Parallel operation of bridge rectifiers without an interbridge reactor

Abstract

Parallel connection of rectifier circuits is needed for very high direct-current supplies such as those for electrochemical plant. Appropriate phase displacement of their AC supply voltages is used to increase the pulse number, and an interrectifier reactor, often known as an interphase transformer (IPT), is connected on the DC side to prevent circulating AC components between the rectifiers and to allow them to operate independently. At very high power levels, this component is occasionally dispensed with on economic grounds. The interactions between two six-pulse bridge rectifiers operating without an IPT are described and analysed comprehensively. The rectifier, transformer winding and AC-system current waveforms are computed, together with their harmonic components, and some typical operating characteristics are given. Computed results are supported by practical measurements on a laboratory rectifier system. It is noted that removal of the IPT will considerably influence the rectifier transformer design.