Polyphase Rectification Special Connections

Characteristics of various rectifier circuits and factors governing their selection are given. It is pointed out that in general, the double 3-phase circuit is most desirable from the standpoint of transformer and tube capacity requirements for mercury pool type tubes, and the 6-phase single Y for hot cathode mercury vapor tubes or high vacuum tubes, but that other factors may make other circuits more desirable for particular cases. Data are given for 3-, 4-, 6-, and 12-phase rectifiers using T-connected transformers, so that fewer transformers are required. Since it is cheaper to build two large transformers than three smaller ones of approximately the same total capacity, the T-connection may permit a saving in transformer cost. The voltage doubling circuit is discussed, its relation to other single phase circuits shown, and its characteristics given as a function of the product, CR, of condenser capacity and load resistance.