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+// Electric Machinery and Transformers

+// Irving L kosow 

+// Prentice Hall of India

+// 2nd editiom

+

+// Chapter 9: POLYPHASE INDUCTION (ASYNCHRONOUS) DYNAMOS

+// Example 9-7

+

+clear; clc; close; // Clear the work space and console.

+

+// Given data

+P = 8 ; // Number of poles in the SCIM

+f = 60 ; // Frequency in Hz

+R_r = 0.3 ; // Rotor resistance per phase in ohm

+R_x = 0.7 ; // Added resistance in ohm/phase 

+R_r_total = R_r + R_x ; // Total resistance per phase in ohm

+X_lr = 1.08 ; // Locked rotor reactance in ohm

+S_r = 650 ; // Speed in rpm at which motor stalls

+E_lr = 112 ; // Induced voltage per phase

+

+// Calculations

+// case a

+Z_lr = R_r + %i*X_lr ; // Locked rotor impedance per phase

+Z_lr_m = abs(Z_lr);//Z_lr_m = magnitude of Z_lr in ohm

+Z_lr_a = atan(imag(Z_lr) /real(Z_lr))*180/%pi;//Z_lr_a=phase angle of Z_lr in degrees

+

+I_r = E_lr / Z_lr_m ; // Rotor current per phase

+cos_theta_r = cosd(Z_lr_a); // rotor power factor with the rotor short-circuited

+cos_theta = R_r / Z_lr_m ; // rotor power factor with the rotor short-circuited

+

+// case b

+// 1 at the end of Z_lr1 is just used for showing its different form Z_lr 

+// and for ease in calculations

+Z_lr1 = R_r_total + %i*X_lr ; // Locked rotor impedance per phase

+Z_lr1_m = abs(Z_lr1);//Z_lr1_m = magnitude of Z_lr1 in ohm

+Z_lr1_a = atan(imag(Z_lr1) /real(Z_lr1))*180/%pi;//Z_lr1_a=phase angle of Z_lr1 in degrees

+

+I_r1 = E_lr / Z_lr1_m ; // Rotor current per phase

+cos_theta_r1 = cosd(Z_lr1_a); // rotor power factor with the rotor short-circuited

+cos_theta1 = R_r_total / Z_lr1_m ; // rotor power factor with the rotor short-circuited

+

+// Display the results

+disp("Example 9-7 Solution : ");

+printf(" \n a: The locked-rotor impedance per phase is : ");

+printf(" \n    Z_lr in ohm = "),disp(Z_lr);

+printf(" \n    Z_lr = %.2f <%.1f ohm \n",Z_lr_m,Z_lr_a);

+printf(" \n    I_r = %.f A \n",I_r);

+printf(" \n    cosθ_r = cos(%.1f) = %.3f or \n    cosθ = R_r/Z_lr = %.3f",Z_lr_a,cos_theta_r,cos_theta);

+

+printf(" \n\n\n b: The locked-rotor impedance with added rotor resistance per phase is : ");

+printf(" \n    Z_lr in ohm = "),disp(Z_lr1);

+printf(" \n    Z_lr = %.2f <%.1f ohm \n",Z_lr1_m,Z_lr1_a);

+printf(" \n    I_r = %.1f A \n",I_r1);

+printf(" \n    cosθ_r = cos(%.1f) = %.3f or \n    cosθ = R_r/Z_lr = %.3f",Z_lr1_a,cos_theta_r1,cos_theta1);