Insulated wire and winding

An insulated wire, comprising:

• a conductor;
• a first insulation coating layer that is provided directly on the conductor and comprises a polyamide-imide resin including 4,4′-diphenyl-methane diisocyanate and 2,4′-diphenyl-methane diisocyanate as isocyanate components and dispersed inorganic fine particles, the first insulation coating layer being formed from an insulating coating material comprising a mixture of a polyamide-imide resin coating material and an organosol, the polyamide-imide resin coating material including the polyamide-imide resin including the 4,4′-diphenyl-methane diisocyanate and the 2,4′-diphenyl-methane diisocyanate as the isocyanate components dissolved in a solvent including cyclic ketones having a boiling point within a range of 130° C. to 180° C., and the organosol including the inorganic fine particles dispersed in a dispersant including not less than 70% by mass of cyclic ketones having the boiling point within the range of 130° C. to 180° C.;
• and
• a second insulation coating layer that is provided directly on an outer circumference of the first insulation coating layer and comprises a polyamide-imide resin or a polyimide resin,
• wherein a minimum winding multiplied diameter that does not cause a crack in the first insulation coating layer when the insulated wire is elongated by 30% by a method in compliance with JIS C 3216 “5.1.1” and is wound around a winding bar is greater than 2d but smaller than 4d, where d is a conductor diameter of the insulated wire,
• wherein the second insulating coating layer serves as a stress relaxation layer which relaxes stress generated in the first insulation coating layer,
• wherein a retention rate of v-t characteristics, which is a time to breakdown under measurement conditions of applied voltage of 1.0 kVrms, sine wave of 10 kHz and normal temperature, after pressing at a press-down rate of 40% is not less than 30% of an original state, which is a state before pressing,
• wherein a mixing mole ratio of the 2,4′-diphenyl-methane diisocyanate in the isocyanate components is in a range from 15 mole % to 25 mol %, and
• wherein the dispersant of the organosol is composed of 80% of cyclohexanone and 20% of γ-butyrolactone, and, the solvent of the polyamide-imide resin coating material is composed of 80% of cyclohexanone, 15% of γ-butyrolactone, and 5% of N-methyl-2-pyrrolidone (NMP).