| 摘要 |
PURPOSE:To make a potential distribution for a lightning impulse uniform and improve its insulation reliability by contact-winding a potential shield sheet around the surface of an insulating sheet which touches internally a cooling panel. CONSTITUTION:This device makes a potential shield sheet 21 come closely into contact to the surface of an insulating sheet 3 which is arranged so as to touch internally to the inside of a cooling panel 6 and the insulating sheet 3 comes into contact with an inside of the cooling panel 6 through this potential shield sheet 21 and a metal sheet 2 is wound in a coil so that its sheet 2 comes into contact with the outside of its panel likewise in the conventional cases. In the case of a foil-wound transformer made up in this way, even if a gap d develops at the inside of the panel 6, a capacitance between the cooling panel 6 and the metal sheet 2 at the inside of the cooling panel 6 comes to the capacitance between the potential shield sheet 21 and the metal sheet 2 and the above capacitance equals the capacitance between general metal sheets 2 which is determined according to thickness of the insulating sheet 3. Then a potential distribution for a lightning impulse voltage becomes uniform and improves the dielectric strength.
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