| 摘要 |
PURPOSE:To obtain a detector by providing a first operational means which calculates the effective power of each phase, a second operational means which determines the instantaneous value of its effective power, and an angular frequency conversion means. CONSTITUTION:A voltage transformer 2 detects voltage components Vu, Vv, Vw of a three-phase power line 1, and a current transformer 3 current components Iu, Iv, Iw. A multiplier 4u latches Iu and Vu to multiply them, a multiplier 4v to multiply Iv and Vv, and a multiplier 4w to multiply Iw and Vw. Their products are added and subtracted by an adder/subtractor 5, and sum/remainder P latched into a comparator 8 through a bandpass filter 6. The filter 6 makes 2w, the twice of the angular frequency w of a power source, pass. The comparator 8 compares the output value of the filter 6 with the set value of a setter 7, latches the deviation into a monomultivibrator 9, and obtains a negative phase current detection signal. |
