| 摘要 |
PURPOSE:To improve the stability of low voltage and low power operation, by performing arithmetic on voltage signal having drooping characteristic in proportion to the output AC voltage of an inverter, and by comparing voltage signal which is sine-wave-modulated further, with the momentary value of said AC voltage. CONSTITUTION:The detecting circuit of the angle of advance for an inverter is composed of an AC/DC converter 1 for generating the output of DC voltage following up the fluctuation of input AC voltage exactly and proportionally, inversion arithmetic units 2, 5, an adding arithmetic unit 3, a sine function generator 4, a wind comparator 6, and gamma-angle setting units 7, 8. The detection value of the angle gamma of advance is changed according to drooping characteristic shown in a formula which is not shown in figure against the change of the output voltage Vi of the inverter, and in the low voltage range of said voltage Vi, a constant angle according to a constant is made larger than a fluctuating angle based on the voltage Vi, and the desired angle gamma is secured. As a result, gamma-angle detecting characteristic for increasing the margin angle of inverter commutation along with the lowering of the output voltage Vi can be obtained.
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