| 摘要 |
PURPOSE:To detect accurate electric power at high speed and also detect the electric power of a power system whose tidal variation is large by providing a sum and difference arithmetic circuit and sampling and holding primary converted values of the voltage and current of the electric power system. CONSTITUTION:The sum and difference arithmetic circuit 31 calculates three specific instantaneous values on the basis of the voltage and current of the electric power system. A multiplexer 51 inputs the instantaneous value outputs which are sampled and held by a sample holding circuit 4 to an A/D converter 52 while switching those values. In figure, ROM 53 is a memory for a look-up table. Consequently, the circuit 31 derives primary converted values from detected values of the voltage and current of the power system and those converted output values are sampled and held by a circuit 4. Its sample holding output is passed through a multiplexer 51 and then processed digitally by a digital processing circuit 52, and a microprocessor 6 computes and outputs electric power proportional to the digitally processed signal according to a preset program data.
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