| 摘要 |
PROBLEM TO BE SOLVED: To establish a method for deciding the arc space of an air circuit breaker which allows simple measuring works and can set the arc space with a high precision. SOLUTION: A sonic wave generating device 8 is furnished at one end of the space surrounding an arc extinguishing chamber 4, and sound collecting devices 9 and 10 are provided a certain distance L apart in the sonic wave transmitting direction of the wave generating device 8, and pulsed sonic waves S are transmitted from the device 8 at time intervalsΔt, and the wave transmission timesΔt1 toΔt3 of the heated air 5 in the upper space of the arc extinguishing chamber 4 at the time of break are measured from the time difference between the sonic waves S0 and S1 which are received by the sound collecting device 9 and 10, followed by determination of the temp. T and voltage withstand value from the densityρof the heated air 5 determined from the measured transmission times, and thereby it is possible to set the arc space having a spatial distance from the air circuit breaker concerned 1 having the specified temp. and voltage withstand value.
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