OIL IMPREGNATED CAPACITOR

PROBLEM TO BE SOLVED: To stabilize electric characteristic for a long term by using a polypropylene film having molecular weight distribution where the ratio of weight-average molecular weight to number-average molecular weight is set to be at most a specified value, as a plastic film. SOLUTION: Polypropylene is synthesized by using mixed catalyst such as metallocene catalyst and methyl aluminoxane, refined, extruded and drawn to a specified thickness, thereby forming a polypropylene film. In the polypropylene film, Mw/Mn which is the ratio of weight-average molecular weight Mw to number-average molecular weight Mn is set to be at most 3. This polypropylene film or an object where the polypropylene film and an insulating paper are combined is made dielectrics. The dielectrics and conducting foils are alternately stacked, wound and impregnated with synthetic oil. An oil impregnated all film capacitor or oil impregnated paper film capacitor is formed. As a result, elution of polypropylene into oil is reduced, and fluidity of oil can be maintained for a long term.