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Electric motor and generator

  1. Dec 4, 2013 #1
    Hello all,
    So I am confused about a a scenario and I hope you guys can hook me up with some explanation.
    So I am trying to find the initial force needed for an electric motor to turn. I am not looking for torque or energy just the Newtons just to start from scratch and keep going with the math. with a force X during a certain time with a length Y of the shaft, etc.. I think this is the best way to understand how does the electric motor work. so if I have a the motor connected to a wall plug or running on gas or battery how much force will it take that after we convert it to torqu it will be enough to turn the electric motor shaft.
    now lets assume the motor shaft hooks to a small generator through a belt. How much force will the generator need to turn.
    I believe the force of the motor should be the sum of both forces or something within those lines. Can you guys tell me how to get the initial force on each, just the force to get it to start turning. I am attaching a little drawing to show the setup.
    please use any initial assumptions you want as long as it serves the purpose of finding the initial force.
    Thanks alot for your time and help

    Attached Files:

  2. jcsd
  3. Dec 4, 2013 #2
    Do you know how to find the torque of the motor? From there you can relate the force given you have the dimensions of the rotor.
  4. Dec 5, 2013 #3


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    I'm still trying to figure out how to run an electric motor on gas. Hmmm...
  5. Dec 7, 2013 #4
    thanks all, that was fast.. :)
    so Assuming that I need 10HP to start moving an electric car. HP=CxFxRPM/33000. usually it is 2TT (TxRPM)/33000 but torque is FxR and 2TT xR is C (circumference).
    So F=CxRPM/330,00 x 10 =CxRPM/330,000. But How would I find the RPM at start, can I assume it is 1 RPM (just to get the car moving)
    And the major question is: if the motor uses a 100N force that gives a 200Nm Torque (just for example). Will the torque on the generator attached to the shaft (in the picture above) be the motor force x the shaft or axle distance to where the generator connects to the motor?
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