DC Motor Transfer Function units

Discussion in 'Homework Help' started by onlyvin, Feb 8, 2014.

  1. onlyvin

    Thread Starter New Member

    Feb 8, 2014
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    omega/Vin = (Kt/LJ)/(s^2+R/Ls+Kt^2/LJ) -----> DC Motor

    J = 3 lbm*ft^2
    R = 5000 ohms
    L = 300 H
    Kt = 300 ft*lb/A


    I'm not sure if I have to do a unit conversion of the elements to get the correct transfer function or if I can simply plug the numbers into the function above. I know omega is in rads/sec and Vin is in volts but I'm still not sure about the next step.
     
  2. ericgibbs

    AAC Fanatic!

    Jan 29, 2010
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  3. onlyvin

    Thread Starter New Member

    Feb 8, 2014
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    If I have to do a unit conversion of J and Kt with all other variable units correct,

    J = 300 lbm*ft^2 * (1 kg/2.2046 lbm)*(1m^2/10.764 ft^2) = .1264 kg*m^2
    Kt = 300 ft lbm/A * (4.4482 N/1 lbf) = 1334.46 Nm/A

    Kt this doesn't seem like an accurate number. The physical parameters in the homework problem indicate Kt = 300 ft lb/A, I think it is missing meters (m)? Checking with professor on that.
     
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