JPS56159961A - Digital type phase control for thyristor - Google Patents

Abstract

PURPOSE:To enable to perform the phase control of about 100 steps covering 180 degrees by a method wherein after a zero-cross signal has been generated, the specified firing signal is outputted by discriminating the data for firing angle which was read-in at the time of a half cycle immediately before its operation and the digital arithmetic control circuit such as a delay microprocessor and the like are utilized. CONSTITUTION:When a zero-cross signal (b) is outputted at the time when the input voltage waveform sent from a zero-cross detector 8 is crossing the zero volt, a digital type control device 9 reads-in the firing angle data from a firing angle data setting device 7 and, at the same time, discriminates the firing angle data which was read-in at the time of a half cycle immediately before it is performed, and a firing signal (d) is outputted to a thyristor 5 at the prescribed time. Then, when the firing angle data which was read-in indicates a value other than 0 degree, the firing signal is reset at the prescribed time and when 0 degree is indicated, the outputted firing signal is maintained in that state without making a resetting.