| 摘要 |
In a direct current cutoff switch 1, a PTC 5, which is a non-linear resistor, is parallel connected to a contact circuit composed of a fixed contact 4 - 2 and a movable contact 8 - 2 via electrodes 5 - 1. When the switch is closed, no current flows in the PTC 5 with a prescribed resistance value at 25° C., since voltage between both the electrodes 5 - 1 is almost "0". When the switch is opened in order to cut off current, the contacts form a closed circuit since the PTC 5 is parallel inserted between the fixed contact 4 - 2 and the movable contact 8 - 2. For this reason, it is difficult for surge voltage to occur and an arc hardly occurs between both the contacts. The PTC 5 instantaneously heats due to passing current, reduces the resistance value and passes peak current. Then, the resistance value rises and becomes stable in a high value such that weak current which is negligible at 42V, which is rated voltage. Thus, current is substantially cut off.
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