High RPM motor geared down?

Theoretically, if I had an electric motor that could spin at 30,000 RPMs, and I geared it down to say  3,000 RPMs, could I increase motor efficiency (and lower amperage draw) by having very high RPM, with super low torque, could it be efficient enough to produce a reasonable amount of torque and RPM?

2 Answers

  • 2 weeks ago

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  • 1 month ago

    Yes, in some cases; though usually with speed controlled system where the motor must run well below its maximum speed much of the time.

    That is why many motor-driven items and machine use reduction gearboxes in the first place.

    A gearbox reduces the required torque (or increases the motor torque, depending on your viewpoint) by the gear ratio.

    And, it decreases the load inertia seen by the motor, by the square of the gear ratio.

    The actual power used by the motor will be similar; if a load needs so many horsepower or KW, they that's still needed - but a higher motor speed, especially for something that moves slowly, is more efficient from the control point of view so can be rather more effective overall.

    Running the motor faster means lower current and higher voltage for the same power, and the current rating is largely what sets the costs of motors and drive systems.

    The optimum configuration is to match the maximum speed needed by whatever system or device, to be just slightly below the motor maximum speed.

    For a fixed-speed motor running directly from a fixed supply voltage, there would be no advantage & probably a disadvantage, as higher speeds may mean more expensive motors (to stand the stresses) and faster bearing wear; plus adding the cost of the gearbox.

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