Multi-phase converter including a harmonic filter

Claim 1

A MULTI-PHASE CONVERTER INSTALLATION FOR THE EXCHANGE OF ELECTRICAL POWER BETWEEN A MULTI-PHASE A.C. SYSTEM OPERATING AT A PREDETERMINED FUNDAMENTAL FREQUENCY AND A D.C. SYSTEM, THE CONVERTER INSTALLATION COMPRISING A MULTI-PHASE TRANSFORMER HAVING A PRIMARY WINDING AND A SECONDARY WINDING, A PLURALITY OF CONTROLLED RECTIFYING DEVICES CONNECTED TOGETHER AS A BRIDGE CIRCUIT, MEANS CONNECTING THE SAID BRIDGE CIRCUIT BETWEEN THE SAID SECONDARY WINDING AND THE SAID D.C. SYSTEM, MEANS CONNECTING THE SAID PRIMARY WINDING TO THE SAID A.C. SYSTEM, AND A HARMONIC FILTER FOR SUBSTANTIALLY REMOVING EACH ONE OF THE HARMONIES OF THE SAID PREDETERMINED FUNDAMENTAL FREQUENCY IN THE SERIES 5TH, 7TH, 11TH, 13TH, 17TH, 19TH, 23RD, 25TH ... HARMONICS, THE SAID HARMONIC FILTER COMPRISING A PLURALITY OF FILTER BRANCHES EACH CONNECTED ACROSS A RESPECTIVE SAID PHASE OF THE A.C. SYSTEM, AND EACH SAID FILTER BRANCH COMPRISING A PLURALITY OF PARALLEL-CONNECTED TUNED CIRCUITS, WHICH PLURALITY IS LESS THAN THE NUMBER OF SAID HARMONICS IN THE SAID SERIES, EACH TUNED CIRCUIT BEING TUNED TO A RESPECTIVE ONE OF THE SAID HARMONICS, EACH FILTER BRANCH ALSO INCLUDING A CAPACITIVE REACTANCE CONNECTED IN PARALLEL WITH ALL THE TUNED CIRCUITS OF THE BRANCH, SAID CAPACITIVE REACTANCE BEING ARRANGED TO BE IN PARALLEL RESONANCE WITH ALL THE SAID TUNED CIRCUITS IN THE BRANCH AT A FREQUENCY BETWEEN THE HIGHEST ONE OF THE SAID HARMONICS TO WHICH ANY SAID TUNED CIRCUIT IS TUNED AND THE NEXT HIGHER ONE OF THE SAID HARMONICS IN THE SERIES.