The core of the ui transformer is an important component of the transformer. The basic requirements for the material are low core loss at a certain frequency and flux density, and high magnetic flux density at a certain magnetic field strength. The core of the early ui transformer was made of iron rods, and later it was changed to iron cores. Because soft iron or mild steel has the advantages of high magnetic permeability, low coercive force, low price and good manufacturability, the core of ui transformer is mostly made of hot rolled low carbon soft steel sheet or electromagnetic pure iron sheet.
With the new smelting and rolling annealing process, it has begun to vigorously develop cold-rolled silicon-free low-carbon electrical steel sheets and electromagnetic pure iron electrical sheets. Silicon-free electrical steel sheets have the advantages of low price, good punching performance and high magnetic induction. The addition of silicon to mild steel can increase the electrical resistivity of steel, reduce the eddy current and hysteresis loss of steel, and improve the aging of steel sheets.
The early silicon steel sheet was a hot-rolled silicon steel sheet with a low silicon content and a general Si content of 1-2% (Grade B), which was mostly used in electric motors. With the advent of cold rolled silicon steel sheets, the output of hot rolled silicon steel sheets has gradually decreased. Since the cold-rolled silicon steel sheet has the advantages of low loss, reliable quality, uniform thickness, and smooth surface, it has been widely used and replaced hot-rolled silicon steel sheets in many occasions.