initial commit / add all books

22 files changed, 483 insertions, 0 deletions

diff --git a/3574/CH9/EX9.1/EX9_1.png b/3574/CH9/EX9.1/EX9_1.png
new file mode 100644
index 000000000..b7aa5ceac
--- /dev/null
+++ b/3574/CH9/EX9.1/EX9_1.png
diff --git a/3574/CH9/EX9.1/EX9_1.sce b/3574/CH9/EX9.1/EX9_1.sce
new file mode 100644
index 000000000..453a97c1f
--- /dev/null
+++ b/3574/CH9/EX9.1/EX9_1.sce
@@ -0,0 +1,81 @@
+// Example 9.1

+// Determine (a) Turbine torque supplied to the alternator (b) Excitation 

+// voltage (c) Active and reactive components of apparent power (d) Power 

+// factor (e) Neglecting saturation effects, excitation voltage if the field 

+// current is reduced to 85% of its voltage in (a) (f) Turbine speed.

+// Page No. 342

+

+clc; 

+clear;

+close;

+

+// Given data

+hp=112000;                  // Power input

+n=746*3600;                 // Speed

+VT=460;                     // 3-Phase supply voltage

+Pout=112000;                // Power

+Xs=1.26;                    // Synchronous reactnace

+delta=25;                   // Power angle

+eta=0.85;                   // Percent reduction factor

+P=2;                        // Number of poles

+f=60;                       // Frequnecy

+

+// (a) Turbine torque supplied to the alternator

+T=(hp*5252)/n;

+

+// (b) Excitation voltage

+Vt=VT/sqrt(3);                 // Voltage/phase

+Ef=(Pout*Xs)/(3*Vt*sind(delta));

+

+// (c) Active and reactive components of apparent power

+// Vt=Ef-Ia*j*Xs

+// Solving for Vt-Ef

+Vt_Mag=Vt;

+Vt_Ang=0;

+Ef_Mag=Ef;

+Ef_Ang=delta;

+// 

+N01=Ef_Mag+%i*Ef_Ang;      // Ef in polar form 

+N02=Vt_Mag+%i*Vt_Ang;      // Vt in polar for

+

+N01_R=Ef_Mag*cos(-Ef_Ang*%pi/180); // Real part of complex number Ef

+N01_I=Ef_Mag*sin(Ef_Ang*%pi/180); //Imaginary part of complex number Ef

+

+N02_R=Vt_Mag*cos(-Vt_Ang*%pi/180); // Real part of complex number Vt

+N02_I=Vt_Mag*sin(Vt_Ang*%pi/180); //Imaginary part of complex number Vt

+

+FinalNo_R=N01_R-N02_R;

+FinalNo_I=N01_I-N02_I;

+FinNum=FinalNo_R+%i*FinalNo_I;

+

+// Now FinNum/Xs in polar form

+FinNum_Mag=sqrt(real(FinNum)^2+imag(FinNum)^2);         // Magnitude part

+FinNum_Ang = atan(imag(FinNum),real(FinNum))*180/%pi;   // Angle part


+Ia_Mag=FinNum_Mag/Xs;

+Ia_Ang=FinNum_Ang-90;

+

+// Computation of S=3*Vt*Ia*

+S_Mag=3*Vt_Mag*Ia_Mag;

+S_Ang=Vt_Ang+-Ia_Ang;

+

+// Polar to complex form

+S_R=S_Mag*cos(-S_Ang*%pi/180);  // Real part of complex number S

+S_I=S_Mag*sin(S_Ang*%pi/180);   // Imaginary part of complex number S

+

+// (d) Power factor

+Fp=cosd(Ia_Ang);

+

+// (e) Excitation voltage

+Efnew=eta*Ef_Mag;

+

+// (f) Turbine speed

+ns=120*f/P;

+

+// Display result on command window

+printf("\n Turbine torque supplied to the alternator  = %0.1f lb-ft ",T);

+printf("\n Excitation voltage = %0.1f V/phase ",Ef);

+printf("\n Active components of apparent power= %0.0f kW ",S_R/1000);

+printf("\n Reactive components of apparent power= %0.1f kvar lagging ",S_I/1000);

+printf("\n Power factor = %0.2f lagging ",Fp);

+printf("\n Excitation voltage new = %0.1f V/phase ",Efnew);

+printf("\n Turbine speed = %0.0f r/min ",ns);

diff --git a/3574/CH9/EX9.10/EX9_10.png b/3574/CH9/EX9.10/EX9_10.png
new file mode 100644
index 000000000..8cd2c84bd
--- /dev/null
+++ b/3574/CH9/EX9.10/EX9_10.png
diff --git a/3574/CH9/EX9.10/EX9_10.sce b/3574/CH9/EX9.10/EX9_10.sce
new file mode 100644
index 000000000..0adf55f18
--- /dev/null
+++ b/3574/CH9/EX9.10/EX9_10.sce
@@ -0,0 +1,68 @@
+// Example 9.10
+// Repeat the example 9.9 assuming 90 % leading power factor
+// Determine (a) Excitation voltage (b) Power angle (c) No load voltage, 
+// assuming the field current is not changed (d) Voltage regulation (e) No load
+// voltage if the field current is reduced to 80% of its value at rated load. 
+// Page 372
+
+clc;
+clear;
+close;
+
+// Given data
+V=4800;                     // Voltage of synchronous generator
+PF=0.900;                   // Lagging power factor
+S_Mag=1000000/3;
+Xa_Mag=13.80;               // Synchronous reactance
+Xa_Ang=90;
+Vt_Ang=0;  
+
+// (a) Excitation voltage 
+Vt=V/sqrt(3);              
+Theta=acosd(PF);                // Angle
+Ia_Magstar=S_Mag/Vt;            // Magnitude of curent
+Ia_Angstar=Theta-0;             // Angle of current
+Ia_Mag=Ia_Magstar;
+Ia_Ang=Ia_Angstar;
+
+// Ef=Vt+Ia*j*Xa
+// First compute Ia*Xa
+IaXa_Mag=Ia_Mag*Xa_Mag;
+IaXa_Ang=Ia_Ang+Xa_Ang;
+// Polar to Complex form for IaXa
+IaXa_R=IaXa_Mag*cos(-IaXa_Ang*%pi/180); // Real part of complex number
+IaXa_I=IaXa_Mag*sin(IaXa_Ang*%pi/180);  // Imaginary part of complex number
+// Vt term in polar form
+Vt_Mag=Vt;
+Vt_Ang=Vt_Ang;
+// Polar to Complex form for Vt
+Vt_R=Vt_Mag*cos(-Vt_Ang*%pi/180);      // Real part of complex number
+Vt_I=Vt_Mag*sin(Vt_Ang*%pi/180);       // Imaginary part of complex number
+// Ef in complex form
+Ef_R=IaXa_R+Vt_R;
+Ef_I=IaXa_I+Vt_I;
+Ef=Ef_R+%i*Ef_I;
+// Complex to Polar form for Ef
+Ef_Mag=sqrt(real(Ef)^2+imag(Ef)^2);        // Magnitude part
+Ef_Ang= atan(imag(Ef),real(Ef))*180/%pi;   // Angle part

+
+// (b) Power angle
+PA=Ef_Ang;
+
+// (c) No load voltage, assuming the field current is not changed 
+// From figure 9.23 (b)
+VolAxis=Vt_Mag/30;        // The scale at the given voltage axis
+Ef_loc=Ef_Mag/VolAxis;    // Location of Ef voltage
+Vnl=29*VolAxis;         // No load voltage
+
+// (d) Voltage regulation
+VR=(Vnl-Vt)/Vt*100;
+
+
+// Display result on command window
+printf("\n Excitation voltage = %0.0f V ",Ef_Mag);
+printf("\n Power angle = %0.1f deg ",PA);
+printf("\n No load voltage = %0.0f V ",Vnl);
+printf("\n Voltage regulation = %0.2f Percent ",VR);
+disp('The leading power factor resulted in a negativr voltage regulation')
+
diff --git a/3574/CH9/EX9.11/EX9_11.png b/3574/CH9/EX9.11/EX9_11.png
new file mode 100644
index 000000000..0f56c7065
--- /dev/null
+++ b/3574/CH9/EX9.11/EX9_11.png
diff --git a/3574/CH9/EX9.11/EX9_11.sce b/3574/CH9/EX9.11/EX9_11.sce
new file mode 100644
index 000000000..df7931fc9
--- /dev/null
+++ b/3574/CH9/EX9.11/EX9_11.sce
@@ -0,0 +1,39 @@
+// Example 9.11
+// Determine (a) Equivalent armature resistance (b) Synchronous reactance 
+// (c) Short-circuit ratio
+// Page 377
+
+clc;
+clear;
+close;
+
+// Given data
+Vdc=10.35;                 // DC voltage
+Idc=52.80;                 // DC current
+VOCph=240/sqrt(3);         // Open-circuit phase voltage
+ISCph=115.65;              // Short-circuit phase current
+P=50000;  
+V=240;                     // Supply voltage
+
+// (a) Equivalent armature resistance
+Rdc=Vdc/Idc;               // DC resistance
+Rgamma=Rdc/2;
+Ra=1.2*Rgamma;             // Armature resistance
+
+// (b) Synchronous reactance 
+Zs= VOCph/ISCph;          // Synchronous impedance/phase
+Xs=sqrt(Zs^2-Ra^2);
+
+// (c) Short-circuit ratio
+Sbase=P/3;                // Power/phase
+Vbase=V/sqrt(3);          // Voltage/phase
+Zbase=Vbase^2/Sbase;
+Xpu=Xs/Zbase;             // Per unit synchronous reactance
+SCR=1/Xpu;                // Short-circuit ratio
+
+
+// Display result on command window
+printf("\n Equivalent armature resistance = %0.4f Ohm ",Ra);
+printf("\n Synchronous reactance = %0.4f Ohm ",Xs);
+printf("\n Short-circuit ratio = %0.3f ",SCR);
+
diff --git a/3574/CH9/EX9.2/EX9_2.png b/3574/CH9/EX9.2/EX9_2.png
new file mode 100644
index 000000000..219a86c2d
--- /dev/null
+++ b/3574/CH9/EX9.2/EX9_2.png
diff --git a/3574/CH9/EX9.2/EX9_2.sce b/3574/CH9/EX9.2/EX9_2.sce
new file mode 100644
index 000000000..02d615f88
--- /dev/null
+++ b/3574/CH9/EX9.2/EX9_2.sce
@@ -0,0 +1,23 @@
+// Example 9.2
+// Determine (a) Speed regulation (b) Governor drop
+// Page 351
+
+clc;
+clear;
+close;
+
+// Given data
+fn1=61.2;                   // No-load frequency
+frated=60;                  // Rated requency
+deltaP=500;                 // Governor rated power
+// (a) Speed regulation
+GSR=(fn1-frated)/frated;
+
+// (b) Governor drop
+deltaF=(fn1-frated);        // Frequency difference
+GD=deltaF/deltaP;
+
+// Display result on command window
+printf("\n Speed regulation = %0.2f  ",GSR);
+printf("\n Governor drop = %0.5f Hz/kW ",GD);
+ 
diff --git a/3574/CH9/EX9.3/EX9_3.png b/3574/CH9/EX9.3/EX9_3.png
new file mode 100644
index 000000000..06da73ec1
--- /dev/null
+++ b/3574/CH9/EX9.3/EX9_3.png
diff --git a/3574/CH9/EX9.3/EX9_3.sce b/3574/CH9/EX9.3/EX9_3.sce
new file mode 100644
index 000000000..dfccb7b04
--- /dev/null
+++ b/3574/CH9/EX9.3/EX9_3.sce
@@ -0,0 +1,32 @@
+// Example 9.3
+// Determine (a) Frequency of generator A (b) Frequency of generator B 
+// (c) Frequency of bus
+// Page 358
+
+clc;
+clear;
+close;
+
+// Given data
+GSR=0.020;                   // Governor speed regulation
+Frated=60;                   // Rated frequency
+deltaPa=100;                 // Change in load (200-100 =100 KW)
+Prated=500;                  // Rated power of both generators
+       
+
+// (a) Frequency of generator A 
+deltaFa=(GSR*Frated*deltaPa)/Prated; // Change in frequency due to change in load
+Fa=Frated+deltaFa;                   // Frequency of generator A
+
+// (b) Frequency of generator B
+deltaFb=0.24;                        // Since both machines are identical
+Fb=Frated-deltaFb;
+
+// (c) Frequency of bus
+Fbus=Fb;                             // Bus frequency is frequency of generator B
+
+// Display result on command window
+printf("\n Frequency of generator A = %0.2f Hz ",Fa);
+printf("\n Frequency of generator B = %0.2f Hz ",Fb);
+printf("\n Frequency of bus = %0.2f Hz ",Fbus);
+ 
diff --git a/3574/CH9/EX9.4/EX9_4.png b/3574/CH9/EX9.4/EX9_4.png
new file mode 100644
index 000000000..1e0487052
--- /dev/null
+++ b/3574/CH9/EX9.4/EX9_4.png
diff --git a/3574/CH9/EX9.4/EX9_4.sce b/3574/CH9/EX9.4/EX9_4.sce
new file mode 100644
index 000000000..03cbf6291
--- /dev/null
+++ b/3574/CH9/EX9.4/EX9_4.sce
@@ -0,0 +1,37 @@
+// Example 9.4
+// Determine (a) Operating frequency (b) Load carried by each machine
+// Page 359
+
+clc;
+clear;
+close;
+
+// Given data
+GSR=0.0243;                  // Governor speed regulation
+Frated=60;                   // Rated frequency
+deltaPa=500;                 // Change in load for alternator A
+Prateda=500;                 // Rated power of alternator A
+deltaPb=400;                 // Change in load for alternator B
+Pratedb=300;                 // Rated power of alternator B   
+Pch=100;                     // Change is power (500-400=100 KW))            
+Pchmach=200;                 // Power difference (500-300=200 KW)    
+
+// (a) Operating frequency
+// From the curve in figure 9.17
+// GSR*Frated/Prated=deltaP/deltaP
+
+deltaF=(deltaPa-deltaPb)/548.697;   // Change in frequency
+Fbus=60.5-deltaF;
+               
+
+// (b) Load carried by each machine
+deltaPa=(deltaF*Prateda)/(GSR*Frated); // Change in power for machine A
+deltaPb=Pch-deltaPa;                   // Change in power for machine B
+Pa=Pchmach+deltaPa;
+Pb=Pchmach+deltaPb;
+
+// Display result on command window
+printf("\n Operating frequency = %0.3f Hz ",Fbus);
+printf("\n Load carried by machine A = %0.2f kW",Pa);
+printf("\n Load carried by machine B = %0.2f kW",Pb);
+ 
diff --git a/3574/CH9/EX9.5/EX9_5.png b/3574/CH9/EX9.5/EX9_5.png
new file mode 100644
index 000000000..7f57f90bf
--- /dev/null
+++ b/3574/CH9/EX9.5/EX9_5.png
diff --git a/3574/CH9/EX9.5/EX9_5.sce b/3574/CH9/EX9.5/EX9_5.sce
new file mode 100644
index 000000000..9864d5ff4
--- /dev/null
+++ b/3574/CH9/EX9.5/EX9_5.sce
@@ -0,0 +1,29 @@
+// Example 9.5
+// Determine (a) Bus frequency (b) Load on each machine
+// Page 360
+
+clc;
+clear;
+close;
+
+// Given data
+Padd=720;                    // Additional load connected
+GD=0.0008;                   // Governor droop
+f=60.2;                      // Frequency of machine
+Pbus=900;                    // Bus load
+
+// (a) Bus frequency
+deltaPa=Padd/2;        
+deltaPb=deltaPa;           // Since both machines have identical governor drops       
+deltaF=GD*deltaPa;         // Change in frequency
+Fbus=f-deltaF;
+
+// (b) Load on each machine
+Pa=(2/3)*Pbus+deltaPa;     // Load on machine A
+Pb=(1/3)*Pbus+deltaPb;     // Load on machine B
+
+// Display result on command window
+printf("\n Bus frequency = %0.2f Hz ",Fbus);
+printf("\n Load on machine A = %0.0f kW",Pa);
+printf("\n Load on machine B = %0.0f kW",Pb);
+ 
diff --git a/3574/CH9/EX9.6/EX9_6.png b/3574/CH9/EX9.6/EX9_6.png
new file mode 100644
index 000000000..c15480fb7
--- /dev/null
+++ b/3574/CH9/EX9.6/EX9_6.png
diff --git a/3574/CH9/EX9.6/EX9_6.sce b/3574/CH9/EX9.6/EX9_6.sce
new file mode 100644
index 000000000..d2a20c23b
--- /dev/null
+++ b/3574/CH9/EX9.6/EX9_6.sce
@@ -0,0 +1,42 @@
+// Example 9.6
+// Determine (a) System kilowatts (b) System frequency (c) kilowatt loads
+// carried by each machine
+// Page 361
+
+clc;
+clear;
+close;
+
+// Given data
+Pres=440;                    // Resistive load
+PF=0.8;                      // Power factor
+Pind=200;                    // Induction motor power
+Palt=210;                    // Alternator bus load
+deltaPa=70;                  // Change in load for machine A
+f=60;                        // Frequency
+deltaPb=70;                  // Change in load for machine B
+deltaPc=70;                  // Change in load for machine C
+
+// (a) System kilowatts 
+deltaPbus=Pres+PF*Pind;     // Increase in bus load
+Psys=Palt+deltaPbus;
+
+// (b) System frequency
+GDa=(60.2-f)/deltaPa;       // Governor droop for machine A
+GDb=(60.4-f)/deltaPb;       // Governor droop for machine B
+GDc=(60.6-f)/deltaPc;       // Governor droop for machine C
+// From the figure 9.18(b)
+deltaF=600/(350+175+116.6667) ;
+f2=f-deltaF;
+
+// (c) Kilowatt loads carried by each machine
+Pa2=deltaPa+350*deltaF;
+Pb2=deltaPb+175*deltaF;
+Pc2=deltaPc+116.6667*deltaF;
+
+// Display result on command window
+printf("\n System kilowatts = %0.0f kW ",Psys);
+printf("\n System frequency = %0.2f Hz",f2);
+printf("\n Kilowatt loads carried by machine A = %0.1f kW",Pa2);
+printf("\n Kilowatt loads carried by machine B = %0.1f kW",Pb2);
+printf("\n Kilowatt loads carried by machine C = %0.1f kW",Pc2); 
diff --git a/3574/CH9/EX9.7/EX9_7.png b/3574/CH9/EX9.7/EX9_7.png
new file mode 100644
index 000000000..e00dd7abe
--- /dev/null
+++ b/3574/CH9/EX9.7/EX9_7.png
diff --git a/3574/CH9/EX9.7/EX9_7.sce b/3574/CH9/EX9.7/EX9_7.sce
new file mode 100644
index 000000000..3c811616d
--- /dev/null
+++ b/3574/CH9/EX9.7/EX9_7.sce
@@ -0,0 +1,34 @@
+// Example 9.7
+// Determine (a) Active and reactive components of the bus load (b) If the 
+// power factor of generator A is 0.94 lagging, determine the reactive power
+// supplied by each machine.
+// Page 366
+
+clc;
+clear;
+close;
+
+// Given data
+Pbuspower=500;              // Power supplied
+Pind=200;                   // Induction motor power
+PF=0.852;                   // Percent power factor
+NA=2;                       // Number of alternators
+LPF=0.94;                   // Lagging power factor
+
+// (a) Active and reactive components of the bus load 
+Pbus=Pbuspower+Pind*PF;      // Active component of the bus load
+ThetaMot=acosd(PF);          // Power angle of motor
+Qbus=Pind*sind(ThetaMot);    // Reactive component the bus load
+
+// (b) Reactive power supplied by each machine
+Pa=Pbus/NA;                  // Alternator A power
+ThetaA=acosd(LPF);           // Alternator A angle
+Qa=tand(ThetaA)*Pa;          // Reactive power supplied by machine A
+Qb=Qbus-Qa;                  // Reactive power supplied by machine B                 
+
+
+// Display result on command window
+printf("\n Active component of the bus load = %0.2f kW ",Pbus);
+printf("\n Reactive component of the bus load  = %0.1f kvar",Qbus);
+printf("\n Reactive power supplied by machine A = %0.1f kvar",Qa);
+printf("\n Reactive power supplied by machine B = %0.1f kvar",Qb);
diff --git a/3574/CH9/EX9.8/EX9_8.png b/3574/CH9/EX9.8/EX9_8.png
new file mode 100644
index 000000000..72bdb8964
--- /dev/null
+++ b/3574/CH9/EX9.8/EX9_8.png
diff --git a/3574/CH9/EX9.8/EX9_8.sce b/3574/CH9/EX9.8/EX9_8.sce
new file mode 100644
index 000000000..5906bbf8d
--- /dev/null
+++ b/3574/CH9/EX9.8/EX9_8.sce
@@ -0,0 +1,30 @@
+// Example 9.8
+// Computation of per-unit impedance of a generator
+// Page 368
+
+clc;
+clear;
+close;
+
+// Given data
+P=100000;                   // Power of synchronous generator
+V=480;                      // Voltage of synchronous generator
+Ra=0.0800;                  // Resistive component
+Xs=2.3;                     // Reactive component
+
+// Computation of per-unit impedance of a generator
+Sbase=P/3;                  // Rated apparent power per phase
+Vbase=V/sqrt(3);            // Rated voltage per phase
+Zbase=Vbase^2/Sbase;        // Rated impedance
+Rpu=Ra/Zbase;               // Per unit resistance
+Xpu=Xs/Zbase;               // Per unit reactance
+
+Zpu=Rpu+%i*Xpu;             // Per unit impedance
+
+// Complex to Polar form...
+Zpu_Mag=sqrt(real(Zpu)^2+imag(Zpu)^2);       // Magnitude part
+Zpu_Ang = atan(imag(Zpu),real(Zpu))*180/%pi; // Angle part

+
+// Display result on command window
+printf("\n Per-unit impedance magnitude = %0.4f Ohm ",Zpu_Mag);
+printf("\n Per-unit impedance angle = %0.2f deg ",Zpu_Ang);
diff --git a/3574/CH9/EX9.9/EX9_9.png b/3574/CH9/EX9.9/EX9_9.png
new file mode 100644
index 000000000..a837c7d8d
--- /dev/null
+++ b/3574/CH9/EX9.9/EX9_9.png
diff --git a/3574/CH9/EX9.9/EX9_9.sce b/3574/CH9/EX9.9/EX9_9.sce
new file mode 100644
index 000000000..de0d1fd19
--- /dev/null
+++ b/3574/CH9/EX9.9/EX9_9.sce
@@ -0,0 +1,68 @@
+// Example 9.9
+// Determine (a) Excitation voltage (b) Power angle (c) No load voltage, 
+// assuming the field current is not changed (d) Voltage regulation (e) No load
+// voltage if the field current is reduced to 80% of its value at rated load. 
+// Page 369
+
+clc;
+clear;
+close;
+
+// Given data
+V=4800;                     // Voltage of synchronous generator
+PF=0.900;                   // Lagging power factor
+S_Mag=1000000/3;
+Xa_Mag=13.80;               // Synchronous reactance
+Xa_Ang=90;
+Vt_Ang=0;  
+
+// (a) Excitation voltage 
+Vt=V/sqrt(3);              
+Theta=acosd(PF);                // Angle
+Ia_Magstar=S_Mag/Vt;            // Magnitude of curent
+Ia_Angstar=Theta-0;             // Angle of current
+Ia_Mag=Ia_Magstar;
+Ia_Ang=-Ia_Angstar;
+
+// Ef=Vt+Ia*j*Xa
+// First compute Ia*Xa
+IaXa_Mag=Ia_Mag*Xa_Mag;
+IaXa_Ang=Ia_Ang+Xa_Ang;
+// Polar to Complex form for IaXa
+IaXa_R=IaXa_Mag*cos(-IaXa_Ang*%pi/180); // Real part of complex number
+IaXa_I=IaXa_Mag*sin(IaXa_Ang*%pi/180);  // Imaginary part of complex number
+// Vt term in polar form
+Vt_Mag=Vt;
+Vt_Ang=Vt_Ang;
+// Polar to Complex form for Vt
+Vt_R=Vt_Mag*cos(-Vt_Ang*%pi/180);      // Real part of complex number
+Vt_I=Vt_Mag*sin(Vt_Ang*%pi/180);       // Imaginary part of complex number
+// Ef in complex form
+Ef_R=IaXa_R+Vt_R;
+Ef_I=IaXa_I+Vt_I;
+Ef=Ef_R+%i*Ef_I;
+// Complex to Polar form for Ef
+Ef_Mag=sqrt(real(Ef)^2+imag(Ef)^2);        // Magnitude part
+Ef_Ang= atan(imag(Ef),real(Ef))*180/%pi;   // Angle part

+
+// (b) Power angle
+PA=Ef_Ang;
+
+// (c) No load voltage, assuming the field current is not changed 
+// From figure 9.23 (b)
+VolAxis=Vt_Mag/30;        // The scale at the given voltage axis
+Ef_loc=Ef_Mag/VolAxis;    // Location of Ef voltage
+Vnl=33.4*VolAxis;         // No load voltage
+
+// (d) Voltage regulation
+VR=(Vnl-Vt)/Vt*100;
+
+// (e) No load voltage if the field current is reduced to 80% 
+Vnlnew=31*VolAxis;
+
+// Display result on command window
+printf("\n Excitation voltage = %0.0f V ",Ef_Mag);
+printf("\n Power angle = %0.1f deg ",PA);
+printf("\n No load voltage = %0.0f V ",Vnl);
+printf("\n Voltage regulation = %0.0f Percent ",VR);
+printf("\n No load voltage when field current is reduced to 80 percent = %0.0f V ",Vnlnew);