| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a detector for detecting a drop of an alternating current voltage capable of detecting quickly the drop in the voltage, irrespective of a phase of the drop in an alternating current system voltage. <P>SOLUTION: In this detector for detecting the drop in the alternating current voltage, a voltage detection signal and a signal phase-advanced by 90° with respect thereto are computed in addition to the first voltage drop signal generated by a conventional detector for detecting the drop in the alternating current voltage, a higher harmonic component is reduced by a low pass filter, in an alternating current voltage amplitude computed based on the two signals to be compared with a prescribed value, the voltage drop is judged thereby to generate the second voltage drop signal, and the voltage drop is detected when the voltage drop is found in any of the first voltage drop signal and the second voltage drop signal. <P>COPYRIGHT: (C)2005,JPO&NCIPI |
