Conduction state monitor for high voltage rectifier - is used to initiate turn or if insufficient elements reach blocking state

摘要

In rectifiers for high voltage with many thyristor elements in series the effect of scatter in turn-off times may occasionally result in an inadequate number being in the off state when voltage is reapplied. A circuit is needed to rapidly detect this condition and retrigger all series devices to prevent damage. Monitoring elements from the thyristors provide inputs (e1-en) to a first OR-gate (1) whose output (b) passes both directly to a second OR-gate (4) and to an inverter (2) in series with a monostable multivibrator (3) with a time delay just long enough to incorporate the full scatter of late turn off signals. The multivibrator is triggered by the first pulse and remains on until the pulses arrive in quick succession.