permanent magnets 42 can be fixed between the bent portion 43 and the holder plate 45 by pressing the permanent magnets 42 in the axial direction by the bent spring portions 45a and also the permanent magnets 42 can be positioned in the circumferential direction by the spacers 45b and the bent portions 43a in this way the fixing of the permanent magnets 42 in the axial direction and in the circumferential direction can be performed in one motion by the holder plate 45 which is fitted in the yoke 40 therefore the total axial length does not increase more than the conventional case further the integrating operation can be performed only by fitting inserting and fixing the holder plate 45 into the yoke 41 and therefore the operational performance is improved further the commutating pole 44 does not have to be welded to the yoke 41 and the invention can handle a case wherein there is no commutating pole 44 in the above example 15 the punched out portions 43a formed on the bent portion 43 of the yoke 41 may not be provided and the construction may be as shown in fig3 in this case the positioning of the permanent magnets 42 in the circumferential direction can be maintained by increasing the spring forces of the bent spring portions 45a of the holder plate 45 which facilitates the working operation by dispensing with the punched out portions 43a in the.