Inverter surge-resistant insulated wire, having an enamel baked layer, an adhesive layer, and an extrusion-coated resin layer, around the outer periphery of a conductor, wherein the sum of the thickness of the enamel baked layer, the extrusion-coated resin layer, and the adhesive layer is 60 μm or more, wherein the thickness of the enamel baked layer is 50 μm or less, and wherein the extrusion-coated resin layer is formed from a polyphenylene sulfide resin composition, which contains a polyphenylene sulfide polymer having a melt viscosity at 300° C. of 100 Pa·s or more, 2 to 8 mass % of a thermoplastic elastomer, and an antioxidant, and which has a tensile modulus of elasticity at 25° C. of 2,500 MPa or more, and a tensile modulus of elasticity at 250° C. of 10 MPa or more.

We developed polyesterimide (PEI) nanocomposite enameled wires using surface-modified silica nanoparticles with binary chemical compositions on the surface. The modification was done using silanes assisted by ultrasound, which facilitated high density modification. Two different trimethoxysilanes were chosen for the modification on the basis of resemblance of chemical compositions on the silica surface to PEI varnish. The surface-modified silica was well dispersed in PEI varnish, which was confirmed by optical observation and viscosity measurement. The glass transition temperature of the silica-PEI nanocomposite increased with the silica content. The silica-dispersed PEI varnish was then used for enameled wire fabrication. The silica-PEI nanocomposite enameled wire exhibited a much longer lifetime compared to that of neat PEI enameled wire in partial discharge conditions.

Enameled wire is composed of conductive copper or aluminum core surrounded by an insulation layer made of polymer. The lifespan of the electric motor is strongly dependent on thermal and electrical properties of the insulation layer. In a high speed switching inverter-fed motor, especially, when instantaneous overlapping voltage called surge voltage is higher than partial discharge inception voltage (PDIV), the insulation layer is degraded by partial discharge (PD), which leads to insulation breakdown. For this reason, surge-resistant enameled wire has attracted attention for prolonging the lifespan of various inverter-fed motor installed electric devices such as electric vehicles.

For protection from the degradation, nanosized inorganic fllers were incorporated in the insulation layer  where corona evolved by PD can be trapped on or reflected from the surface of the inorganic fllr so that the degradation would be retarded.

Previous：Natural Magnet Wire Formvar Heavy Build Round Aluminum Magnet Wire
Next：High thermal aging surge insulated enameled wire