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// A Texbook on POWER SYSTEM ENGINEERING
// A.Chakrabarti, M.L.Soni, P.V.Gupta, U.S.Bhatnagar
// DHANPAT RAI & Co.
// SECOND EDITION
// PART IV : UTILIZATION AND TRACTION
// CHAPTER 1: INDUSTRIAL APPLICATIONS OF ELECTRIC MOTORS
// EXAMPLE : 1.18 :
// Page number 699-700
clear ; clc ; close ; // Clear the work space and console
// Given data
V = 400.0 // Voltage of IM(V)
p = 4.0 // Number of poles
f = 50.0 // Frequency(Hz)
hp = 25.0 // Power developed(hp)
S = 0.04 // Slip
R_X_2 = 1.0/4 // Ratio of rotor resistance to standstill reactance i.e R2/X2
// Calculations
N_s = 120*f/p // Synchronous speed(rpm)
N_fl = N_s*(1-S) // Full load speed(rpm)
T_fl = hp*735.5*60/(2*%pi*N_fl*9.81) // Full-load torque(kg-m)
S_1 = 1.0 // Slip at standstill
X_R_2 = 1.0/R_X_2 // Ratio of standstill reactance to rotor resistance
T_s_fl = S_1/S*((1+(S*X_R_2)**2)/(1+(S_1*X_R_2)**2)) // T_standstill/T_fl
T_standstill = T_s_fl*T_fl // Standstill torque(kg-m)
S_instant = (N_s+N_fl)/N_s // Slip at instant of plugging
T_initial = (S_instant/S)*((1+(S*X_R_2)**2)/(1+(S_instant*X_R_2)**2))*T_fl // Initial plugging torque(kg-m)
// Results
disp("PART IV - EXAMPLE : 1.18 : SOLUTION :-")
printf("\nInitial plugging torque = %.1f kg-m", T_initial)
printf("\nTorque at standstill = %.f kg-m\n", T_standstill)
printf("\nNOTE: ERROR: Calculation mistake from full-load torque onwards. Hence, change in obtained answer from that of textbook")
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