CROWBAR DEVICE AND MULTISTAGE CROWBAR APPARATUS

摘要

A crowbar device is provided. The crowbar device has a first terminal (1) and a second terminal (2), the terminals (1, 2) being connectible to a medium to high impedance AC voltage source (AV), the crowbar device comprising a trigger circuit (B) connected between the first terminal (1) and the second terminal (2) and configured to output a trigger signal responsive to exceeding a threshold voltage across at least one trigger element of the trigger circuit (B); a positive-side signaling circuit (C) and a negative-side signaling circuit (D) configured to output a positive or a negative clamping signal, respectively, according to a positive-voltage or a negative-voltage signal, respectively, input from the trigger circuit (B); and a positive-side overvoltage clamping circuit (E) and a negative-side overvoltage clamping circuit (F) each comprising a controllable semiconductor element (ES, FS) connected between the first terminal (1) and the second terminal (2), the overvoltage clamping circuits (E, F) being configured to control their respective semiconductor element (ES, FS) to be in a conducting state, when the clamping signal from the corresponding signaling circuit (C, D) is present, and configured to control their semiconductor element (ES, FS) to be in a non-conducting state, when the corresponding clamping signal has not been present for a predetermined time period.