Three-phase transformers are widely used in circuits with AC voltage below 660V from 50Hz to 60Hz, and are widely used in imported important equipment, precision machine tools, mechanical and electronic equipment, medical instruments, rectifier devices, lighting and so on. Various input and output voltages, wiring groups, the number and position of regulating taps (generally 5%), the distribution of winding capacity, the equipment of secondary single-phase winding, the application of rectifier circuit, whether it is required to have a shell, etc. This product can be carefully designed and manufactured according to the requirements of users.