| 摘要 |
PROBLEM TO BE SOLVED: To provide a protective device for a load circuit capable of detecting temperature rise of wire to reliably interrupt the load circuit when a rare short-circuit occurs.SOLUTION: When current flowing through a load 4 is increasing, rising temperature of wire 7 is calculated on the basis of heat characteristics (thermal resistance and heat capacity) of the wire 7 or a contact conductor. Furthermore, when the current flowing through the load 4 is zero or decreasing, dropping temperature of the wire 7 is calculated on the basis of the heat characteristics of the wire 7. Then, the determined rising temperature and dropping temperature are totally added, thereby current temperature of the wire 7 is estimated. When the estimated temperature exceeds predetermined allowable temperature, a load circuit is interrupted. Therefore, highly accurate circuit protection on the basis of temperature rise of the wire 7 can be achieved. |
