Double winding transformer is used in almost all electronic products. Its principle is simple. However, according to different applications (different purposes), there are different requirements of the winding process of the double winding transformer. The functions of double winding transformer are as follows: voltage conversion; impedance transformation; isolation; voltage stabilization (magnetic saturation transformer); protect the human, etc. The commonly used core shapes of double winding transformers are generally E-type and C-type cores.
The most basic type of transformer is two groups of coils with conductors, which are combined in the form of inductance. When an alternating current (with a known frequency) flows into one group of coils, an alternating voltage with the same frequency will be induced in the other group of coils. The induced voltage depends on the degree of the coupling of two coils and the magnetic cross chain.
Generally, the coil connected to the AC power supply is "primary coil". The voltage of this coil is called "primary voltage". The induced voltage in the secondary coil may be greater than or less than the primary voltage, which is determined by the "turn ratio" between the primary coil and the secondary coil. Therefore, the double winding transformer can be divided into two types: step-up transformer and step-down transformer.
Most of the double winding transformers have fixed iron core, on which there are primary and secondary coils. Based on the high conductivity of iron, most of the flux is limited in the iron core. Therefore, a high degree of magnetic coupling can be achieved between the two coils. In some double winding transformers, the coil and core are closely combined, and the ratio of primary voltage to secondary voltage is almost the same as the ratio of turns of the two coils. Therefore, the turn ratio of the double winding transformer can be used as the reference index for the step-up or step-down of the double winding transformer. Because of this, the double winding transformer has become one of the important accessories of modern power system. With the function of increasing and decreasing the transmission voltage, the long-distance transmission is more economical. As for the step-down double winding transformer, it makes the power application more diversified.