The core of S13 series transformers is made of the highest quality cold-rolled grain-oriented silicon steel sheets, and the stricter core manufacturing process places higher requirements on core materials and cutting equipment. In comparison, the no-load loss of S13 is 25% lower than the national standard value of S11, the no-load current of S13 is 80% lower than the national standard value of S11, and the noise can be reduced by 5-10dB.