The open-type dry transformer is a kind of air-cooling dry power transformer with H-level insulation non-coating coil which is manufactured with vacuum pressure impregnation (VPI) process by adopting the technology in America Du Pont Company. The product is made by drying after vacuum pressure impregnation for many time, which owns excellent moisture protection and moisture resistance performance. So the product safety greatly improves. The product owns the following advantages such as security, reliability, energy conservation and environment protection, fire and explosion protection, overload capacity, small volume, simple maintenance, etc.; it's applicable to the indoor environment with high fire rating requirements, large load fluctuation and frequent overload operation, so the product is put into the urban architecture, high-rise buildings, underground construction and other environment in quantity.