ECE 350: Electric Power and Machines A three-phase, 60 Hz, 8 pole, 50,000 HP, 14
ID: 1730404 • Letter: E
Question
ECE 350: Electric Power and Machines A three-phase, 60 Hz, 8 pole, 50,000 HP, 14 kV synchronous motor has negligible armature resistance. Test data for the generator is presented graphically below, and curve fit expressions for occ and scc have been provided. The rotational losses of the machine are 2 MW 1.8 1.7 1.6 3400 3200 3000 2600 2000 1800 600 400 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0 25 075 100 12 150 175 200 225 250 275 300 325 350 Field Amps 213001 V.(OC) 3430+I Use any computational resources at your disposal to determine the true operating point (required field current) of the motor if it is supplying a 35,000 HP load while normally excited and operating at 13.8 kV. You should employ an iterative solution, and you should submit sufficient work and documentation of your code or other form of solution methodology to enable your solution to be adequately validatedExplanation / Answer
% Code Running and working on Matlab 2018a
% Iterative method used is Newton Raphson
stopCriteria = 0.00001; % Relative error stopping criteria
initIf = 100; % Initial Field Current Assumption
diffInt = 0.01; % Differentiation Window
Answer = 13800; % Value of Voc desired
check = 1;
Vocfit = [];
itera = 1;
while(check > stopCriteria)
disp(itera); % Displaying No. of iterations
itera = itera +1;
%% Calculating Differentiation
initVoc = (sqrt(3) * 21300 * initIf / (430 + initIf) ) - Answer;
If = initIf*(1+diffInt);
Voc = (sqrt(3) * 21300 * If / (430 + If)) - Answer;
dVbydI = (Voc-initVoc) / (If-initIf);
%% Newton's Method
Ifnew = initIf - initVoc / dVbydI;
check = abs((Ifnew-initIf) / initIf) ; % Relative error calculation
Voc = sqrt(3) * 21300 * Ifnew / (430 + Ifnew); % Interim Voc
Vocfit = [Vocfit,Voc];
initIf = Ifnew; % Assign current value of If to next iteration
end
synchronousReactance = Voc/ (7*Ifnew);
disp(['The value of Field Current is = ',num2str(Ifnew),'A']);
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