PURPOSE: To make the winding work easy, and to improve the space factor, by covering the surface of a collecting conductor arranged parallel by at least three layers of insulating coverage layers, and securing a prescribed voltage resistance by either two layers of the coverage layers.

CONSTITUTION: An enamel covered conductor made by insulating-covering the outer periphery of a conductor 5a by an enamel coverage layer 5b is used as a raw wire 5. The diameter of the conductor 5a is preferable to make within a specific scope in order to increase the reduction effect of the high-frequency resistance. Plural enamel covered conductors 5 are arranged parallel in the condition to contact their sides each other so as to form a collecting conductor 6. In this case, an urethan vanish 5c is applied and baked to cover the whole surface of the conductors 5, so as to fix them. The surface of the collecting conductor 6 composed in such a way is covered by at least three layers of insulating coverage layers 7, 8, and 9. The coverage layers 7 to 9 can be divided each other, and they are formed to secure a specific voltage resisting property by either two layers of the three layers.