| 摘要 |
PURPOSE:To reduce magnetic sound by always varying at timing the frequency of a carrier used to control the output of a PWM inverter, thereby suppressing the growth of mechanical resonance. CONSTITUTION:A rectifying bridge 1 converts an AC signal from a 3-phase AC power source 9 into a DC signal, which is applied to an inverter 2. A carrier generator 4 controls the frequency by the input voltage, and outputs a carrier of the frequency based on the pattern signal from a carrier controller 3 to a comparator 5. The comparator 5 compares the signals of an output voltage pattern generator 6 with the signal of the carrier generator 4, and outputs a PWM signal to a gate circuit 8. The gate circuit 8 amplifies the PWM signal and controls the inverter 2. The inverter 2 outputs an AC voltage proportional to the output signal of the generator 6, thereby controlling an AC motor 7. |
