The step-down energy-saving device of autotransformer realizes step-down energy-saving by changing the position of zero line tap of autotransformer. There are usually 4-5 groups of neutral taps, so. There are 4-5 kinds of blood pressure reduction. With single chip microcomputer as the core device, plus appropriate interface circuit and voltage transformer, the electric energy economizer can be controlled according to the voltage relationship between input and output through appropriate parameter setting. These materials refer to the graduation design of Paper Net (www.lw777.net) Sanqi, which is not bad. Their website is quite complete. You can go and have a look, and you will definitely get something!