For those, on the list, who cannot digest attachments, here is what I wrote. It was in response to an article in IEEE/Power Engineering Review on an electric motor having some windings made of high temperature superconductors ["HTS"]:
"This is about units of measurement. See "Sparks", Pg. 44 of IEEE POWER ENGINEERING REVIEW 2001 October. In "World's First HTS 5,000-HP Motor", we see horsepower featured to quantify output power. The input to that motor would, almost certainly, have been measured in watts. That being the case, how would the efficiency (output/input) have been expressed? - hp/kW? And supposing the electrical losses would have been measured in watts (kW, MW etc.), would the mechanical losses be in hp? This, by any standards, would seem to be an irrational situation. "The IEEE has made great strides in adopting the World system of units, SI. How can we, engineers, extricate ourselves from the use of such disjointed units as described above? Surely, we are ready for motors whose output is in standard power units - watts. An important step woudl seem to involve NEMA. It would be useful if "MG-1" would include a section for the output of motors in SI units. Hopefully, they would 'start from scratch' and select one Series of Preferred Numbers. The selection of standard outputs of motors smaller than 1 kW could, in particular, be considerably improved over the fractional and milli- horsepower ratings now listed. "By the way, doen't it seem especially incongruous that a motor as modern as the HTS would be rated in such archaic units?" Hope there aren't too many typos in this. By the way, NEMA is National Electric Manufactures Association. MG-1 is a standard (Motors and Generators) which includes tables of standard outputs for motors and generators. The outputs pertaining to generators are all in SI units. The standard ratings for motors contain tables in integral hp ranges, in fractional-hp ranges and in (get this) milli-hp ranges. They use two *different* Preferred Number series in the motor tables. The fractional hp tables do not 'track' the preferred number line very well in places because of the limits imposed in using fractions. Disclaimer: I am referring to the situation back in 1995. Duncan
