| 摘要 |
PURPOSE:To increase the average power factor after compensation by changing the gain of compensation of a reactive power compensating device in response to the shift bias value equal to the quantity of load electricity. CONSTITUTION:A reactive power compensating device consisting of a capacitor, a thyristor, etc. is provided to an AC power supply connected to an arc furnace having large fluctuation of load. A reactive power detecting circuit of said compensating device is provided with a thyristor firing angle control circuit 14, a multiplier 15 serving as a variable gain circuit, a primary delay circuit 16 serving as a shift bias arithmetic circuit, a subtraction circuit 17, a gain setting circuit 18 and an addition circuit 19. When the reactive power QA is generated, the shift bias QM is calculated by the circuit 16 and multiplied by the power QA via the circuits 17-19. As a result, the output of the reactive power compensating device shows the large value in an area having small power QA and compensates completely the value smaller than the compensation capacity.
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