Analogue-computer study of a convertor jump phenomenon

Abstract

In naturally commutated controlled convertor equipments, damping circuits are frequently connected from anode to cathode to control the rate of rise of voltage at the end of commutation. In certain convertor configurations employing interphase transformers, these damping circuits may result in a convertor regulation having a large and undesirable discontinuity at low currents. The discontinuity is a function of interphase-transformer reactance, damping capacitance and firing-pulse duration. The paper shows how a very complex circuit may be reduced, with the aid of appropriate simplifications, to a relatively simple mathematical model or equivalent circuit, which not only simplifies computation but allows the mechanism of the phenomenon to be visualised. An outline is given of the analogue-computer techniques used, and results obtained, in the study of 6-pulse and 12-pulse configurations. It is shown that suitably long firing pulses eliminate the undesired jump phenomenon.