Direct digital control of thyristor amplifiers

The direct digital control of thyristor amplifiers, in which each thyristor is directly under the control of the control computer, is described. This technique combines the normal advantages of computer control, such as a stored reference program, high accuracy steady-state control and the ability to calculate complex control functions, with those of full logical control of the amplifier. In addition, it dispenses with the need for a digital-analogue converter. A full description is given of the implementation of a computer-controlled 3-phase bridge amplifier in a closed-loop voltage control, including the individual addressing and firing of the thyristors from the accumulator of the computer, and other details of the control algorithm. Results are given from experiments with 2-, 3- and 6-phase star systems in addition to the 3-phase bridge system.