Insulated wire, and electric/electronic equipments, motor and transformer using the same

1. An insulated wire having a rectangular shaped cross-section, comprising:

a conductor having a rectangular shaped cross-section; and

an insulating layer coated to the conductor,

wherein the insulating layer has a foamed layer composed of a thermosetting resin containing bubbles, the cross-section of the insulating layer has a shape composed of a flat portion and a corner portion, and the insulating layer satisfies the relationship represented by the following formula:

∈ 1 <3 and ( T 2 /∈ 2 )>( T 1 /∈ 1 )

wherein T 1 [μm] represents a thickness of the flat portion; ∈ 1 represents a relative dielectric constant of the flat portion; T 2 [μm] represents a thickness of the corner portion; and ∈ 2 represents a relative dielectric constant of the corner portion.

2. The insulated wire according to claim 1 , wherein the insulating layer further satisfies the relationship represented by formula: (T 1 /∈ 1 )>15.

3. The insulated wire according to claim 1 , comprising non-foamed layer containing no bubble, on the inner periphery and/or the outer periphery of the foamed layer.

4. The insulated wire according to claim 1 , wherein the foamed layer comprises at least one thermosetting resin selected from the group consisting of a polyamideimide resin and a polyimide resin.

5. The insulated wire according to claim 1 ,

wherein the insulating layer comprises an extruded layer, and

wherein the extruded layer comprises a crystalline thermoplastic resin having a relative dielectric constant of 4 or less and a melting point of 260° C. or more.

6. An electric/electronic equipment, a motor, or a transformer, comprising the insulated wire according to claim 1 .