The S11 series transformer core uses high-permeability, low-loss cold-rolled oriented silicon steel strip and a unique lamination structure to minimize the distortion of magnetic flux density, thereby significantly reducing no-load loss and no-load current. Because the core joint air gap of this type of transformer is small and the joints of each layer are staggered, the no-load loss is smaller, the no-load current is lower, and the noise is reduced by 5-10dB.