Low kVA/kW transformers for AC to DC multipulse converters

摘要

A polygon connected autotransformer in conjunction with zero sequence blocking inductor(s) enables multipulse AC to DC converters to use lower kVA parts rating by using appropriate phase-shifted voltage sets in conjunction with inductors that extend the conduction period and reduce rms current. Also, lower harmonic voltages in the transformer facilitate use of lower performance magnetic steel. Designs for 12, 18, and 24-pulse use the same conceptual approach. Very efficient high power ratings are feasible. Means are given to limit the maximum no-load DC output voltage. A technique is disclosed that reduces the size of polygon transformers supplying loads with substantial third harmonic.