PURPOSE: To improve the efficiency of a motor, by forming a hollow at a projection provided on the outside circumference of an iron core and by fixing into the outside circumference of the projection a non-magnetic material having a lug to fit into the hollow.

CONSTITUTION: Projections 2 are provided on the four(4) spots of the outside circumference of an iron core 1 on a concentric circle and hollows 3 are formed in the plane central portion of the outside circumference of the projections 2. On to the outside of a projection 2 a non-magnetic nonferrous metal 4 such as aluminium, etc. is fixed. The lugs 5 of the non-magnetic material 4 are pressed into the hollow 3 and fixes. Housing 9 and 11 supports the iron core 1 through the non-magnetic material 4. Flanges 10 and 12 are bent and formed to match together outwards the open edge of housings 9 and 11. Thus the magnetic resistance between the iron core and the housing becomes larger, improving the efficiency of a motor.