| 摘要 |
PROBLEM TO BE SOLVED: To prevent abnormal wear by opening a contact mechanism in a short time without malfunction by the use of the force of a blast, by providing a relay device for opening the contact mechanism and energizing an actuator thereof to actuate a release means when the pressure of the blast is higher than a fixed value. SOLUTION: An actuator 24 is energized at a fixed value by a compression spring 25a or an energizing member so as to close a blast hole 23. When the pressure of a blast exceeds the fixed value, the actuator 24 is turned to cause a trip operation, thereby opening a contact mechanism 4, and a fixed value of pressure is set up. In the case of a lower-current rated circuit breaker, a relay device 30 is used having a projection part 37a whose height is set lower in a case 37. This causes a spring holder 26 abutting on the projection part 37a to be shifted leftwards in the Figure, thus disposing the compression spring 25a in a state of lower load, Therefore, the actuator 24 closes the blast hole 23 by a smaller energizing force and is turned by a smaller blast pressure.
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