| 摘要 |
PURPOSE:To improve the efficiency and to reduce a noise by setting the minimum pulse width at output frequency to approximately constant time to satisfy the limit switching time intrinsic for a power semiconductor element, thereby reducing the low order harmonic waves in the output. CONSTITUTION:A frequency designation setter 16 generates a voltage proportional to a voltage supplied from a DC power source 25, and the voltage is converted by a voltage/frequency converter 17 to a rectangular pulse of the frequency proportional to the voltage. The rectangular pulse is converted by a triangular wave converter 18 into a triangular wave, and further converted by a sinusoidal wave converter 19 to a sinusoidal wave. An amplitude controller 20 controls the amplitude of a sinusoidal wave to a voltage proportional to a command frequency. The output of the setter 16 is input through a function generator 21, a voltage/frequency converter 22 and a triangular wave converter 23 to a comparator 24. The comparator 24 compares the outputs of the controller 20 and the converter 23, and generates a pulse train.
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