| 摘要 |
An PWM inverter of the present invention, for converting a direct current voltage to an alternating current voltage, generating voltage pulses, the width of said voltage pulses being modulated, corresponding to at least one of an output voltage demand and a fundamental wave frequency demand of said output voltage, comprises a period changing means for changing a voltage pulse output period, corresponding to the at least one of the output voltage demand and the fundamental frequency demand, and a modulation mode generating means for generating at least a mode of an asynchronous over-modulation mode generating a pulse of a wider width, generated in the vicinity of each peak of said output voltage fundamental wave, than widths of pulses generated in the vicinity of each zero-crossing of said fundamental wave as a PWM mode for controlling output voltages, wherein the period changing means gradually decreases the voltage pulse output period in order to increases the number of the narrow width pulses in the vicinity of each zero-crossing of the fundamental wave in the asynchronous over-modulation mode. <IMAGE> |
