| 摘要 |
PROBLEM TO BE SOLVED: To provide a determination method when dealing with an allowable foreign matter size easily and surely determining the allowable foreign matter size, after considering the effects by surge, when setting a DC-insulating material to an object of the allowable foreign matter size determination. SOLUTION: The minimum foreign matter size among an allowable foreign matter size HDC relative to the DC voltage, an allowable foreign matter size HImP relative to an impulse voltage, and an allowable foreign matter size HK determined by Burder coefficient, when a reversed-polarity impulse voltage is superimposed on the DC voltage is specified as the foreign matter size, allowing its inclusion in the DC-insulating material.
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