initial commit / add all books

1 files changed, 34 insertions, 0 deletions

diff --git a/1938/CH3/EX3.17/3_17.sce b/1938/CH3/EX3.17/3_17.sce
new file mode 100755
index 000000000..a0d8a2a84
--- /dev/null
+++ b/1938/CH3/EX3.17/3_17.sce
@@ -0,0 +1,34 @@
+clc,clear

+printf('Example 3.17\n\n')

+

+V=500

+R_a=0.22,R_sh= 250//armature resistance and shunt field resistance

+I=5 //no load current

+motor_input_NL=V*I   //no load motor input

+I_sh=V/R_sh

+I_a_NL= I- I_sh //no load armature current

+arm_cu_loss_NL = R_a*I_a_NL^2 //no load armature copper loss

+constant_loss = motor_input_NL - arm_cu_loss_NL 

+

+//When motor draws 100 A current 

+I=100

+I_a = I - I_sh

+arm_cu_loss  =R_a* I_a^2  //armature copper loss

+total_losses =   arm_cu_loss +  constant_loss

+motor_input = V*I

+motor_output = motor_input -total_losses 

+eta_m=100*(motor_output/motor_input) //motor efficiency

+printf('(i)Efficiency of motor at 100 A current is %.2f percent \n',eta_m)

+

+//part(b)

+E_b_NL= V- I_a_NL*R_a //back emf at no load

+E_b= V- I_a*R_a //back emf at 100 A 

+//E_b is proportional to N.. and using componendo dividendo

+speed_change= 100*((E_b_NL - E_b)/E_b)

+printf('(ii)Percentage change in speed = %.3f percent\n\n',speed_change)

+

+

+printf('Note that the following were assumptions made\n')

+printf('(i) Due to heating , resistance of shunt field winding will be increased which will reduce the shunt field current.This will decrease the flux which is neglected\n')

+printf('(ii) Though the motor speed is changing from no load to given load , the mechanical losses are assumed to be cosnstant\n')

+printf('(iii)The effect of armature reaction aon main pole flux and its effect on iron loss is neglected')