| 摘要 |
PURPOSE:To improve the precision of phase discrimination by providing the phase discriminating circuit which decides on the phase relation between the plural quantities of AC input electricity, and shifting the phase of the 1st quantity of AC input electricity; from the phase of the 2nd quantity of AC input electricity by a specific angle and discriminating pulses of the two kinds of AC electricity. CONSTITUTION:The 1st quantity 1 of AC electricity proportional to the zero-phase voltage of a circuit to be measured and the 2nd quantity 2 of AC electricity proportional to the zero-phase current are inputted. A phase shifting circuit 11 shifts the phase of the quantity 1 of AC electricity from the phase of the quantity 2 of AC electricity by the specific angle of electricity. Further, the quantities 1 and 2 of AC electricity are inputted to and made into rectangular waves by rectangular wave circuits 13a and 13b, and the waves are shaped by inverters 14a and 14b and inputted to the 1st and the 2nd pulse generating circuits 15a and 15b. Their outputs are inputted to the 3rd pulse generating circuit 16, which outputs a phase discrimination signal VN. An arithmetic circuit 19 processes the phase discrimination signal VN. and a level signal VD and performs phase discrimination to output a signal. Thus, the phase discrimination is carried out without any malfunction against a noise.
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