DC Motor Efficiency at a given operating point

I would expect some major tradeoffs could be:

• cost, size, stability margin to load variations, RPM range, Torque max (continuous,peak)
• cooling{water,air}, sound level, temp rise, MTBF,
• start current, driver cost
• and efficiency.

These appear to be all 600Vdc 3 phase, (air or water cooled) high torque 2 to 20Hp range motors.

You can compute power efficiency at max rating which is given as V,I and Watts of dissipation, continuous, max rated. at 160'C max coil temp.

Given magnets tend to weaken with ambient temp rise, I would think you want to keep these cool for reliability reasons and derate 50%. The smallest motors might be maxing efficiency at rated speed, but the bigger heat generators will probably work at best efficiency (hunch) with power de-rated 50% by a few % effic. The water-cooled give more power capacity but also loses 2.5% efficiency or so with water pumping.

I put a few numbers into a spreadsheet for your consideration.

Since these are PMSM you have to interpolate the max current, the voltage at your desired RPM and consider the efficiency of your Variable speed drive (VSD) driver and power source available.