Insulated wire and preparation method thereof, coil, and electronic/electrical equipment

An insulated wire, comprising a conductor, with an intermediate layer and an insulating layer sequentially coated on the conductor, wherein

• the intermediate layer comprises polyamide-imide and polyimide, and a mass ratio of polyamide-imide to polyimide in the intermediate layer is (8-30):
• 1;
• the insulating layer comprises thermoplastic polyimide and a corona-resistant material, and a mass percentage of the corona-resistant material in the insulating layer is 6%-10%;
• the corona-resistant material is selected from at least one of titanium dioxide, silicon dioxide, and aluminum oxide;
• a thickness ratio of the intermediate layer to the insulating layer is 1:(13-18);
• and
• a preparation process of the insulated wire comprises:
• forming the intermediate layer by multiple times of coating and curing to obtain a core material, mixing the thermoplastic polyimide and the corona-resistant material, and then melting and extruding the mixture onto an outer side of the core material to form the insulating layer;
• and
• a preparation process of the insulating layer comprises:
• mixing the thermoplastic polyimide and the corona-resistant material to obtain an insulating layer mixture, and then melting and extruding the insulating layer mixture under a negative pressure condition and at a temperature of 370° C.-410° C., with controlling a vacuum suction used to apply the negative pressure to be greater than or equal to 0.3 MPa;
• and
• before the melting and extruding, the core material is preheated to 200° C.-320° C.