Microprocessor based controller for a three phase bridge rectifier

摘要

A method of controlling a six pulse bridge phase controlled rectifier using a microprocessor is provided by the invention herein. The method involves synchronizing an oscillator to the frequency of an ac power source and driving first and second counters with the oscillator. The first counter is used in conjunction with a phase locked loop to monitor and adjust the oscillator frequency. The count of the second counter generates an alpha value used in a firing angle match routine. The match routine compares the desired output voltage to the cosine of alpha minus an inductance factor. The match routine takes less than 20 microseconds to run allowing a new alpha value to be checked every 0.5 degrees for a 60 hertz power source. When a match is found, the thyristors are fired and a reload value projecting a subsequent firing in 60 DEG is calculated for the second counter.