| 摘要 |
PURPOSE:To improve operating efficiency, to prevent overexcitation and to reduce noise, by fluctuating the voltage applied in correspondence with the fluctuation of a load coupled to an AC motor. CONSTITUTION:A current sensor 16 detects the input current, i.e. the phase current, of an AC motor 5. Its output waveform is digitized with an A/D conversion circuit 18 through a current detection circuit 17, taken into a microcomputer 10 and compared with phase current data 10a. The microcomputer 10 produces a PWM wave in accordance with a frequency command 19 and an output voltage setting 10b. The voltage value applied in the same frequency is thereby varied and in accordance with the fluctuation of a load the applied voltage is fluctuated. |
