The article is diplomatic, but not ambiguous. For instance: > Cooling issues: can enough cooling air be forced inside the rotors? > Cooling issues, again. Th

The article is diplomatic, but not ambiguous. For instance: > Cooling issues: can enough cooling air be forced inside the rotors? > Cooling issues, again. The primary cooling path for more traditional motors is usually conduction through the stator yoke, to the frame, to either air or coolant fluid. For the HET, this path seems almost completely missing. > [four lines later] Assuming the cooling performance remains unchanged, the reduced winding losses could then be cashed in by increasing the current density, and thus torque, torque-per-mass, and bringing losses back to the original level. This may read as if there are good ideas here, but make no mistake- the implication is that these problems are nigh-unworkable. The possibilities of minor increases are locked behind immense problems. There is a parallel with combustion engines here. The ideal combustion cylinder is spherical: it ensures more even burning and minimizes the area heat from escape from a given volume. You could make an engine with spherical combustors instead of cylindrical and reap that improvement. That's basically what toroidal motors try to do- use more surface area per unit of rotor volume (although due to the nature of air gaps[not discussed in the article], it's not obvious that this is actually beneficial). In both cases, you're cutting off your nose to spite your face.