A hermetically-sealed turbomachine, such as a motor-driven blower and a turbine driven generator, capable of reliable high-temperature operation, especially for large sized turbomachine includes a hot blower, compressor or turbine end of the turbomachine that is separated from the cooler electric motor, generator or alternator end of the turbomachine by a compliant mechanical coupling and a thermal choke assembly. The turbomachine housing is also hermetically sealed, providing control over the process gas within the machine housing, and permitting an internal cooling method within the turbomachine, whereby a small amount of process gas itself is used within the turbomachine for providing cooling of the rotating shafts, the axial fan, radial fan, or turbine impeller, the bearings and the electric motor, generator or alternator disposed within the turbomachine housing. The cooling method can be aided by a heat exchanger operatively communicating with the turbomachine.