One is that the primary coil is connected to the power supply, and the other two coils have more turns for boosting and less turns for stepping down
Transformer is a device that uses the principle of electromagnetic induction to change AC voltage, and its main components are primary coil, secondary coil and iron core (magnetic core). In electrical equipment and wireless circuits, it is often used for voltage rise and fall, impedance matching, safety isolation and so on. The main functions are: voltage transformation, current transformation, impedance transformation, isolation, voltage stabilization (magnetic saturation transformer) and so on. It can be divided into distribution transformers, power transformers, fully sealed transformers, combined transformers, dry-type transformers, oil-immersed transformers, single-phase transformers, electric furnace transformers, rectifier transformers, etc.