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//CHAPTER 8- DIRECT CURRENT MACHINES
//Example 4
disp("CHAPTER 8");
disp("EXAMPLE 4");
//VARIABLE INITIALIZATION
v_t=240; //in Volts
I_l=200; //full load current in Amperes
r_f=60; //shunt field resisatnce in Ohms
eff=90; //percentage full load efficiency
s_loss=800; //stray(iron + friction) loss in Watts
//SOLUTION
//solution (a)
p_o=v_t*I_l; //output
eff=eff/100;
p_i=p_o/eff;
tot_loss=p_i-p_o; //since input=output+loss
I_f=v_t/r_f;
I_a=I_l+I_f;
cu_loss=(I_f^2)*r_f; //copper loss
c_loss=cu_loss+s_loss; //constant loss
arm_loss=tot_loss-c_loss; //armature loss ((I_a^2)*r_a)
r_a=arm_loss/(I_a^2);
disp(sprintf("(a) The armature resisatnce is %f Ω",r_a));
//solution (b)
//for maximum efficiency, armature loss = constant loss =>(I_a^2)*r_a=c_loss
I_a=sqrt(c_loss/r_a);
disp(sprintf("(b) The load current corresponding to maximum efficiency is %f A",I_a));
//END
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