| 摘要 |
PROBLEM TO BE SOLVED: To break an arc of a large diameter produced by a large fault current in an intermediate voltage, while preventing the possibility of the bursting of an arc-extinguishing chamber. SOLUTION: This circuit breaker comprises a fixed contact means 20, a movable contact means 22, and an arc-extinguishing chamber 24. The arc- extinguishing chamber 24 has two side-fase flanges 68, a separator 78, the front opening formed near a contact region of the fixed contact means 20, a lower arc horn 34, an upper arc horn 96, and a set of side dielectric shields 100 limiting laterally the front opening 76 of the arc-extinguishing chamber. Each dielectric shield 100 is arranged laterally so as to be fitted between the separator 78 and the movable contact means 22 at an open position. The set of dielectric shields 100 are installed to clearly reduce a width of the front opening of the arc-extinguishing chamber 24 at a side nearer to the upper arc horn 96, in comparison with that at a side nearer to the lower arc horn 34.
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