The operation mode of the steam turbine stage in low-steam and motor modes is considered. The features of the operation of the steam turbine stage in the motor mode are given. It is shown that the condition accepted in earlier studies of hydrodynamic processes in the turbine stage during its operation in the motor mode, that the cooling steam flows through the stage without expansion, i.e. without generating active power, is valid if the entire flow part of the turbine is under pressure in the condenser and there is no pressure drop in the stages. The conditions under which the stage operates in the ventilation mode or in the mode of generating active power are determined. The technique developed with this condition in mind allows, with known parameters before the stage and the pressure ratio before and behind the stage, to determine the operating mode of the stage.