The Collaborative International Dictionary of English v.0.48:

Turbogenerator \Tur`bo*gen"er*a`tor\, n. [See Turbine, and
   Generator.]
   An electric generator or dynamo which is combined on one
   frame with a turbomotor, by which it is driven.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

turbogenerator
    n 1: generator consisting of a steam turbine coupled to an
         electric generator for the production of electric power