| 摘要 |
PURPOSE:To simplify the mechanism of a controller for a 3-phase AC load by varying the period of a control signal and a pulse time width by the prescribed relationship to the input signal by a microcomputer, thereby continuously controlling phase direction and phase frequency of 3-phase current. CONSTITUTION:A 3-phase AC power source drives and controls a 3-phase induction motor 12 through a 3-phase transformer 11 and switching transistors 13-15. When controlling ON or OFF the transistors 13-15, the desired digital information n is set through an A/D converter 2 from an external control input circuit 1, and is converted through the first table 3 and the second table 4 formed of ROM into information T representing the periods and information B representing the pulse time width. Output signals t1-t3 are obtained from this, a clock signal 6 counted by a counter 5, and a reset signal R of the period T fed from a commercial power source through a zero cross detector 8 and the prescribed detecting means 9, 3-phase pulse signals P1-P3 are formed through a oneshot multivibrator 7, thereby controlling the transistors 13-15. |
