Lamination joint reluctance in stator cores - A forgotten problem?

Stator cores of large electrical machines most commonly use half-overlap lamination joints. These can cause magnetic saturation in the region of the joints, such that by flux levels of 1.2 T the toroidal reluctance for a typical core can increase by 200% over that expected. Magnetic anisotropy can conversely reduce expected toroidal reluctance, though by only 18-30%. While long predicted, their impact on magnetic circuit design and especially high flux stator core testing remains apparently unrecognized in industry. The saturation phenomenon is studied and its net effect on the toroidal B/H response of a stator core predicted with FE models and validated by test.