Insulated wire and rotating electrical machine

1. An insulated wire, comprising:

at least one foamed insulating layer composed of a thermosetting resin having bubbles, directly or indirectly on an outer periphery of a conductor,

wherein the thermosetting resin is selected from a polyamideimide resin, a polyimide resin, a polyamide resin, a polyetherimide resin, a polyesterimide resin, and a polyethersulfone resin,

wherein the foamed insulating layer has a difference in a bubble density in a thickness direction thereof to be 3% or more, and

wherein an average bubble diameter of the foamed insulating layer is 10 μm or less.

2. The insulated wire according to claim 1 , wherein a difference of the bubble density in the thickness direction of the foamed insulating layer is 3% or more and 90% or less.

3. The insulated wire according to claim 1 , wherein an average bubble diameter in the foamed insulating layer is 1 nm or more and 10 μm or less.

4. The insulated wire according to claim 1 , wherein a thickness of the foamed insulating layer is from 10 to 200 μm.

5. A rotating electrical machine comprising the insulated wire according to claim 1 .