| 摘要 |
PURPOSE:To raise reliability as well as obtain time limit characteristics by simplifying treatment for effective value operation. CONSTITUTION:The device consists of the absolute value operation block 11 by which to obtain an absolute value from the instantaneous value of sampling current, the shift resistors 121 to 12m by which to hold the absolute value of m numbers of the past instantaneous values, the max. value detection circuit 13 by which to detect the max. value of the past and present data, the comparator 14 by which to compare the detected value with predetermined value, the time value conversion circuit 15 by which to receive signal above the predetermined value, and the timer circuit 16 by which to receive signal below the predetermined value. In this system, the absolute value of n/2cycle.min. instantaneous value is compared by basic frequency to extract max. value, if the max. value exceeds predetermined value, it is converted into time value which is in turn set in timer for starting, and then the working of the timer gives protective output. |
