A generator includes a stator with a stator winding, a rotor with a field winding supported for rotation relative to the stator, and a housing enclosing the stator and the rotor. The housing has an independent system port that is connected to a shared system port by a selector. The selector fluidly couples the stator and one of the independent system port and the shared system port. The selector also fluidly separates the stator from the other of the independent system port and the shared system port. Generator arrangements and methods of making generators are also described.