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Math Help - matlab problem

  1. #1
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    matlab problem

    Hello everyone

    i v just joined the forum and i would like u to give me some sort of help in my induction motor project
    i am using matlab to carry out the value for torque and then plot the torque Vs speed graph using matlab

    so i am given the parameters
    I2=5.42A
    R2=.8Ω

    to carry out the torque values for (rotor speeds(wr)=from 0-50rad/s)

    knowing that slip=s=0 when wr=50rad/s
    and slip=1 when wr=0

    Torque=(3/wr)*(I2^2) * {R2(1-s)/s}
    To sum up i want to produce a torque speed plot using matlab

    i suppose that i can do that using for loop
    i think that it is not hard but i am not that good in matlab

    here is my little attempt

    for I2=5.42

    for R2=.8
    for s=.02
    torque=(3/wr)*{(i2)^2}*{(r/s)*(1-s)}

    plz help!
    torqueplot
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  2. #2
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    Try This:

    Code:
    I2=5.42;
    R2=.8;
    s=.02;
    wr = 0:50;
    torque=(3./wr)*(I2^2)*(R2/s)*(1-s);
    plot(wr,torque)
    xlabel wr
    ylabel T
    title('Torque Plot')
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  3. #3
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    Well that was outstanding
    many thanks to u sir
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  4. #4
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    No problem at all. Please let me know if there is anything in the code that is unclear. I was in a hurry this morning so did not have time to add comments to help explain how plotting in MATLAB works.

    Regards Elbarto
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  5. #5
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    Sorry but I think that did not put the problem in the proper way
    In fact torque should be calculated for different speeds and slips
    (Not only different values of speed!)
    So
    given
    R2=.8ohm
    Rt=1.2ohm
    Lt=2.2ohm
    L2=3 ohm
    s = (ws-wr) / ws , where ws=synchronous speed and wr=rotor speed
    i2=formula in photo
    torque=(3./wr)*(I2^2)*(R2/s)*(1-s
    Also current cannot be one constant value
    It should be calculated accordingly to slip values, so for each slip value we should have a value for current
    To sum up , I think that we should use for loop to carry out values of slip ,corresponding speed ,and corresponding current on a range of values to create the proper plot
    If the code is correct we must end up with the graph shown in the attachment
    I will be thankful if u would help me
    Many thanks
    Attached Thumbnails Attached Thumbnails matlab problem-propper-output1.jpg   matlab problem-not-q-but-example.jpg   matlab problem-propper-output.bmp  
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  6. #6
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    If you provide some code, even if it just a simple example calculation then someone will help you create the graph in MATLAB. I say this because it is difficult to understand the equations you posted up.

    Also try to use code tags in your posts where appropriate. It makes reading code a lot easier.

    Code:
    look for the # symbol on the toolbar
    Elbarto
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  7. #7
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    elbarto
    I do appreciate ur help

    in the attachment there is a worked example to claculate the torque

    so i want to plot the torque speed graph for different values of slip ,speed and current as well


    please help me experts
    Attached Thumbnails Attached Thumbnails matlab problem-picture.jpg  
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  8. #8
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    hi
    again

    i think that i am nearly there

    here is my attempt

    vt=225;
    rt=1.2;
    f=50;
    r2=.8;
    ws=157;
    Lt=2.2;
    L2=3;
    s=2:.001:-1.2;
    wr=(1-s).*ws;
    Z=sqrt(((rt+(r2./s))^2)+((Lt+L2)^2));
    i2=vt/Z;
    torque=(3./wr)*(i2^2)*(r2/s)*(1-s);
    plot(s,torque);
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