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//===========================================================================
//chapter 7 example 18
clc;clear all;
//variable declaration
VL =400; //voltage in V
IL = 10; //current in A
//r = W1/W2
//tan(phi) = sqrt(3)*((W1-W2)/(W1+W2))
//tan(phi) = sqrt(3)*((1-(W2/W1))/(1+(W2/W1)))
//tan(phi) = sqrt(3)*((1-r)/(1+r))
//cos(phi) = 1/sec(phi) = 1/sqrt(1+(tan(phi)^2) = 1/sqrt(1+(3*((1-r)/(1+r))^2)
r = 0.5;
z = ((1-r)/(1+r))^2;
pf = 1/sqrt(1+(3*z));
phi = (acos(pf)*180/%pi);
W1 = VL*IL*cos((30*%pi/180)-(phi*%pi/180)); //wattmeter reading in W
W2 = VL*IL*cos((30*%pi/180)+(phi*%pi/180)); //wattmeter reading in W
//result
mprintf("wattmeter reading = %3.2f W", W1);
mprintf("\nwattmeter reading = %3.2f W",W2);
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