PURPOSE: To obtain cores with small saturation current and small iron loss and a high magnetic permeability in a normal operation by laminating cores of different saturation magnetic fluxes in size to each other.

CONSTITUTION: The first material a such as ferrite permalloy core 21 with relatively high magnetic permeability and the second material b such as permalloy silicon steel plate core 22 whose magnetic permeability is smaller than the material a, are laminated. Normally the material a with a higher magnetic permeability works and when the material a becomes saturated by the flux HS, the permeability becomes small, moving to the B-H curve of the material b and, even in the state of deflected magnetism, the magnetizing current changes from the saturated current of them material a alone to the magnetizing current of the material b thereby controlling magnetizing current.