a d.c.-negative pole and a d.c.-positive pole; a switching circuit for torque reversal and connected between said converter and said armature; said switching circuit comprising four thyristors which contain related cathodes; two of said four thyristors being connected between said d.c.-negative pole of said converter and said armature and two further thyristors of said four thyristors being connected between said d.c.-positive pole of said converter and said armature; an extinguishing circuit operatively associated with said switching circuit; said extinguishing circuit at least containing a capacitor, an inductor, a resistor, and a thyristor possessing a cathode; said extinguishing circuit, upon the occurrence of excess current, protecting said thyristors of said converter and said resistor of said extinguishing circuit dissipating the energy appearing in said armature circuit; said converter constituting a twelve-pulse converter comprising two series-connected twin star connections; said thyristor and said resistor of said extinguishing circuit forming a series-connection having two terminals; each terminal of said series-connection being connected to said armature via two related diodes; said extinguishing circuit further containing a current transformer which is arranged in said armature circuit and which causes ignition of said thyristor of said extinguishing circuit upon the occurrence of said excess current; said capacitor of said extinguishing circuit being connected to said cathode of said thyristor in said extinguishing circuit and to said cathodes of said two of said fourth thyristors in said switching circuit which are connected between said d.c.-negative pole of said converter and said armature; one of said two thyristors being extinguished upon the occurrence of said excess current and upon ignition of said thyristor in said extinguishing circuit, whereby said converter is disconnected from said d.c.-electro-motor; said switching circuit further containing two voltage converters; one of said two voltage converters being connected to said d.c.-negative pole and said d.c.-positive pole of said converter, and an other one of said two voltage converters being connected with said armature; one pair of said four thyristors in said switching circuit constituting a current conducting pair of thyristors, and an other pair of said fourth thyristors in said switching circuit constituting a non-current conducting pair of thyristors; and said two voltage converters serving to generate, as a result of a voltage difference existing during a zero-crossing of the current flowing through said pair of current conducting thyristors, a control signal controlling the ignition of said other pair of non-current conducting thyristors.