Abstract: Magnetic-pole pieces each equipped with a pair of insulators made of resin are provided with a conductive wire wound continuously via a jumper wire making connection between the magnetic-pole pieces, and are arranged in an annular shape. Each insulator has, at one end in a circumferential direction of an axial-direction end, a snap-fit female portion having an opened-ring portion having an opening, and has, at another end, a snap-fit male portion having a pillar portion extending in the axial direction from a base portion. The adjacent magnetic-pole pieces are connected swingably relative to each other via snap-fit connection by fitting of the pillar portion to the opened-ring portion. A jumper-wire-caught portion at which a jumper wire is caught is provided at least in one location of the connection part where mutual connection is made.