PURPOSE: To reduce eddy-current loss at the high magnetic flux density portion by a construction wherein an inner winding core is formed of a silicon steel belt thinner than that used for an outer winding core so as to make small the residual stress due to deformation of the inner winding core.
CONSTITUTION: Inner winding cores 1 and 2 are formed of a silicon steel belt with thinner thickness (0.20W0.25mm). An outer winding core 3 is formed of a conventional silicon steel belt (0.27W0.35mm). At the time of assembling the core, both cores 1 and 2 are deformed against their bending peculiarity when inserted. But this deformation is made such that the cores 1 and 2 can be returned with a small force to the shape of their bending peculiarity prior to the deformation. Thus, the residual stress at the corner parts of both cores 1 and 2 becomes small. Further, both cores 1 and 2 have generally high magnetic flux density, so that eddy-current loss is made small in both cores 1 and 2.
UEDA TAICHI
SAKAMOTO MASARU
