| 摘要 |
PURPOSE:To operate a motor at a variable speed by a PWM control type inverter having high efficiency by fixing the ratio of the amplitude of a carrier signal to that of a sine wave control signal to a predetermined value under a PWM control of an inverter main circuit. CONSTITUTION:A transistor 20a of an inverter main circuit 20 is controlled to be driven based on a PWM signal. In this case, control ratio (A2/A1) of the amplitude A1 of a carrier signal Sc to that A2 of a sine wave control signal Ss is fixed to '1'. When a motor 21 of 100V/60Hz specification is operated by 120Hz, a DC voltage converter 12 steps up the output voltage under V/F constant condition. In this case, the control ratio (A2/A1) of the amplitude A1 of the carrier signal to the amplitude A2 of the signal So of an inverter controller 22 is '1'. When the rotating speed of the motor 21 is reduced, the controller 22 remains '1' of the ratio, and the output voltage of the circuit 12 is stepped down by a microcomputer 23. |
