Quote:
Originally Posted by Kevin Sevcik
No-load = free speed. That is, the speed the motor turns at when nothing at all is connected to it. Note, that this doesn't mean no amps are being pulled. There's still a small amount of friction to be overcome etc. Plus, the rotor coils are constantly changing orientations and making and breaking contacts. This means the magnetic fields are constantly collapsing and reforming, which means the back emf generated by the motor will vary over time. Since the voltage supply nominally stays the same and the coils have some resistance, current is flowing whenever the back emf doesn't exactly equal the input voltage. So all DC motors have a no-load current as well as a no-load speed.
Which brings me to another silly technical point. Since the CIM is drawing current it has some non-zero input power, even at no-load. However, since there isn't a load output from the shaft, it has zero output power. So the motor's efficiency at no-load is actually 0%, not 100%.
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I was referring to no load in the sense of robot sitting there with wheels in the air-ie:no load on the gearbox, not no load on the motor. I was a little unclear there.
As to the second point, I meant 100% efficiency as in zero frictional losses in the drivetrain, not 100% motor efficiency.