Steam turbine condensing-back pressure two-purpose machine

The utility model relates to a steam turbine with functions of condensing and back pressure, comprising a high, a medium and a low pressure cylinder, a condenser, a generator and a valving, wherein the high, medium and low pressure cylinders and the generator are mounted on concentric shafts; the condenser is connected with the low pressure cylinder; the valving is provided on the pipeline between the high and medium pressure cylinders and the low pressure cylinder; a 3S clutch, which two sides are connected with the high and medium pressure cylinders and the low pressure cylinder separately, is fixed between the high and medium pressure cylinders and the low pressure cylinder. The utility model can operate with back pressure manner in winter and condensing manner in summer with advantages of low coal and electric consumption, high thermal efficiency, cost saving and obvious economic and environmental benefits with broad application.