| 摘要 |
PURPOSE:To detect reactive power containing no ripple by generating the product of a signal obtained by delaying the phase of a voltage by 90 deg. and a current and the product of a signal obtained by delaying the current by 90 deg. and the voltage, and subtracting those two signals by a subtracter. CONSTITUTION:A reactive power detector 10 consists of a voltage converter which detects the circuit voltage by a transformer 1 for an instrument and the circuit current by a current transformer 2 for the instrument and inputs them to convert a secondary voltage into a weak current circuit voltage, a current-voltage converter 4 which converts a secondary current into a weak current circuit voltage, 90 deg. phase delaying filters 5 and 8, multipliers 6 and 9, and the subtracter 7. Then, a voltage detected value is converted by the converter to a weak current level, which is inputted to a filter 8 and also inputted to the multiplier 6. A current detected value, on the other hand, is converted by the converter 4 to a weak current signal, which is inputted to the filter 5 and also inputted to the multiplier 9. Then, the outputs of the filters 5 and 8 are multiplied by the multipliers 6 and 9, whose outputs Q1 and Q2 are subtracted by the subtracter 7, so that its output Q=Q1-Q2 is detected as the reactive power. |
