| 摘要 |
A current limiting circuit breaker having for each pole, a pair of main contacts separable upon operation of a thermally and electromagnetically operable tripping device and a pair of auxiliary contacts for current limiting in series with the main contacts and in parallel with a transformable resistor having a positive temperature coefficient of resistance. The auxiliary contacts are separable when an electromagnet is energized by a fault current which simultaneously energizes a field magnet to produce a transverse magnetic field across the auxiliary contacts and the arc formed between them when separating. This simultaneous action of electromagnet and field magnet coacting for rapid contact separation and lengthening of the arc upon flow of a fault current serves to increase arc voltage almost instantaneously to that of the source, about which time the fault current is totally shunted into the resistor. One of the main contacts of each pole is carried by a movable contact blade. The contact blades have tapered mounting end portions which extend through an elongated molded plastic crossbar, the movable contact blade for each pole being mounted in spaced apart relation in the common crossbar. A metallic insert is embedded in the molded plastic crossbar, the metallic insert having spaced apart openings located to permit the tapered mounting end of the contact blades to extend therethrough.
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