Logic behaviour of h.v. d.c. convertors during normal and abnormal conditions

The behaviour of the currents in valves in a 3-phase full-wave bridge convertor follows a sequential pattern which can be represented as a sequence of ON/OFF operations analogous to binary logic in digital computers. A generalised table is derived which specifies the conducting sequences for any possible mode of operation of a convertor, including fault conditions and subsequent recovery periods where appropriate. The combinations are related to time zones bounded by reference grid pulses and voltage zeros in the a.c.-supply waveform.