| 摘要 |
<p>PROBLEM TO BE SOLVED: To obtain an inspection method in which it is not required to sample a test piece and which does not damage a product by a method wherein a hot air is blown on a sheet of oil-impregnated insulating paper as an object, to be tested, by using a hot-wind spraying device so as to be heated instantaneously to a temperature at a specific temperature or higher and whether a cloudy phenomenon is generated on the sheet of oil-impregnated insulating paper as the object to be tested is investigated visually. SOLUTION: A sheet of oil-impregnated insulating paper as an object to be tested is heated instantaneously to a temperature of 100 deg.C or higher. As a heating means, a small and general- purpose hot-wind spraying device such as a hot jet or the like is used. By using the hot-air spraying device, a hot air is sprayed on the sheet of oil-impregnated insulating paper as the object, to be tested, for about several to several tens of seconds. When the temperature of the sheet of oil-impregnated insulating paper as the object to be tested becomes 100 deg.C or higher, a water vapor is generated. When moisture at about 1% or higher which influences an insulating performance is adsorbed, air bubbles due to the water vapor are generated so as to display a cloudy phenomenon. The cloudy phenomenon is discriminated visually and easily. Thereby, whether the moisture absorption of the sheet of oil-impregnated insulating paper exists or not can be judged, it is not required to sample a test piece as different from conventional deep-fired tests, and a product is not damaged.</p> |
