| 摘要 |
PURPOSE:To take a measurement with high accuracy even at the time of less loading, specially, a starting current by comparing a pulse frequency converted in proportion to electric power with a reference frequency, and performing control over a metering state and switching control over a changeover switch for inputting a consumed current and a pulse distributing circuit. CONSTITUTION:A signal proportional to the load voltage of a feeder is extracted by a transformer 1 for instruments and supplied to a pulse-width modulation type time- division multiplying circuit 3, and a consumed current extracted by a current transformer 2 is supplied to the circuit 3 through the changeover switch 6. A signal proportional to the electric power is supplied to a frequency discriminating circuit 20 through an LPF4 and a voltage-frequency converting circuit 8. The circuit 20 consists of a reference frequency generation part 21, frequency comparison part 22, AND gate 23, and discrimination signal generation part 24. The reference frequency of the generation part 21 is considered to be equivalent to the output frequency of the circuit 8 at the time of the starting current of a watt-hour meter and the pulse distributing circuit 7 is controlled by the output of the gate 23. Further, the output of the generation part 24 controls the circuit 7 into a nonmetering state and performs switching control over the switch 6 to take a high-accuracy measurement of a tidal current. |
