A new interruption method for low-voltage, high-capacity, air-break contactors suppressing the blowoff of a hot gas

A method was derived to suppress the blowoff of a hot gas from an arc chamber and to shorten arcing time in the interruption of overcurrents. The blowoff of the hot gas is suppressed by cooling with a porous metal plate attached in front of gas-exhausting holes of an arc chamber. From heat analysis, it is estimated that the temperature of the hot gas passing through the porous metal plate is lowered by about 95%. Arcing time is shortened by a unique commutation electrode and arc runner. In the interruption of a current of 6 kA at a 480 V circuit, the maximum arcing time is shortened by about 40%. From observation by a high-speed framing camera, it is concluded that the shortening of arcing time is due to an effective arc-drive by the commutation electrode and arc runner. This method has been applied to contactors of 600 A and 800 A frames having the maximum-rated operational voltage of 660 V.<
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