PURPOSE: To reduce the number of assembly works by arranging a hole into which a support provided on a coil winding bobbin side surface is inserted, at a position butting a lead wire draw-out hole at a main member side plate, and arranging so as to make positioning when an exciting coil has been assembled.

CONSTITUTION: First, the power source lead wire 20 and the earth lead wire 20' of an exciting coil 11 which are inside furnished with a seal member 21 formed of, for example, such an elastic material as rubber or the like, and which are pressure-welded to male terminals 23, 23' that are put into female terminals 22, 22' and make a sure introduction, are inserted into the draw-out hole 13d of a yoke main member 13. After a coil-bobbin portion set 30 has been set so as to have terminals 22, 22' and the cores of terminals 23, 23' agreed upon, an assembly is done in a direction in which each terminal is put into the member 13. A plurality of pointed projections 15d are integrally provided on the side plate 13c side of the member 13, and a hole 13f into which the projection 15d is inserted on the side plate 13c, is arranged at a set position where terminals 23, 23' are put into terminals 22, 22', and the length of the projection 15d is made to be a length positioning the set 30 before respective terminals 22, 22', 23, 23' come into contact. As a result, connection and insertion can be done with precision.