Abstract A current chopper for DC machines connected to the terminals of a source having an inductive impedance such as a traction powerline. The chopper comprises a filter connected between the source and the switching devices of the chopper, a power dissipating circuit connected in parallel with the main circuit and located between the filter and the above-mentioned switching devices of the chopper. The power dissipating circuit is connected and disconnected from the circuit by means of a switching device connected in series with the power dissipating circuit. The chopper further comprises a control and protection logic device controlling the operation of the chopper by detecting the abnormal operations thereof such as overcurrents and overvoltages, and by causing their cancellation by limiting the overvoltages resulting therefrom, in normal operation, by decreasing the current in accordance with a predetermined law and, in abnormal operation, by instantaneously blocking the chopper and simultaneously inserting across the source of power dissipating circuit.
A current chopper for DC machines connected to the terminals of a source having an inductive impedance, comprising: a. a filter connected between the source and the switching devices of the chopper, said filter including a capacitor connected across the source for limiting the amplitude of the overvoltages at the terminals of the switching devices of the chopper, b. a power dissipation device connected in series with a switching device across the source and located between said filter and the switching devices of the chopper, said power dissipating circuit being connected to and disconnected from the source by means of said switching device, and c. a control and protection logic circuit controlling the operation of the chopper by detecting its abnormal states of operation due to overcurrents and overvoltages and causing the cancellation thereof by limiting the overvoltages resulting therefrom either, in normal operation, by decreasing the output current of the chopper in accordance with a predetermined law, or during abnormal conditions causing overvoltages across the capacitor of the filter, by the insertion of said power dissipating circuit in place thereof, thereby permitting the use of a filter of smaller dimensions.
Claim 2
Dependent Claim
191 words
A current chopper for DC machines connected to the terminals of a source having an inductive impedance, comprising: a. a filter connected between the source and the switching devices of the chopper, said filter including a capacitor connected across the source for limiting the amplitude of the overvoltages at the terminals of the switching devices of the chopper, b. a power dissipation device connected in series with a switching device across the source and located between said filter and the switching devices of the chopper, said power dissipating circuit being connected to and disconnected from the source by means of said switching device, and c. a control and protection logic circuit controlling the operation of the chopper by detecting its abnormal states of operation due to overcurrents and overvoltages and causing the cancellation thereof by limiting the overvoltages resulting therefrom either, in normal operation, by decreasing the output current of the chopper in accordance with a predetermined law, or during abnormal conditions causing overvoltages across the capacitor of the filter, by the insertion of said power dissipating circuit in place thereof, thereby permitting the use of a filter of smaller dimensions.
Claim 3
Dependent Claim
54 words
A chopper as defined in claim 1, wherein the switching device in series with the power dissipating circuit is a thyristor without any extinction circuit, and wherein the extinction of said thyristor is performed by means of a circuit breaker connected in series with said source and operated by said control and protection circuit.