| 摘要 |
<P>PROBLEM TO BE SOLVED: To materialize cost reduction and low current consumption by stabilizing a trip time and lessening used parts. <P>SOLUTION: An arithmetic processing unit 14 calculates the thermal data having simulated the heat generation of a motor, based on a DC voltage signal outputted from an AC/DC converting circuit 1, and controls a switching element SW1 so that the calculated thermal data and the charge voltage of a capacitor C1 may accord with each other; and outputs a tripping signal in case that the calculated thermal data come to a preset tip level or over. This protective relay reads in the charge voltage of the capacitor C1, and switches on or switches off the switching element so that it may conform to the thermal data to perform closed loop control, so this can materialize high precision without cost up. <P>COPYRIGHT: (C)2004,JPO |
