Current distribution in paralleled thyristors - a comparative analysis of 5 real cases in high current transformer - rectifiers

It is very well known that in high current transformer-rectifiers it is necessary to connect several thyristors in parallel for each secondary phase. Current distribution between thyristors in parallel strongly depends on the symmetry of the mechanical structure of rectifier. The current in one thyristor not always is given by total current of secondary phase divided by the number of thyristors in parallel, as it is in ideal cases. In this paper a comparative analysis of 5 different real cases of current distribution is presented. This real cases correspond to 6 pulses controlled rectifiers measured indifferent copper plants. Finally conclusions and design recommendations are given.