1 files changed, 20 insertions, 0 deletions
diff --git a/3760/CH4/EX4.48/Ex4_48.sce b/3760/CH4/EX4.48/Ex4_48.sce
new file mode 100644
index 000000000..2fcdb5218
--- /dev/null
+++ b/3760/CH4/EX4.48/Ex4_48.sce
@@ -0,0 +1,20 @@
+clc;
+v=230; // rated voltage of dc shunt motor
+ra=0.4; // armature circuit resistance
+rf=115; // field resistance
+n1=800; // initial speed 
+n2=1000; // final speed
+ia1=20; // armature current at n=800 rpm
+// torque at both speed is same therefore f1*ia1=f2*ia2 where f=field flux therefore
+Ea1=v-ia1*ra; // counter EMF at 800rpm
+// ia2=ia1*k where k=f1/f2 now writing Ea2(counter EMF at 1000rpm) in terms of k and finding value of k by solving quadratic equation in k whose terms are
+t1=ia1*ra*n1;
+t2=-v*n1;
+t3=Ea1*n2;
+p=[ t1 t2 t3];
+k=roots(p);
+if1=v/rf; // initial field current
+if2=if1/k(2); // final field current correponding to n=1000rpm
+rs=v/if2; // new shunt field circuit resistance
+re=rs-rf;
+printf('Resistance that must be inserted in shunt field circuit is %f ohms\n',floor(re));