Electric current produces heat. In early traction motor designs, the armature coils were soldered into special sections of the commutator bars called "risers". If heating from the electrical current raised motor current too high, the solder would melt, fly out and cause a flashover. The ends of the windings could also fly out, a process akin to "birdcaging", in which the armature windings come out of their slots. The primary limitation for the rating of a traction motor was dependent on its heat dissipation ability and was usually expressed in x number of amps continuous, y number of amps hourly, z number of amps short term, and so forth. What a traction motor blower does is facilitate heat dissipation, which raises the output of the motor. With the advent of TIG (tungsten intert gas) welded armature risers, the limitation imposed by solder's melting point was eliminated, leaving thermal breakdown of the armature insulation the only factor.

So when hotwater says the SW1's main generator didn't have the capacity to "over heat the motors", what it means is that the generator couldn't put out enough current to exceed the motors' continuous ratings, and this was in turn dependent on the HP of the diesel engine driving the generator.