Protection apparatus for load circuit

A protection apparatus for a load circuit, which protects the load circuit when a temperature of an electric wire rises in the load circuit which supplies a power output from a power supply to a load to drive the load, the protection apparatus comprising:

• a count unit which is adapted to count an elapsed time;
• a current detection unit which is adapted to detect a current flowing through the electric wire of the load circuit;
• a switch unit which is adapted to switch between connection and interruption of the load circuit;
• a temperature calculation unit which is adapted to set a pseudo heat capacity smaller than a heat capacity of the electric wire used in the load circuit, and to calculate the temperature of the electric wire with reference to an arithmetic expression of heat generation amount of the electric wire, an arithmetic expression of heat radiation amount of the electric wire, the time counted by the count unit, and the pseudo heat capacity;
• and
• an interruption control unit which is adapted to interrupt the switch unit when the temperature of the electric wire calculated by the temperature calculation unit reaches an allowable temperature of the electric wire.