①CD-type transformers are cheaper than R-type transformers, and have better electromagnetic properties than EI-type transformers; ②CD-type transformers have been standardized in my country as early as the end of the 1960s, so this type of transformer has good versatility and interchangeability. Also because of this, for users with a small amount of transformers, when using this type of transformer first, the capital investment is small and the effect is quick; ③CD-type transformers generally adopt the form of double-wire package (double is also called core-type transformer). Its stray magnetic field can be canceled, the magnetic interference is small, and the coil heat dissipation surface is large. It is suitable for processing medium and high-power transformers.