Rectifiers with Reactor-Input Filters

Table VII gives commonly used rectifier circuits, together with current and voltage relations in the associated transformers. This table is based on the use of a reactor-input filter to reduce ripple. The inductance of the choke is assumed to be great enough to keep the output direct current constant. With any finite inductance there is always some superposed ripple current which is neglected in the table, and which is considered further in Rectifier Performance.

Table VII - Table of Rectifier Circuits

This table is based mostly on "Polyphase Rectification Special Connections," by R. W. Armstrong, Proc. I.R.E., Vol. 19, Jan. 1931.

The single-phase half-wave rectifier ordinarily has discontinuous output current, and its output voltage is therefore highly dependent upon the inductance of the input filter choke. For this reason, the currents and voltages are given for this rectifier without a filter.

The difference between primary and secondary v-a ratings in several of these rectifiers does not mean that instantaneous v-a values are different; it means that because of differences in current wave form the rms values of current may be different for primary and secondary.

Unbalanced direct current in the half-wave rectifiers requires larger transformers than in the full-wave rectifiers. This is partly overcome in three-phase transformers by the use of zigzag connections. The three-phase full-wave rectifier can be delta-connected on both primary and secondary if desired; the secondary current is multiplied by 0.577 and the secondary voltage by 1.732. Anode windings have more turns of smaller wire in the delta connection. Single-phase bridge and three-phase full-wave rectifiers require notably low a-c voltage for a given d-c output, low inverse peak voltage on the tubes, and small transformers.