The compound cross-section H-class non-encapsulation cored dry transformers developed by Shanghai EK Group and Shenyang transformer research institute changes the traditional magnetic circuit structure and the overall layout of the transformers, and thus makes the technology of the transformer reach the international advanced level, and it has the advantages of energy-saving and environment-protection. The three phase no-load current of the transformer is balance, and the no-load loss and no-load current is even lower, about 40% and 80% lower than the national standard. It is of the small size, light weight, and low noise, and is more and more popular among the users. The product is widely used in the skyscraper, shopping center, airport, subway, railway stations, docks, oil, chemical, nuclear power stations, nuclear submarines, densely populated areas, light rail, power plants and other places where is need to be fire-retardant and explosion-proof.