Rectifier Transformer is a type of transformer that is specially designed for rectification systems, which are used to convert alternating current (AC) to direct current (DC). Rectifier Transformers are widely used in various industrial applications, such as aluminum electrolysis, electric arc furnaces, traction substations, DC transmission systems, etc. Rectifier Transformers have some special features, characteristics and working principles that make them different from ordinary transformers. This article will introduce these aspects of Rectifier Transformers and explain why they are special.