摘要 |
PURPOSE:To improve the utility rate and the reliability of a power converter by continuously controlling the previous firing angle command value as an actual firing angle value when the counted value of a counter is abnormal, and treating a trouble only when it is continued for the prescribed time. CONSTITUTION:The firing control system of a power converter 7 by a digital calculator (microcomputer) has a waveform shaper 1, a counter 2, a timer 3, a microcomputer 4 and a pulse amplifier 5, and controls to fire the power converter 7 to supply the desired power to a load 8. Thus, it calculates an actual firing angle value alpha by the counted value of the counter 2 which operates by synchronizing with a synchronizing signal and outputs next firing pulse by the and next firing angle command value alpha*. When the counted value becomes abnormal at this time, assume that a firing pulse is output to the phase coincident to the value alpha* without using the firing angle alpha obtained from the counter 2, and the next firing pulse phase is decided by the previous value of the command value. When this is continued for the prescribed time, the prescribed treatment of a trouble is performed. |