With increasing of high pressure, the two stage compression cycle with two gas cooler has a downward trend. With increasing of the evaporating temperature, the two stage compression cycle with two gas cooler has an increasing trend. With increasing of outlet temperature of condenser; the two stage compression cycle with two gas cooler has a downward trend. With increasing of intermediate pressure, the performances of the two stage compression cycle with two gas cooler are decreased.

Taking 1000MW air-cooled hydro-generator as an example, the solving region and mathematical model are given. Based on the theories of electromagnetic field, the stator iron loss of large generator under non-load is studied. Considering the structural characteristics of generator, the iron loss was calculated by using magnetic circuit method and the finite element method, respectively. First, the iron loss in generator stator is calculated basing on the theory of electromagnetic field. Then the steady state and transient fields were used to calculate and analyze the 2D electromagnetic field by finite element method. And the exact value and distribution of iron loss are obtained. Last, we obtain some useful conclusions through comparing the iron loss calculated by the two methods above. That will provide a theoretical basis for further study of the physical fields of new generation giant hydro-generators.

With increasing of compressor high pressure, the two stage cycle with an expander has a downward trend. With increasing of the evaporating temperature, the two stage cycle with an expander has an increasing trend. With increasing of outlet temperature of condenser; the two stage cycle with an expander has a downward trend. With increasing of intermediate pressure, the performance of the two stage cycle with an expander is decreased.