Control system of three-phase rectifier power factor correction circuit

摘要

PROBLEM TO BE SOLVED: To lower the capacities of controlling elements and thereby obtain a low-cost power factor improvement circuit for a three-phase rectifier by unifying two short-circuit modes into one. SOLUTION: In a power factor improvement circuit for a three-phase rectifier constituted of six controlling elements Q1-Q6 and six diodes D1-D6, there are two modes in which three controlling elements are shorted at the same time. In one mode, the controlling elements Q1-Q3 at the positive side of the rectified DC voltage are shorted, and in the other mode, the controlling elements Q4-Q6 at the negative side are shorted. By unifying the two modes for shorting three controlling elements into a single mode, for example, into a mode wherein the controlling elements Q1-Q3 are shorted, a quantity of current in the controlling elements at either the positive or negative potential side is lowered, and thereby small-capacity and low-cost controlling elements can be used.