Transformers have various other uses besides converting AC voltage, such as changing the frequency of power sources, supplying power to rectification equipment, supplying power to welding equipment, supplying power to electric furnaces, or serving as voltage transformers, current transformers, etc. These transformers with special purposes are collectively referred to as special transformers. Due to the different working conditions and load conditions of these transformers compared to general transformers, they cannot be calculated using the calculation methods of general transformers. There are mainly energy-saving transformers, ZSG series rectifier transformers, EPS, UPS dedicated transformers, QZB series step-down starting autotransformers, and BK series control transformers.