Flat coil for an electric machine

Abstract

A flat coil for use in a rotary electric machine has an annular row of generally radially extending and circumferentially spaced electrically conductive segments (1) on each annular end face of an electrically insulating base member (2). Each segment has a non-effective section disposed adjacent to the radially inner end of the segment and having a mean thickness greater than that of the remaining sections of the segment to improve the cooling ability of the coil. The segments are formed by punching a blank of thin copper sheet to form therein an annular row of radially extending and circumferentially spaced slits to thereby form an annular row of radially extending and circumferentially spaced segments. Before or after the blank is punched, the blank is subjected to forging, electrolytic plating, electrolyzing treatment or mechanical treatment so that the non-effective section of each segment has a thickness greater than that of the remaining sections. Thereafter, the annular row of segments is secured to an annular end face of the annular base member. A similar another annular row of segments is prepared and secured to the other end face of the annular base member. The segments of the two annular rows are then welded at their radially inner and outer ends to form three separate windings of coil around the base member. The annular rows of the segments are then severed along the outer and inner peripheral edges of the rows to separate the segments from the blanks to thereby complete the flat coil.