How to plot a function for each frequency value?

Hello,

I am still relatively new to MATLAB. I am trying to plot a calculation result (specifically, developed torque versus slip) at each frequency, for each slip value. The calculations use two different ranges, both are given below:

Frequency varied from the value of 5 to 66 in steps of 10, which I have written in the array f = [5: 10 :66]

For each frequency value, slip is to be varied from values 1 to -0.4, with a step equal to 0.01. The array for this is s = [-0.4 : 0.01 : 1]

I have been trying to achieve this using nested for loops, but I am still having trouble. What I have so far is given below:

Any help or advice in how I can do this is much appreciated, thank you very much to all.

close all; clear all; clc;

Vn = 380;       % constant value parameters
fn = 50;
P = 2;
Rs = 10;
Rr = 6.3;
Lls = 0.04;
Llr = 0.04;
Lm = 0.42;

s = [-0.4 : 0.01 : 1];   % slip for the inverter supplied machine
f = [5 : 10 : 66];          % frequency to be varied
Vsn  = Vn / sqrt(3);
Vo = 5; % this is the applied voltage boost
c = Vsn - 5;

for i = length(f)
    a = f/fn;               % v/f control constant
    Xls = 2*pi*a*fn*Lls;    % stator reactance
    Xlr = 2*pi*a*fn*Llr;    % rotor reactance
    Xm = 2*pi*a*fn*Lm;      % magnetising reactance
    w_sync = 2*pi*a*fn;      % synchronous speed scaled to v/f control
    V = Vo + c*a;
        for j = length(s)
            Zm = 1j*Xm;         % magnetising branch impedance
            Zr = Rr/s(i) + 1j*Xlr;      % rotor impedance
            Zin = Rs + 1j*Xls + Zm*Zr/(Zm+Zr);  % input impedance
            Is(i) = V/Zin;                % stator current
            Ir = Zm/(Zm+Zr) * Is(i);        % rotor current
            IR = abs(Ir);       % absolute value of rotor current
            Te(i) = P * 3/w_sync * Rr/s(i) * IR^2; % electromagentic torque
            w_speed = (1-s(i))*w_sync;  % speed of rotation
        end
end

plot(s,Te)

Answer 1

[Star Strider]

You need to change these lines to go from 1:length( ... ):

for i = 1:length(f)
  . . . 
    for j = 1:length(s)

and this actually needs to have two subscripts:

Te(i,j) = P * 3/w_sync * Rr/s(i) * IR^2; % electromagentic torque

Ideally, you could use meshgrid and vectorise your code to make it faster, but it seems a bit complicated for that so I will leave that as an option for you to explore.