COMSATS University Islamabad – Abbottabad
Campus
Department of Electrical & Computer
Engineering
Assignment No 3
NAME Registration Number
Tayyaba Nawaz FA22-EPE-007
For the course
Electric Machines
SEMESTER FALL 2024
Supervised by:
DR Faisal Khan
Part 01
Write a MATLAB to calculate and plot the torque-speed
characteristic of the Induction Motor
clear; clc; close all;
Rs = 0.5; % Stator resistance
Xs = 1; % Stator leakage reactance
Rr = 0.2; % Original rotor resistance
Xr = 0.5; % Rotor leakage reactance
Xm = 30; % Magnetizing reactance
Vs = 230; % Supply voltage (line-to-line)
Ns = 1500; % Synchronous speed (rpm)
% Calculate Thevenin equivalent parameters
Vth = Vs / sqrt(3) * (Xm / sqrt(Rs^2 + (Xs + Xm)^2));
Zth = (j*Xm*(Rs + j*Xs)) / (Rs + j*(Xs + Xm));
Rth = real(Zth);
Xth = imag(Zth);
% Define slip range and calculate synchronous angular speed
slip = linspace(0.001, 1, 100);
Ws = (2*pi*Ns)/60;
% Calculate torque for original rotor resistance
torque1 = (3 * Vth^2 * Rr ./ slip) ./ (Ws * ((Rth + Rr./slip).^2 + (Xth + Xr).^2));
% Double rotor resistance
Rr_doubled = 2*Rr;
torque2 = (3 * Vth^2 * Rr_doubled ./ slip) ./ (Ws * ((Rth + Rr_doubled./slip).^2 +
(Xth + Xr).^2));
figure;
plot(slip*Ns, torque1, 'LineWidth', 2);
hold on;
plot(slip*Ns, torque2, 'LineWidth', 2, 'LineStyle', '--');
xlabel('Speed (rpm)');
ylabel('Torque (Nm)');
title('Torque-Speed Characteristics of Induction Motor');
legend('Original Rotor Resistance', 'Doubled Rotor Resistance');
grid on;
Output
Torque-Speed Characteristics of Induction Motor
80
Original Rotor Resistance
70 Doubled Rotor Resistance
60
50
Torque (Nm)
40
30
20
10
0
0 500 1000 1500
Speed (rpm)
