The load circuit protection device

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PROBLEM TO BE SOLVED : To provide a protective device for a load circuit, which detects the temperature rise of an electric wire and reliably interrupts the load circuit when a chattering short-circuit or a rare short-circuit occurs. SOLUTION : When a current flowing through the electric wire 7 is normal, the rising temperature of the electric wire is calculated by using an algorithm of (A-1) if the saturation temperature of the electric wire 7 by a detecting current is higher than the estimated temperature of the electric wire 7. The falling temperature of the electric wire is calculated by using the algorithm of (B-1) when the saturation temperature of the electric wire 7 by the detecting current is lower than the estimated temperature of the electric wire 7. When the current flowing through the electric wire 7 is an overcurrent, the rising temperature of the electric wire is calculated by using the algorithm of (A-2) if the saturation temperature of the electric wire 7 by the detecting current is higher than the estimated temperature of the electric wire 7. The falling temperature of the electric wire is calculated by using the algorithm of (B-2) if the saturation temperature of the electric wire 7 by the detecting current is lower than the estimated temperature of the electric wire 7. When the temperature of the electric wire reaches a threshold temperature, the load circuit is interrupted. COPYRIGHT : (C)2010, JPO&INPIT