How Can A High-Torque Motor Have Low a low RPM

  1. Torque is the rotational force.
    If there is more force, how can the motor be slow?

    I'm building a DC motor and read that given a constant amount of coil, creating a very dense coil will increase torque but lower RPMs.
    Conversely, making it looser (bigger radius) increases RPM but lowers torque.
     
  2. jcsd
  3. Simon Bridge

    Simon Bridge 14,444
    Science Advisor
    Homework Helper
    Gold Member

    The torque gives you acceleration - but it is possible to accelerate to any speed... however slow.

    For your motor - it will accelerate to a constant speed due to losses that are proportional to speed. This will be proportional to the amount of mass that has to be spun - and so is the torque.
     
  4. rcgldr

    rcgldr 7,398
    Homework Helper

    The increase in torque at lower rpm is offset by increase in back emf at higher rpm, which decreases the torque at higher rpm.
     
  5. russ_watters

    Staff: Mentor

    Motors are connected to loads. The load determines the ratio between RPM and torque. If a "high torque" motor is not connected to a load and is just allowed to freewheel, it does not produce any torque.
     
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