As the silicon steel in the alternating magnetic field of the loss is very small, so the transformer is mainly made of silicon steel sheet for magnetic data. Silicon steel sheet can be divided into two categories: hot rolling and cold rolling. The cold rolled silicon steel strip is of low volume, light weight and high efficiency because of its high magnetic conductivity and low loss. The performance of hot rolled silicon steel strip is slightly inferior to that of cold-rolled silicon steel strip.
Ordinary EI transformer silicon steel plate is punched 0.35 - 0.5mm thick E and I films after heat treatment and then insert the winding line bag, this kind of core to use hot rolled silicon steel sheet (mostly high-quality silicon type high silicon content of D41, D42, D43, D301). The core ring and C type transformer is the use of cold rolled silicon steel strip winding and forming, wherein the C type transformer by heat treatment after dipping the cut is made.
The leakage inductance of the transformer is caused by the flux of the primary and secondary coils, which pass through the air and form a closed magnetic circuit themselves. It is possible to reduce the leakage inductance by increasing the coupling density between primary and secondary transformers. 1/100 good transformer leakage induction does not exceed the primary inductance of the output transformer, power amplifier with high fidelity Hi - Fi should not exceed 1/500.
One of the important parameters to judge the quality of the transformer silicon steel sheet for sound is the maximum magnetic line density of silicon steel sheet. Several high-quality silicon models commonly used are as follows: D41 - D42, the maximum magnetic flux density (unit - GS Gauss) 10000 - 12000GS; D43, the maximum magnetic flux density of 11000 - 12000GS; D301, the maximum magnetic flux density of 12000 - 14000GS.