There is no low, medium or high for variable speed...It's "variable speed". :thumbsup: X13 motors have speed taps, for different static requirements (your supposed to check static to determine speed requirement). I would think the only concern is staying below max rated amperage.
..and if you're trying to compare speed "control" of multi-speed PSC motors to ECM motors...there's no comparison.
True speed control for AC motors is via motor "poles"...6 pole-1200, 8 pole-900 etc. Most multi-speed PSC motors are 6 pole (1200 rpm) and have the run winding "tapped" at differ locations, effectively reducing the horsepower, which when under load, reduces the speed.
ECM motors are DC motors with permanent magnet rotors...variations in speed are accomplished by changing the field voltage, which is what the controllers do. Even then, the controllers "see" power relative to some CFM value. Drops in power are translated as reductions in airflow, so the motor increases in speed to maintain the power/air volume.
Air movement is mass flow.
Mass flow is work.
Work requires energy.
More work more energy.
PSC motor higher static less work less energy lower amp draw.
ECM constant torque higher static will maintain torque (amps).
ECM constant CFM ( almost allways incorrectly called variable speed and if we really want to be picky, it's pounds of air not boxes as in CFM) higher static faster rpm more work to try to maintain CFM higher amp draw.
ECM constant CFM low static lower work less amps.
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