Method for protecting thyristors of a converter and system therefor

摘要

In order to prevent the damage of thyristors in a converter such as an inverter or chopper due to deviations of their characteristics, margin angles of commutation in respective arms of the converter are detected and compared with a predetermined value. If a margin angle is smaller than the predetermined value, all thyristors of the arm are fired to fail in commutation and are thus protected from excess current or voltage.