Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

DC Motor speed vs load

  1. May 8, 2017 #1
    Hi, I am modelling a DC motor using Simulink.
    Under no-load conditions, I get a max speed of 180 rads/s, but under load, the speed goes up to 290 rad/s, although takes longer to reach max speed, acceleration decreases.
    I have a mechanical background so don't know much about motors, but would expect that, under load, the speed would reduce?
    Any ideas?
    Many thanks.
     
  2. jcsd
  3. May 8, 2017 #2

    Baluncore

    User Avatar
    Science Advisor

    Assuming it is a simple DC motor with brushes.
    Torque is proportional to current. Back EMF is proportional to RPM.
    Applied voltage – back EMF appears across the rotor resistance and so decides current.
    Unloaded speed will be proportional to applied voltage.
    Increasing load will slow the motor until current rises to give torque required.

    You have a problem with your model.
     
  4. May 9, 2017 #3
    Ok, thanks Baluncore. I need to review what's happening.

    Cheers
    Nick
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: DC Motor speed vs load
Loading...