| 摘要 |
PURPOSE:To reduce a noise generated from an AC motor in a wide speed range irrespective of a load state by detecting the phase voltages of the motor, and limiting the amplitude of a voltage command value on the basis of the phase voltage signal. CONSTITUTION:A current limiter 17 outputs a voltage signal V<+> of the amplitude proportional to a deviation i between a current command signal i<+> and a current detection signal (i) to a limiter 81. The limiter 81 limits the basic wave of the signal V<+> so that a voltage command signal Vc<+> falls within the prescribed amplitude value. The signal Vc<+> is applied as a modulation wave to an adder 19. The adder 19 inputs the triangular signal T generated from an oscillator 18 and the modulation wave Vc<+>, outputs the prescribed output signal, and a pulse generator 20 generates a PWM pulse on the basis of the output signal from the adder 19. The switching element of the interver 1 is controlled to be ON or OFF by the PWM pulse. When the voltage signal is thus limited, the wasteful switching number due to a ripple is eliminated by limiting the voltage signal to reduce the noise particularly at the low speed operating time. |
