| 摘要 |
PURPOSE:To make it possible to increase a current upto the limit value when a motor current is increased, by detecting the overcurrent, and controlling a pulse- width modulating means by a triangular-wave generating means and a timer. CONSTITUTION:A command signal and a speed signal for an induction motor 1 is input of a V/f converter 24, and the output pulses are supplied to a sine-wave generator 27 via a frequency divider 26, thereby an artificial sine wave is output. On the other hand, the output of a triangular-wave generator 28 is compared with the sine wave in a comparator 29, given to a pulse-width modulator 30 to control transistors Q, thereby the rpm of the motor 1 is controlled. When a load current exceeds a limit value, the output of a comparator 33 is supplied to a timer 31 and the triangular- wave generator 28, thereby the transistors Q are controlled. Therefore, the current to be flown to the motor can be fully increased upto the limit value, and the large torque can be generated. |
