diff options
Diffstat (limited to '1445/CH8')
37 files changed, 1267 insertions, 0 deletions
diff --git a/1445/CH8/EX8.1/ch8_ex_1.sce b/1445/CH8/EX8.1/ch8_ex_1.sce new file mode 100644 index 000000000..b02f8d679 --- /dev/null +++ b/1445/CH8/EX8.1/ch8_ex_1.sce @@ -0,0 +1,22 @@ +//CHAPTER 8- DIRECT CURRENT MACHINES +//Example 1 + +disp("CHAPTER 8"); +disp("EXAMPLE 1"); + +//VARIABLE INITIALIZATION +v_t=250; //terminal voltage in Volts +I_l=500; //load current in Amperes +r_a=0.04; //armature resistance in Ohms +r_f=50; //shunt field resistance in Ohms + +//SOLUTION +I_f=v_t/r_f; +I_a=I_l+I_f; +E_a=v_t+(I_a*r_a); //here E_a=emf of generator +disp(sprintf("The generated emf is %f V",E_a)); + +//END + + + diff --git a/1445/CH8/EX8.10/ch8_ex_10.sce b/1445/CH8/EX8.10/ch8_ex_10.sce new file mode 100644 index 000000000..8ecea55db --- /dev/null +++ b/1445/CH8/EX8.10/ch8_ex_10.sce @@ -0,0 +1,55 @@ +//CHAPTER 8- DIRECT CURRENT MACHINES +//Example 10 + +disp("CHAPTER 8"); +disp("EXAMPLE 10"); + +//VARIABLE INITIALIZATION +P=6; //number of poles +I=80; //current per conductor in Amperes +Z=400; //tottal number of conductors +phi=0.020; //flux per pole in Wb +N=1800; //in rpm + +//SOLUTION + +//soluion (a): for wave connected +disp("(a) For Wave connected"); + +//(i) +A=2; //A=number of parallel paths +I_a=I*A; +disp(sprintf("(i) The total current is %f A",I_a)); + +//(ii) +E_a=(phi*Z*N*P)/(60*A); +disp(sprintf("(ii) The emf is %f V",E_a)); + +//(iii) +p=E_a*I_a; +disp(sprintf("(iii) The power developed in armature is %f kW",p/1000)); +w=(2*%pi*N)/60; +T_e=p/w; +disp(sprintf("The electromagnetic torque is %f N-m",T_e)); + + +//soluion (b): for lap connected +disp("(b) For Lap connected"); + +//(i) +A=P; +I_a=I*A; +disp(sprintf("(i) The total current is %f A",I_a)); + +//(ii) +E_a=(phi*Z*N*P)/(60*A); +disp(sprintf("(ii) The emf is %f V",E_a)); + +//(iii) +p=E_a*I_a; +disp(sprintf("(iii) The power developed in armature is %f kW",p/1000)); +w=(2*%pi*N)/60; +T_e=p/w; +disp(sprintf("The electromagnetic torque is %f N-m",T_e)); + +//END diff --git a/1445/CH8/EX8.11/ch8_ex_11.sce b/1445/CH8/EX8.11/ch8_ex_11.sce new file mode 100644 index 000000000..9a2478738 --- /dev/null +++ b/1445/CH8/EX8.11/ch8_ex_11.sce @@ -0,0 +1,25 @@ +//CHAPTER 8- DIRECT CURRENT MACHINES +//Example 11 + +disp("CHAPTER 8"); +disp("EXAMPLE 11"); + +//VARIABLE INITIALIZATION +p_o=20*1000; //output in W +v_t=250; //in Volts +r_a=0.05; //aramture resistance in Ohms +r_se=0.025; //series resistance in Ohms +r_sh=100; //shunt resistance in Ohms + +//SOLUTION +I_t=p_o/v_t; +v_se=I_t*r_se; //for series winding +v_sh=v_t+v_se; //for shunt winding +I_sh=v_sh/r_sh; +I_a=I_sh+I_t; +E_a=v_t+(I_a*r_a)+v_se; +disp(sprintf("The total emf generated is %f V",E_a)); + +//END + + diff --git a/1445/CH8/EX8.12/ch8_ex_12.sce b/1445/CH8/EX8.12/ch8_ex_12.sce new file mode 100644 index 000000000..96cd57019 --- /dev/null +++ b/1445/CH8/EX8.12/ch8_ex_12.sce @@ -0,0 +1,28 @@ +//CHAPTER 8- DIRECT CURRENT MACHINES +//Example 12 + +disp("CHAPTER 8"); +disp("EXAMPLE 12"); + +//VARIABLE INITIALIZATION +P=4; //number of poles +N=750; //in rpm +r_a=0.4; //in Ohms +r_f=200; //in Ohms +Z=720; +phi=2.895*(10^6)*(10^(-8)); //in Wb (1 line=10^(-8) Wb) +r_l=10; //load resistance in Ohms +A=2; //for wave winding + +//SOLUTION +E_a=(phi*Z*N*P)/(60*A); +disp(sprintf("The induced emf is %f V",E_a)); +// E_a=v+(I_a*r_a) but I_a=I_l+I_f and I_l=v/r_l, I_f=v/r_f =>I_a=(v/r_l) + (v/r_f) +// =>E_a=v+(((v/r_l) + (v/r_f))*r_a) +// taking v common, the following equation is obtained +v=E_a/(1+(r_a/r_f)+(r_a/r_l)); +disp(sprintf("The terminal voltage of the machine is %f V",v)); + +//The answer is slightly different due to the precision of floating point numbers + +//END diff --git a/1445/CH8/EX8.13/ch8_ex_13.sce b/1445/CH8/EX8.13/ch8_ex_13.sce new file mode 100644 index 000000000..a9f1555de --- /dev/null +++ b/1445/CH8/EX8.13/ch8_ex_13.sce @@ -0,0 +1,30 @@ +//CHAPTER 8- DIRECT CURRENT MACHINES +//Example 13 + +disp("CHAPTER 8"); +disp("EXAMPLE 13"); + +//VARIABLE INITIALIZATION +P=4; //number of poles +v_t=220; //in Volts +I_l=42; //load current in Amperes +r_a=0.1; //in Ohms +r_f=110; //in Ohms +drop=1; //contact drop per brush +//SOLUTION + +//solution (i) +A=P; //for lap winding +I_f=v_t/r_f; //I_f is same as I_sh +I_a=I_l+I_f; +I_c=I_a/A; //conductor current +disp(sprintf("The current in each conductor of the armature is %d A",I_c)); + +//solution (ii) +v_a=I_a*r_a; //armature voltage drop +v_b=2*drop; //brush drop +emf=v_t+v_a+v_b; +disp(sprintf("The total emf generated is %f V",emf)); + +//END + diff --git a/1445/CH8/EX8.14/ch8_ex_14.sce b/1445/CH8/EX8.14/ch8_ex_14.sce new file mode 100644 index 000000000..2dedf26ce --- /dev/null +++ b/1445/CH8/EX8.14/ch8_ex_14.sce @@ -0,0 +1,33 @@ +//CHAPTER 8- DIRECT CURRENT MACHINES +//Example 14 + +disp("CHAPTER 8"); +disp("EXAMPLE 14"); + +//VARIABLE INITIALIZATION +v_t=220; //in Volts +I_l=196; //in Amperes +s_loss=720; //stray loss in Watts +r_f=55; //shunt field ressitance in Ohms +eff=88/100; //efficiency + +//SOLUTION +p_o=v_t*I_l; +p_i=p_o/eff; //electrical input +tot_loss=p_i-p_o; +I_f=v_t/r_f; +I_a=I_l+I_f; +cu_loss=v_t*I_f; //shunt field copper loss +c_loss=cu_loss+s_loss; //constant loss +arm_loss=tot_loss-c_loss; //armature copper loss +r_a=arm_loss/(I_a^2); +disp(sprintf("The armature resistance is %f Ω",r_a)); + +//for maximum efficiency, armature loss = constant loss =>(I_a^2)*r_a=c_loss +I_a=sqrt(c_loss/r_a); +disp(sprintf("The load current corresponding to maximum efficiency is %f A",I_a)); + +//END + + + diff --git a/1445/CH8/EX8.15/ch8_ex_15.sce b/1445/CH8/EX8.15/ch8_ex_15.sce new file mode 100644 index 000000000..e7909058b --- /dev/null +++ b/1445/CH8/EX8.15/ch8_ex_15.sce @@ -0,0 +1,30 @@ +//CHAPTER 8- DIRECT CURRENT MACHINES +//Example 15 + +disp("CHAPTER 8"); +disp("EXAMPLE 15"); + +//VARIABLE INITIALIZATION +v_t=230; //in Volts +I_a1=3.33; //in Amperes +N1=1000; //in rpm +r_a=0.3; //armature resistance in Ohms +r_f=160; //field resistance in Ohms +I_l=40; //in Amperes +phi1=1; //in Wb (phi=1 is an assumption) +phi2=(1-(4/100)); //in Wb (phi2=0.96 of phi1) + +//SOLUTION + +//At no load +E_a1=v_t-(I_a1*r_a); +I_f=v_t/r_f; + +//At full load +I_a2=I_l-I_f; +E_a2=v_t-(I_a2*r_a); +N2=(E_a2/E_a1)*(phi1/phi2)*N1; +N2=round(N2); //to round off the value +disp(sprintf("The full load speed is %d rpm",N2)); + +//END diff --git a/1445/CH8/EX8.16/ch8_ex_16.sce b/1445/CH8/EX8.16/ch8_ex_16.sce new file mode 100644 index 000000000..ef76b6ef8 --- /dev/null +++ b/1445/CH8/EX8.16/ch8_ex_16.sce @@ -0,0 +1,45 @@ +//CHAPTER 8- DIRECT CURRENT MACHINES +//Example 16 + +disp("CHAPTER 8"); +disp("EXAMPLE 16"); + +//VARIABLE INITIALIZATION +v_t=250; //in Volts +P=4; //number of poles +Z=500; //number of conductors +r_a=0.25; //in Ohms +r_f=125; //in Ohms +phi=0.02; //in Wb +I_l=14; //in Amperes +A=2; +rot_loss=300; //rotational loss in Watts + +//SOLUTION + +//solution (i) +I_f=v_t/r_f; +I_a=I_l-I_f; +E_a=v_t-(I_a*r_a); +N=(E_a*A*60)/(phi*Z*P); +N=round(N); //to round off the value of N +disp(sprintf("(i) The speed is %d rpm",N)); +p_e=E_a*I_a; +w=(2*%pi*N)/60; +T1=p_e/w; +disp(sprintf("The internal torque developed is %f N-m",T1)); + +//solution (ii) +p_o=p_e-rot_loss; +disp(sprintf("(ii)The shaft power is %f W",p_o)); +T2=p_o/w; +disp(sprintf("The shaft torque is %f N-m",T2)); +p_i=v_t*I_l; +eff=(p_o/p_i)*100; +disp(sprintf("The efficiency is %f %%",eff)); + +//END + + + + diff --git a/1445/CH8/EX8.17/ch8_ex_17.sce b/1445/CH8/EX8.17/ch8_ex_17.sce new file mode 100644 index 000000000..d2c9b4413 --- /dev/null +++ b/1445/CH8/EX8.17/ch8_ex_17.sce @@ -0,0 +1,44 @@ +//CHAPTER 8- DIRECT CURRENT MACHINES +//Example 17 + +disp("CHAPTER 8"); +disp("EXAMPLE 17"); + +//VARIABLE INITIALIZATION +v_t=200; //in Volts +I_l=22; //in Amperes +N1=1000; //in rpm +r_a=0.1; //in Ohms +r_f=100; //in Ohms +N2=800; //in rpm + +//SOLUTION + +//solution (i) +I_f=v_t/r_f; +I_a1=I_l-I_f; +E_a1=v_t-(I_a1*r_a); +//on rearranging the equation E_a2:E_a1=N2:N1, where E_a2=v_t-I_a1*(r_a+r_s) and E_a1=v_t-(I_a1*r_a), we get, +r_s1=((v_t - ((N2*E_a1)/N1))/I_a1)-r_a; +disp(sprintf("(i) When the load torque is independent of speed, the additional resistance is %f Ω",r_s1)); + +//solution (ii) +I_a2=(N2/N1)*I_a1; +//on rearranging the equation E_a2:E_a1=N2:N1, where E_a2=v_t-I_a2*(r_a+r_s) and E_a1=v_t-(I_a1*r_a), we get, +r_s2=((v_t - ((N2*E_a1)/N1))/I_a2)-r_a; +disp(sprintf("(ii)When the load torque is proportional to speed, the additional resistance is %f Ω",r_s2)); + +//solution (iii) +I_a2=(N2^2/N1^2)*I_a1; +//on rearranging the equation E_a2:E_a1=N2:N1, where E_a2=v_t-I_a2*(r_a+r_s) and E_a1=v_t-(I_a1*r_a), we get, +r_s3=((v_t - ((N2*E_a1)/N1))/I_a2)-r_a; +disp(sprintf("(iii)When the load torque varies as the square of speed, the additional resistance is %f Ω",r_s3)); + +//solution (iv) +I_a2=(N2^3/N1^3)*I_a1; +//on rearranging the equation E_a2:E_a1=N2:N1, where E_a2=v_t-I_a2*(r_a+r_s) and E_a1=v_t-(I_a1*r_a), we get, +r_s4=((v_t - ((N2*E_a1)/N1))/I_a2)-r_a; +disp(sprintf("(iv)When the load torque varies as the cube of speed, the additional resistance is %f Ω",r_s4)); + +//END + diff --git a/1445/CH8/EX8.18/ch8_ex_18.sce b/1445/CH8/EX8.18/ch8_ex_18.sce new file mode 100644 index 000000000..ba0966842 --- /dev/null +++ b/1445/CH8/EX8.18/ch8_ex_18.sce @@ -0,0 +1,28 @@ +//CHAPTER 8- DIRECT CURRENT MACHINES +//Example 18 + +disp("CHAPTER 8"); +disp("EXAMPLE 18"); + +//VARIABLE INITIALIZATION +v_t=460; //in Volts +p_o=10*736; //in Watts (1 metric H.P=735.5 W) +ratio=85/100; //as given in the question +eff=84/100; +I_f=1.1; //in Amperes +r_a=0.2; //in Ohms + +//SOLUTION +p_i=p_o/eff; +I_l=p_i/v_t; +I_a=I_l-I_f; +E1=v_t-(I_a*r_a); +E2=E1*ratio; //E2:E1=N2:N1=ratio +v=v_t-E2; //voltage drop across r_a and r_s (r_s is the series resistance to be inserted) +r_s=(v/I_a)-r_a; +disp(sprintf("The resistance required is %f Ω",r_s)); + +//The answer is different because ratio equals 85/100 and not 75/100 + +//END + diff --git a/1445/CH8/EX8.19/ch8_ex_19.sce b/1445/CH8/EX8.19/ch8_ex_19.sce new file mode 100644 index 000000000..66ce6423f --- /dev/null +++ b/1445/CH8/EX8.19/ch8_ex_19.sce @@ -0,0 +1,32 @@ +//CHAPTER 8- DIRECT CURRENT MACHINES +//Example 19 + +disp("CHAPTER 8"); +disp("EXAMPLE 19"); + +//VARIABLE INITIALIZATION +v_t=250; //in Volts +r_a=0.5; //in Ohms +r_f=250; //in Ohms +N1=600; //in rpm +I=21; //in Amperes +r_s=250; //in Ohms + +//SOLUTION +I_f1=v_t/r_f; +I_f2=v_t/(r_f+r_s); +I_a1=I-I_f1; +// T is directly proportional to (Φ*I_a) +// I_f is directly proportional to Φ +// => I_f1*I_a1=I_f2*I_a2, therefore, +I_a2=(I_f1*I_a1)/I_f2; +E_b1=v_t-(I_a1*r_a); +E_b2=v_t-(I_a2*r_a); +// E_b is directly proportional to (Φ*N) +// (Φ*N) is directly proportinal to (I_f*N) +// =>E_b1:E_b2=(I_f1:I_f2)*(N1:N2) +N2=(I_f1/I_f2)*(E_b2/E_b1)*N1; +N2=round(N2); //to round off the value +disp(sprintf("The new speed of the motor is %d rpm",N2)); + +//END diff --git a/1445/CH8/EX8.2/ch8_ex_2.sce b/1445/CH8/EX8.2/ch8_ex_2.sce new file mode 100644 index 000000000..c1c419419 --- /dev/null +++ b/1445/CH8/EX8.2/ch8_ex_2.sce @@ -0,0 +1,29 @@ +//CHAPTER 8- DIRECT CURRENT MACHINES +//Example 2 + +disp("CHAPTER 8"); +disp("EXAMPLE 2"); + +//VARIABLE INITIALZATION +v_t=230; //terminal voltage in Volts +r_a=0.5; //armature resistance in Ohms +r_f=115; //shunt field resistance in Ohms +I_l=40; //line current in Amperes + +//SOLUTION + +//for generator +I_f=v_t/r_f; +I_a=I_l+I_f; +E_a=v_t+(I_a*r_a); //here E_a=emf of generator + +//for motor +I_f=v_t/r_f; +I_a=I_l-I_f; +E_b=v_t-(I_a*r_a); //here E_b=emf of motor + +ratio=E_a/E_b; //E_a:E_b=(k_a*flux*N_g):(k_a*flux*N_m) =>E_a:E_b=N_g:N_m (as flux is constant) +disp(sprintf("The ratio of speed as a generator to the speed as a motor i.e. N_g:N_m is %f",ratio)); + +//END + diff --git a/1445/CH8/EX8.20/ch8_ex_20.sce b/1445/CH8/EX8.20/ch8_ex_20.sce new file mode 100644 index 000000000..54ce57258 --- /dev/null +++ b/1445/CH8/EX8.20/ch8_ex_20.sce @@ -0,0 +1,34 @@ +//CHAPTER 8- DIRECT CURRENT MACHINES +//Example 20 + +disp("CHAPTER 8"); +disp("EXAMPLE 20"); + +//VARIABLE INITIALIZATION +v_t=250; //in Volts +I_a1=20; //in Amperes +N1=1000; //in rpm +r_a=0.5; //in Ohms +drop=1; //brush contact drop in Volts +ratio=1.5; //N2:N1=1.5 +phi1=1; //it is an assumption + +//SOLUTION +E_1=v_t-(I_a1*r_a)-(2*drop); +//solving the quadratic equation directly, +a=1; +b=-496; +c=14280; +D=b^2-(4*a*c); +x1=(-b+sqrt(D))/(2*a); +x2=(-b-sqrt(D))/(2*a); +if(x1<40) +I_a2=x1; +else if(x2<40) +I_a2=x2; +end; +phi2=(I_a1/I_a2)*phi1; +phi=(1-phi2)*100; +disp(sprintf("The flux to be reduced is %f %% of the main flux",phi)); + +//END diff --git a/1445/CH8/EX8.21/ch8_ex_21.sce b/1445/CH8/EX8.21/ch8_ex_21.sce new file mode 100644 index 000000000..81ba71e3b --- /dev/null +++ b/1445/CH8/EX8.21/ch8_ex_21.sce @@ -0,0 +1,36 @@ +//CHAPTER 8- DIRECT CURRENT MACHINES +//Example 21 + +disp("CHAPTER 8"); +disp("EXAMPLE 21"); + +//VARIABLE INITIALIZATION +p_o=10*1000; //in Watts +P=6; //number of poles +E_g=200; //in Volts +N=1500; //in rpm +A=P; //since the armature is lap connected +B=0.9; //flux density in Tesla +l=0.25; //length of armature in m +dia=0.2; //diameter of armature in m + +//SOLUTION + +//solution (a) +area=2*%pi*(dia/2)*l; +phi=B*area; +disp(sprintf("(a) The flux per pole is %f Wb",phi)); + +//solution (b) +Z=(60*E_g)/(phi*N); +disp(sprintf("(b) The total number of active conductors is %d",Z)); + +//solution (c) +I_a=50; +p=E_g*I_a; +w=(2*%pi*N)/60; +T=p/w; +disp(sprintf("(c) The torque developed when armature current is 50 A is %f N-m",T)); + +//END + diff --git a/1445/CH8/EX8.22/ch8_ex_22.sce b/1445/CH8/EX8.22/ch8_ex_22.sce new file mode 100644 index 000000000..6864da4e0 --- /dev/null +++ b/1445/CH8/EX8.22/ch8_ex_22.sce @@ -0,0 +1,46 @@ +//CHAPTER 8- DIRECT CURRENT MACHINES +//Example 22 + +disp("CHAPTER 8"); +disp("EXAMPLE 22"); + +//VARIABLE INITIALIZATION +N1=600; //in rpm +v=230; //in Volts +I_l1=50; //line current in Amperes +r_a=0.4; //armature resistance in Ohms +r_f=104.5; //field resistance in Ohms +drop=2; //brush drop in Volts + +//SOLUTION + +//solution (i) +I_l2=5; +I_a1=I_l1-(v/r_f); +E_b1=v-(I_a1*r_a)-drop; +I_a2=I_l2-(v/r_f); +E_b2=v-(I_a2*r_a)-drop; +N2=(E_b2/E_b1)*N1; +N2=round(N2); +disp(sprintf("(i) The speed at no load is %d rpm",N2)); + +//solution (ii) +I_l2=50; +N2=500; +E_b2=(N2/N1)*E_b1; +dif=v-drop; //difference +I_a2=I_l2-(v/r_f); +r_se=((dif-E_b2)/I_a2)-r_a; +disp(sprintf("(ii) The additional resistance is %f Ω",r_se)); + +//solution (iii) +phi1=1; //it is an assumption +I_a3=30; +N2=750; +E_b3=v-(I_a3*r_a)-drop; +phi2=(E_b3/E_b1)*(N1/N2)*phi1; +red=((1-phi2)*100*phi1)/phi1; +disp(sprintf("(iii) The percentage reduction of flux per pole is %f %%",red)); + +//END + diff --git a/1445/CH8/EX8.23/ch8_ex_23.sce b/1445/CH8/EX8.23/ch8_ex_23.sce new file mode 100644 index 000000000..55b53553d --- /dev/null +++ b/1445/CH8/EX8.23/ch8_ex_23.sce @@ -0,0 +1,25 @@ +//CHAPTER 8- DIRECT CURRENT MACHINES +//Example 23 + +disp("CHAPTER 8"); +disp("EXAMPLE 23"); + +//VARIABLE INITIALIZATION +v=230; //in Volts +r_a=0.4; //in Ohms +r_f1=115; //in Ohms +I_a=20; //in Amperes +N1=800; //in rpm +N2=1000; //in rpm + +//SOLUTION +I_f1=v/r_f1; //redundant step +E_b1=v-(I_a*r_a); +//rearranging the equation, we get, +r_f2=((E_b1*N2)/((v*N1)-(N1*I_a*r_a)))*r_f1; +r_f2_dash=r_f2-r_f1; +disp(sprintf("The external resistance is %f Ω",r_f2_dash)); + +//The answer is slightly different due to the precision of floating point numbers + +//END diff --git a/1445/CH8/EX8.24/ch8_ex_24.sce b/1445/CH8/EX8.24/ch8_ex_24.sce new file mode 100644 index 000000000..e330f4a03 --- /dev/null +++ b/1445/CH8/EX8.24/ch8_ex_24.sce @@ -0,0 +1,28 @@ +//CHAPTER 8- DIRECT CURRENT MACHINES +//Example 24 + +disp("CHAPTER 8"); +disp("EXAMPLE 24"); + +//This example is same as example 19 + +//VARIABLE INITIALIZATION +v=250; //in Volts +r_a=0.5; //in Ohms +r_f=250; //in Ohms +N1=600; //in rpm +I_l=21; //in Amperes +r=250; //in Ohms + +//SOLUTION +I_f1=v/r_f; +I_a1=I_l-I_f1; +I_a2=2*I_a1; +E_b1=v-(I_a1*r_a); +E_b2=v-(I_a2*r_a); +ratio=(r+r_f)/r_f; +N2=(ratio*N1*E_b2)/E_b1; +N2=round(N2); +disp(sprintf("The new speed is %d rpm",N2)); + +//END diff --git a/1445/CH8/EX8.25/ch8_ex_25.sce b/1445/CH8/EX8.25/ch8_ex_25.sce new file mode 100644 index 000000000..8ab814ab4 --- /dev/null +++ b/1445/CH8/EX8.25/ch8_ex_25.sce @@ -0,0 +1,44 @@ +//CHAPTER 8- DIRECT CURRENT MACHINES +//Example 25 + +disp("CHAPTER 8"); +disp("EXAMPLE 25"); + + +//VARIABLE INITIALIZATION +slot=24; //number of slots +P=2; //number of poles +N=18; //number of turns per coil +B=1; //in Webers +l=20/100; //effective length in meters +rad=10/100; //radius in meters +w=183.2; //angular velocity in rad/s + +//SOLUTION +A=2; +Z=slot*P*N; //total number of conductors +ar1=(2*%pi*rad*l)/P; +ar2=ar1*0.8; //since the magnetic poles 80% of the armature periphery +phi=B*ar2; //effective flux per pole + +//solution (a) +E_a=(P*Z*phi*w)/(2*%pi*A); +disp(sprintf("(a) The induced emf is %f V",E_a)); + +//solution (b) +coil=slot/P; //number of coils in each path +E_coil=E_a/coil; +disp(sprintf("(b) The induced emf per coil is %f V",E_coil)); + +//solution (c) +E_turn=E_coil/N; +disp(sprintf("(c) The induced emf per turn is %f V",E_turn)); + +//solution (d) +E_cond=E_turn/A; +disp(sprintf("(d) The induced emf per conductor is %f V",E_cond)); + +//The answers are slightly different due to the precision of floating point numbers + +//END + diff --git a/1445/CH8/EX8.27/ch8_ex_27.sce b/1445/CH8/EX8.27/ch8_ex_27.sce new file mode 100644 index 000000000..1c74876c6 --- /dev/null +++ b/1445/CH8/EX8.27/ch8_ex_27.sce @@ -0,0 +1,27 @@ +//CHAPTER 8- DIRECT CURRENT MACHINES +//Example 27 + +disp("CHAPTER 8"); +disp("EXAMPLE 27"); + + +//VARIABLE INITIALIZATION +v_t=200; //in volts +r_a=0.06; //in Ohms +r_se=0.04; //in Ohms +p_i=20*1000; //in Watts + +//SOLUTION + +//solution (a) +I_a=p_i/v_t; +E_b=v_t-I_a*(r_a+r_se); +disp(sprintf("(a) The counter emf of the motor is %d V",E_b)); + +//solution (b) +p_a=E_b*I_a; +p_a=p_a/1000; //from W to kW +disp(sprintf("(b) The power developed in the armature is %d kW",p_a)); + +//END + diff --git a/1445/CH8/EX8.28/ch8_ex_28.sce b/1445/CH8/EX8.28/ch8_ex_28.sce new file mode 100644 index 000000000..318634584 --- /dev/null +++ b/1445/CH8/EX8.28/ch8_ex_28.sce @@ -0,0 +1,24 @@ +//CHAPTER 8- DIRECT CURRENT MACHINES +//Example 28 + +disp("CHAPTER 8"); +disp("EXAMPLE 28"); + +//VARIABLE INITIALIZATION +E_a=120; //in Volts +r_se=0.03; //in Ohms +r_a=0.02; //in Ohms +v1=240; //in Volts +r=0.25; //in Ohms +I=300; //in Amperes + +//SOLUTION +v=I*(r_se+r_a+r); +disp(sprintf("The voltage drop across the three resistances is %d V",v)); +v_t=v1+E_a-v; +disp(sprintf("The voltage between far end and the bus bar is %d V",v_t)); +disp(sprintf("The net increase of %d V may be beyond the desired limit",v_t-v1)); +disp("Hence, a field diverter resistance may be necessary to regulate the far-end terminal voltage"); + +//END + diff --git a/1445/CH8/EX8.29/ch8_ex_29.sce b/1445/CH8/EX8.29/ch8_ex_29.sce new file mode 100644 index 000000000..ee4e53e7d --- /dev/null +++ b/1445/CH8/EX8.29/ch8_ex_29.sce @@ -0,0 +1,21 @@ +//CHAPTER 8- DIRECT CURRENT MACHINES +//Example 29 + +disp("CHAPTER 8"); +disp("EXAMPLE 29"); + +//VARIABLE INITIALIZATION +r_a=1; //in Ohms +N1=800; //in rpm +v_t=200; //in Volts +I_a=15; //in Amperes +r_s=5; //series resistance in Ohms + +//SOLUTION +E_b1=v_t-(I_a*r_a); +E_b2=v_t-I_a*(r_a+r_s); +N2=(E_b2/E_b1)*N1; +N2=round(N2); //to round off the value +disp(sprintf("The speed attained after connecting the series resistance is %d rpm",N2)); + +//END diff --git a/1445/CH8/EX8.3/ch8_ex_3.sce b/1445/CH8/EX8.3/ch8_ex_3.sce new file mode 100644 index 000000000..198d7214a --- /dev/null +++ b/1445/CH8/EX8.3/ch8_ex_3.sce @@ -0,0 +1,38 @@ +//CHAPTER 8- DIRECT CURRENT MACHINES +//Example 3 + +disp("CHAPTER 8"); +disp("EXAMPLE 3"); + +//VARIABLE INITIALIZATION +p_o=10*1000; //output of generator in Watts +v_t=250; //terminal voltage in Volts +N=1000; //speed in rpm +r_a=0.15; //armature resistance in Ohms +I_f=1.64; //field current in Amperes +rot_loss=540; //rotational loss in Watts + +//SOLUTION + +//solution (i) +I_l=p_o/v_t; +I_a=I_l+I_f; +E_a=v_t+(I_a*r_a); +disp(sprintf("(i) The armature induced emf is %f V",E_a)); + +//solution (ii) +w=(2*%pi*N)/60; //in radian/sec +T_e=(E_a*I_a)/w; +disp(sprintf("(ii) The torque developed is %f N-m",T_e)); + +//solution (iii) +arm_loss=(I_a^2)*r_a; //armature loss +fld_loss=v_t*I_f; //field loss +tot_loss=rot_loss+arm_loss+fld_loss; +p_i=p_o+tot_loss; +eff=(p_o/p_i)*100; +disp(sprintf("(iii) The efficiency is %f %%",eff)); + +//END + + diff --git a/1445/CH8/EX8.30/ch8_ex_30.sce b/1445/CH8/EX8.30/ch8_ex_30.sce new file mode 100644 index 000000000..3c80b3dd7 --- /dev/null +++ b/1445/CH8/EX8.30/ch8_ex_30.sce @@ -0,0 +1,20 @@ +//CHAPTER 8- DIRECT CURRENT MACHINES +//Example 30 + +disp("CHAPTER 8"); +disp("EXAMPLE 30"); + +//VARIABLE INITIALIZATION +p=5*735.5; //in Watts (1 metric H.P.=735.5 W) +N=1000; //in rpm +I=30; //in Amperes +I_s=45; //starting current in Amperes + +//SOLUTION +T=(p*60)/(2*%pi*1000); +T_s=(T*(I_s^2))/(I^2); +disp(sprintf("The starting torque is %f N-m",T_s)); + +//The answer is slightly different due to precision of floating point numbers + +//END diff --git a/1445/CH8/EX8.31/ch8_ex_31.sce b/1445/CH8/EX8.31/ch8_ex_31.sce new file mode 100644 index 000000000..0fc0fecfb --- /dev/null +++ b/1445/CH8/EX8.31/ch8_ex_31.sce @@ -0,0 +1,26 @@ +//CHAPTER 8- DIRECT CURRENT MACHINES +//Example 31 + +disp("CHAPTER 8"); +disp("EXAMPLE 31"); + +//VARIABLE INITIALIZATION +r_a=0.1; //combined resistance of armature & field resistance in Ohms +v_t=230; //in Volts +I_a1=100; //in Amperes +N1=1000; //in rpm +I_a2=200; //in Amperes +ratio=1.2; //ratio of Φ2:Φ1=1.2 + +//SOLUTION +E_b1=v_t-(I_a1*r_a); //numerator of LHS according to the book +E_b2=v_t-(I_a2*r_a); //denominator of LHS according to the book +N2=(E_b2/E_b1)*(1/ratio)*N1; +N2=round(N2); //to round off the value +disp(sprintf("The new speed of the armature is %d rpm",N2)); + +//END + + + + diff --git a/1445/CH8/EX8.32/ch8_ex_32.sce b/1445/CH8/EX8.32/ch8_ex_32.sce new file mode 100644 index 000000000..e072ece81 --- /dev/null +++ b/1445/CH8/EX8.32/ch8_ex_32.sce @@ -0,0 +1,66 @@ +//CHAPTER 8- DIRECT CURRENT MACHINES +//Example 32 + +disp("CHAPTER 8"); +disp("EXAMPLE 32"); + +//VARIABLE INITIALIZATION +v_t=250; //in Volts +I=20; //in Amperes +N1=1000; //in rpm +P=4; //number of poles +r_p=0.05; //resistance of field coil on each pole in Ohms +r_a=0.2; //in Ohms + +//SOLUTION + +r_se=P*r_p; +r_m=r_a+r_se; //resistance of motor +E_b1=v_t-(I*r_m); +T1=I^2; + +//solution (a) +//solving the quadratic equation directly, +r=10; //in Ohms +a=1.02; +b=-25; +c=-400; +D=b^2-(4*a*c); +x1=(-b+sqrt(D))/(2*a); +x2=(-b-sqrt(D))/(2*a); +//to extract the positive root out of the two +if (x1>0 & x2<0) +I1=x1; +else (x1<0 & x2>0) +I1=x2; +end; +I_a=((10.2*I1)-v_t)/r; +E_b2=v_t-(I_a*r_a); +N2=((E_b2/E_b1)*I*N1)/I1; +N2=round(N2); //to round off the value +disp(sprintf("(a) The speed with 10 Ω resistance in parallel with the armature is %d rpm",N2)); + +//solution (b) +//solving the quadratic equation directly, +a=5/7; +b=0; +c=-400; +D=b^2-(4*a*c); +y1=(-b+sqrt(D))/(2*a); +y2=(-b-sqrt(D))/(2*a); +//to extract the positive root out of the two +if (y1>0 & y2<0) +I2=y1; +else (y1<0 & y2>0) +I2=y2; +end; +E_b3=v_t-(I2*r_a); +N3=((E_b3/E_b1)*I*N1)/(I2*a); +N3=round(N3); //to round off the value +disp(sprintf("(b) The speed with 0.5 Ω resistance in parallel with series field is %d rpm",N3)); + +//The answers are slightly different due to the precision of floating point numbers + +//END + + diff --git a/1445/CH8/EX8.33/ch8_ex_33.sce b/1445/CH8/EX8.33/ch8_ex_33.sce new file mode 100644 index 000000000..28ccd4097 --- /dev/null +++ b/1445/CH8/EX8.33/ch8_ex_33.sce @@ -0,0 +1,30 @@ +//CHAPTER 8- DIRECT CURRENT MACHINES +//Example 33 + +disp("CHAPTER 8"); +disp("EXAMPLE 33"); + +//VARIABLE INITIALIZATION +v_t=230; //in Volts +N1=1500; //in rpm +I_a1=20; //in Amperes +r_a=0.3; //armature resistance in Ohms +r_se=0.2; //series field resistance in Ohms + +//SOLUTION + +//solution (a) +E_b=0; //at starting +nr1=v_t-I_a1*(r_a+r_se); //value of numerator +r_ext=nr1/I_a1; +disp(sprintf("(a) At starting, the resistance that must be added is %f Ω",r_ext)); + +//solution (b) +I_a2=I_a1; +N2=1000; +ratio=N2/N1; +nr2=v_t-I_a2*(r_a+r_se); +r_ext=((ratio*nr1)-nr2)/(-I_a2); +disp(sprintf("(b) At 1000 rpm, the resistance that must be added is %f Ω",r_ext)); + +//END diff --git a/1445/CH8/EX8.34/ch8_ex_34.sce b/1445/CH8/EX8.34/ch8_ex_34.sce new file mode 100644 index 000000000..4695c56c7 --- /dev/null +++ b/1445/CH8/EX8.34/ch8_ex_34.sce @@ -0,0 +1,30 @@ +//CHAPTER 8- DIRECT CURRENT MACHINES +//Example 34 + +disp("CHAPTER 8"); +disp("EXAMPLE 34"); + +//VARIABLE INITIALIZATION +r_a=0.06; //armature resistance in Ohms +r_se=0.04; //series resistance in Ohms +r_sh=25; //shunt resistance in Ohms +v_t=110; //in Volts +I_l=100; //in Amperes + +//SOLUTION + +//solution (a) +I_sh=v_t/r_sh; +I_a=I_sh+I_l; +E_g=v_t+I_a*(r_a+r_se); +disp("(a) When the machine is connected as long shunt compound generator-"); +disp(sprintf("The armature current is %f A and the total emf is %f V",I_a,E_g)); + +//solution (b) +I_sh=(v_t/r_sh)+(I_l*r_se/r_sh); +I_a=I_sh+I_l; +E_g=v_t+(I_a*r_a)+(I_l*r_se); +disp("(b) When the machine is connected as short shunt compound generator-"); +disp(sprintf("The armature current is %f A and the total emf is %f V",I_a,E_g)); + +//END diff --git a/1445/CH8/EX8.35/ch8_ex_35.sce b/1445/CH8/EX8.35/ch8_ex_35.sce new file mode 100644 index 000000000..e387ab83e --- /dev/null +++ b/1445/CH8/EX8.35/ch8_ex_35.sce @@ -0,0 +1,30 @@ +//CHAPTER 8- DIRECT CURRENT MACHINES +//Example 35 + +disp("CHAPTER 8"); +disp("EXAMPLE 35"); + +//VARIABLE INITIALIZATION +r_a=0.06; //armature resistance in Ohms +r_se=0.04; //series resistance in Ohms +r_sh=25; //shunt resistance in Ohms +v_t=110; //in Volts +I_l=100; //in Amperes + +//SOLUTION + +//solution (a) +I_sh=v_t/r_sh; +I_a=I_l-I_sh; +E_g=v_t-I_a*(r_a+r_se); +disp("(a) When the machine is connected as long shunt compound generator-"); +disp(sprintf("The armature current is %f A and the total emf is %f V",I_a,E_g)); + +//solution (b) +I_sh=(v_t/r_sh)-(I_l*r_se/r_sh); +I_a=I_l-I_sh; +E_g=v_t-(I_a*r_a)-(I_l*r_se); +disp("(b) When the machine is connected as short shunt compound generator-"); +disp(sprintf("The armature current is %f A and the total emf is %f V",I_a,E_g)); + +//END diff --git a/1445/CH8/EX8.36/ch8_ex_36.sce b/1445/CH8/EX8.36/ch8_ex_36.sce new file mode 100644 index 000000000..9ed702c6f --- /dev/null +++ b/1445/CH8/EX8.36/ch8_ex_36.sce @@ -0,0 +1,37 @@ +//CHAPTER 8- DIRECT CURRENT MACHINES +//Example 36 + +disp("CHAPTER 8"); +disp("EXAMPLE 36"); + +//VARIABLE INITIALIZATION +v_t=250; //in Volts +I_l=150; //in Amperes +loss1=1200; //core loss at full load in Watts +loss2=800; //mechanical loss in Watts +r_b=0.08; //brush resistance in Ohms +r_sh=62.5; //shunt field resistance in Ohms +r_se=0.03; //series field resistance in Ohms +r_ip=0.02; //interpole resistance in Ohms + +//SOLUTION + +//solution (a) +p_o=v_t*I_l; +I_sh=v_t/r_sh; +I_a=I_l+I_sh; +r_tot=r_b+r_se+r_ip; +arm_loss=(I_a^2)*r_tot; //armature circuit copper loss +cu_loss=v_t*I_sh; //shunt field copper loss +c_loss=cu_loss+loss1+loss2; //constant loss +disp(sprintf("(a) The constant loss is %f W",c_loss)); + +//solution (b) +tot_loss=arm_loss+c_loss; //total loss +p_i=p_o+tot_loss; +eff=(p_o/p_i)*100; +disp(sprintf("(b) The full load efficiency is %f %%",eff)); + +//END + + diff --git a/1445/CH8/EX8.37/ch8_ex_37.sce b/1445/CH8/EX8.37/ch8_ex_37.sce new file mode 100644 index 000000000..3cea8b20c --- /dev/null +++ b/1445/CH8/EX8.37/ch8_ex_37.sce @@ -0,0 +1,43 @@ +//CHAPTER 8- DIRECT CURRENT MACHINES +//Example 37 + +disp("CHAPTER 8"); +disp("EXAMPLE 37"); + +//VARIABLE INITIALIZATION +p_o=50*1000; //in Watts +v_t=250; //in Volts +loss1=5000; //total core loss in Watts +loss2=2000; //total core loss in Watts (when speed is reduced to half) +speed=125/100; + +//SOLUTION + +//solution (a) + +//W_h=A*N, where W_h=hysteresis loss, A=constant and N=speed +//W_e=B*(N^2), where W_e=eddy current loss, B=constant and N=speed +//W_h+(W_e^2)=loss1 =>W_h+W_e=5000 +//(W_h/2)+(W_e/4)=loss2 =>(0.5*W_h)+(0.25*W_e)=2000 (when speed reduces to half) +//So, we get two equations +//W_h+W_e=5000.......................eq(i) +//(0.5*W_h)+(0.25*W_e)=2000..........eq(ii) +//solving the equations by matrix method +A=[1 1;0.5 0.25]; +b=[5000;2000]; +x=inv(A)*b; +W_h1=x(1,:); //to access the 1st row of 2X1 matrix +W_e1=x(2,:); //to access the 2nd row of 2X1 matrix +disp("Solution (a)"); +disp(sprintf("The hysteresis loss at full speed is %d W",W_h1)); +disp(sprintf("The eddy current loss at full speed is %d W",W_e1)); + +//solution (b) +W_h2=speed*W_h1; +W_e2=(speed^2)*W_e1; +disp("Solution (b)"); +disp(sprintf("The hysteresis loss at 125%% of the full speed is %d W",W_h2)); +disp(sprintf("The eddy current loss at 125%% of the full speed is %d W",W_e2)); + +//END + diff --git a/1445/CH8/EX8.38/ch8_ex_38.sce b/1445/CH8/EX8.38/ch8_ex_38.sce new file mode 100644 index 000000000..96d7543dc --- /dev/null +++ b/1445/CH8/EX8.38/ch8_ex_38.sce @@ -0,0 +1,30 @@ +//CHAPTER 8- DIRECT CURRENT MACHINES +//Example 38 + +disp("CHAPTER 8"); +disp("EXAMPLE 38"); + +//VARIABLE INITIALIZATION +v_t=215; //in Volts +r_a=0.4; //in Ohms +p=5*1000; //in Watts +N_g=1000; //speed as generator in rpm +ratio=1.1; //according to the solution, Φ_b:Φ_a=1.1 + +//SOLUTION + +//As generator +I_ag=p/v_t; +E_a=v_t+(I_ag*r_a); + +//As motor +I_am=p/v_t; +E_b=v_t-(I_am*r_a); +N_m=(1/ratio)*N_g*(E_b/E_a); +N_m=round(N_m); //to round off the value +disp(sprintf("The speed of the machine as motor is %d rpm",N_m)); + +//END + + + diff --git a/1445/CH8/EX8.4/ch8_ex_4.sce b/1445/CH8/EX8.4/ch8_ex_4.sce new file mode 100644 index 000000000..74fed07cb --- /dev/null +++ b/1445/CH8/EX8.4/ch8_ex_4.sce @@ -0,0 +1,34 @@ +//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 diff --git a/1445/CH8/EX8.5/ch8_ex_5.sce b/1445/CH8/EX8.5/ch8_ex_5.sce new file mode 100644 index 000000000..3cfbaaa8a --- /dev/null +++ b/1445/CH8/EX8.5/ch8_ex_5.sce @@ -0,0 +1,40 @@ +//CHAPTER 8- DIRECT CURRENT MACHINES +//Example 5 + +disp("CHAPTER 8"); +disp("EXAMPLE 5"); + +//VARIABLE INITIALIZATION +v_t=200; //in Volts +I_l=50; //in Amperes +r_a=0.1; //armature resistance in Ohms +r_f=100; //field resistance in Ohms +s_loss=500; //core and iron loss in Watts + +//SOLUTION + +//solution (a) +I_f=v_t/r_f; //I_sh is same as I_f and r_sh is same as r_f +I_a=I_f+I_l; +E_a=v_t+(I_a*r_a); +disp(sprintf("(a) The induced emf is %f V",E_a)); + +//solution (b) +arm_loss=(I_a^2)*r_a; //armature copper loss +sh_loss=(I_f^2)*r_f; //shunt field copper loss +tot_loss=arm_loss+sh_loss+s_loss; +p_o=v_t*I_l; //output power +p_i=p_o+tot_loss; //input power +bhp=p_i/735.5; //1 metric horsepower= 735.498W +disp(sprintf("(b) The Break Horse Power(B.H.P.) of the prime mover is %f H.P.(metric)",bhp)); + +//solution (c) +c_eff=(p_o/p_i)*100; +p_EE=E_a*I_a; //electrical power +m_eff=(p_EE/p_i)*100; +e_eff=(p_o/p_EE)*100; +disp(sprintf("(c) The commercial efficiency is %f %%, the mechanical efficiency is %f %% and the electrical efficiency is %f %%",c_eff,m_eff,e_eff)); + +//END + + diff --git a/1445/CH8/EX8.6/ch8_ex_6.sce b/1445/CH8/EX8.6/ch8_ex_6.sce new file mode 100644 index 000000000..31e4aebbb --- /dev/null +++ b/1445/CH8/EX8.6/ch8_ex_6.sce @@ -0,0 +1,52 @@ +//CHAPTER 8- DIRECT CURRENT MACHINES +//Example 6 + +disp("CHAPTER 8"); +disp("EXAMPLE 6"); + +//VARIABLE INITIALIZATION +p_o=20*746; //output power from H.P. to Watts (1 H.P.=745.699 or 746 W) +v_t=230; //in Volts +N=1150; //speed in rpm +P=4; //number of poles +Z=882; //number of armature conductors +r_a=0.188; //armature resistance in Ohms +I_a=73; //armature current in Amperes +I_f=1.6; //field current in Amperes + +//SOLUTION + +//solution (i) +E_b=v_t-(I_a*r_a); +w=(2*%pi*N)/60; //in radian/sec +T_e=(E_b*I_a)/w; +disp(sprintf("(i) The electromagnetic torque is %f N-m",T_e)); + +//solution (ii) +A=P; //since it is lap winding, so A=P and A=number of parallel paths +phi=(E_b*60*A)/(P*N*Z); +disp(sprintf("(ii) The flux per pole is %f Wb",phi)); + +//solution (iii) +p_rotor=E_b*I_a; //power developed on rotor +p_rot=p_rotor-p_o; //p_shaft=p_out +disp(sprintf("(iii) The rotational power is %f W",p_rot)); + +//solution (iv) +tot_loss=p_rot+((I_a^2)*r_a)+(v_t*I_f); +p_i=p_o+tot_loss; +eff=(p_o/p_i)*100; +disp(sprintf("(iv) The efficiency is %f %%",eff)); + +//solution (v) +T=p_o/w; +disp(sprintf("(v) The shaft torque is %f N-m",T)); + +//The answers are slightly different due to the precision of floating point numbers + +//END + + + + + diff --git a/1445/CH8/EX8.7/ch8_ex_7.sce b/1445/CH8/EX8.7/ch8_ex_7.sce new file mode 100644 index 000000000..510984fa8 --- /dev/null +++ b/1445/CH8/EX8.7/ch8_ex_7.sce @@ -0,0 +1,32 @@ +//CHAPTER 8- DIRECT CURRENT MACHINES +//Example 7 + +disp("CHAPTER 8"); +disp("EXAMPLE 7"); + +//VARIABLE INITIALIZATION +p_o=20*746; //output power from H.P. to Watts (1 H.P.=745.699 or 746 W) +v_t=230; //in Volts +N1=1150; //speed in rpm +P=4; //number of poles +Z=882; //number of armature conductors +r_a=0.188; //armature resistance in Ohms +I_a1=73; //armature current in Amperes +I_f=1.6; //field current in Amperes +ratio=0.8; //phi2:phi1=0.8 (here phi=flux) + +//SOLUTION + +E_b1=v_t-(I_a1*r_a); +I_a2=I_a1/ratio; //(phi2*I_a2)=(phi1*I_a1) +E_b2=v_t-(I_a2*r_a); +N2=(E_b2/E_b1)*(1/ratio)*N1; //N2:N1=(E_b2/E_b1)*(phi1/phi2) +N2=round(N2); //to round off the value of N2 (before rounding off N2=1414.695516 rpm) +disp(sprintf("The new operating speed is %d rpm",N2)); + +//The answer is slightly different due to the precision of floating point numbers + +//END + + + diff --git a/1445/CH8/EX8.8/ch8_ex_8.sce b/1445/CH8/EX8.8/ch8_ex_8.sce new file mode 100644 index 000000000..8370c62fb --- /dev/null +++ b/1445/CH8/EX8.8/ch8_ex_8.sce @@ -0,0 +1,44 @@ +//CHAPTER 8- DIRECT CURRENT MACHINES +//Example 8 + +disp("CHAPTER 8"); +disp("EXAMPLE 8"); + +//VARIABLE INITIALIZATION +v_t=250; //in Volts +r_a=0.1; //armature resistance in Ohms +r_f=125; //field resistance in Ohms +p_o=20*1000; //output power in Watts +N_g=1000; //speed as generator in rpm + +//SOLUTION + +//machine as a generator +I_l=p_o/v_t; +I_f=v_t/r_f; //I_f is same as I_sh +I_ag=I_l+I_f; +E_a=v_t+(I_ag*r_a); //induced emf = E_a = E_g + +//machine as a motor +I_l=p_o/v_t; +I_f=v_t/r_f; +I_am=I_l-I_f; +E_b=v_t-(I_am*r_a); //back emf = E_b = E_m + +//solution (a) +N_m=(N_g*E_b)/E_a; +N_m=round(N_m); //to round off the value of N_m +disp(sprintf("(a) The speed of the same machine as a motor is %d rpm",N_m)); + +//solution (b) + +//(i) +p1=(E_a*I_ag)/1000; //to express the answer in kW +disp(sprintf("(b) (i) The internal power developed as generator is %f kW",p1)); + +//(ii) +p2=(E_b*I_am)/1000; +disp(sprintf("(b) (ii) The internal power developed as motor is %f kW",p2)); + +//END + diff --git a/1445/CH8/EX8.9/ch8_ex_9.sce b/1445/CH8/EX8.9/ch8_ex_9.sce new file mode 100644 index 000000000..464608dc5 --- /dev/null +++ b/1445/CH8/EX8.9/ch8_ex_9.sce @@ -0,0 +1,29 @@ +//CHAPTER 8- DIRECT CURRENT MACHINES +//Example 9 + +disp("CHAPTER 8"); +disp("EXAMPLE 9"); + +//VARIABLE INITIALIZATION +P=4; //number of poles +v_t=230; //in Volts +I_l=52; //in Amperes +Z=600; //tottal number of conductors +r_f=115; //in Ohms +d=30/100; //airgap diameter from cm to m +l=20/100; //effective length of pole +B=4100/10000; //flux density from Gauss to Wb/m^2 + +//SOLUTION +I_f=v_t/r_f; //I_f is same as I_sh +I_a=I_l-I_f; +ar=(%pi*d*l)/P; //area of pole +phi=ar*B; //phi = flux +A=P; +T=(phi*Z*I_a)/(2*%pi*A); +disp(sprintf("The torque developed in the motor is %f N-m",T)); + +//The answer is different as 'A' has not been included in the denominator(in the book) + +//END + |