| 摘要 |
PROBLEM TO BE SOLVED: To prevent loss reduction due to switching by setting a frequency out of an audible range in order to suppress a sound of a carrier frequency from affecting the surroundings in motor drive by PWM control.SOLUTION: A frequency command applied from the outside is inputted into a carrier frequency receiver 10 which converts the frequency command into a command signal received by a carrier frequency variable inverter 20 as required to output it as a carrier frequency command. The carrier frequency variable inverter 20 performs PWM control to supply electric power to a motor 30 on the basis of a Duty command applied from the outside and the carrier frequency command. A switching frequency of inverter output is changed when the carrier frequency command changes from AHz to BHz. In that case, a ratio of ON to OFF is not changed when the Duty command does not change. A ratio of ON to OFF of the switching is changed when the Duty command changes. |
