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

Force necessary to spin an alternator at the rated RPM?

  1. Oct 24, 2009 #1
    Can anyone tell me how to determine the force necessary to spin an alternator at the rated RPM?
     
  2. jcsd
  3. Oct 24, 2009 #2

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    Re: alternator

    No, because that depends upon properties of the specific alternator. In particular, the friction in the alternator itself and the time in which it is brought up to that RPM.
     
  4. Oct 24, 2009 #3

    russ_watters

    User Avatar

    Staff: Mentor

    Re: alternator

    ....and the electrical load on the alternator.
     
  5. Oct 24, 2009 #4
    Re: alternator

    ok hypotheically then, let's say it's a 6000 watt generator head taken from a portable home backup generator. if i have 6400lbs-ft of constant force and the generator head operates at either 3600 rpm or 1800 rpm...without knowing the specific details such as mass(approx. 60-80lbs of rotational parts) or friction, is it possible to determine the force necessary? also does anyone know of a website that offers detailed information on alternators and/or suppliers that I could purchase one from?
     
  6. Oct 24, 2009 #5

    Ranger Mike

    User Avatar
    Science Advisor

    Re: alternator

    about 5 horsepower for 100 amp alternator
     

    Attached Files:

  7. Oct 24, 2009 #6
    Re: alternator

    Torque (Newton-meters) in angular rotation is the equivalent to force (Newtons) in linear motion. For an alternator, the power output (watts) is the product of the angular force times the angular speed. Specifically

    T x 2 pi RPM/60 = W watts, where the torque T is in Newton-meters.

    So for a 6000 watt alternator output (at 100% efficiency) at 3600 RPM, the torque is

    T = 60 W/ 2 pi RPM = 15.9 Newton-meters.

    6000 watts (at 100% efficiency) is equal to 8.04 HP

    Bob S
     
  8. Oct 25, 2009 #7

    Ranger Mike

    User Avatar
    Science Advisor

    Re: alternator

    be advised that in the real world alternators are 40% efficient which is why there is a difference between calculated HP and actual parasitic HP required to turn the Alt.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Force necessary to spin an alternator at the rated RPM?
  1. Force to RPM (Replies: 6)

Loading...