# CHAPTER 5: ARMATURE REACTION AND COMMUTATION IN DYNAMOS¶

## Example 5.1, Page number 140¶

In [1]:
#Variable declaration
conductors = 800.0   #Number of conductors
I_a = 1000.0         #Rated armature current(A)
P = 10.0             #Number of poles
pitch = 0.7          #Pole-face covers 70% of the pitch
a = P                #Number of parallel paths for Simplex lap-wound

#Calculation
Z = conductors/P     #Number of armature conductors/path under each pole
Z_a = Z*pitch        #Active armature conductors/pole
Z_p = Z_a/a          #Number of pole face conductors/pole

#Result
print('Number of pole face conductors/pole , Z_p = %.1f or %.f conductors/pole' %(Z_p,Z_p))

Number of pole face conductors/pole , Z_p = 5.6 or 6 conductors/pole


## Example 5.2, Page number 140¶

In [1]:
#Variable declaration
conductors = 800.0    #Number of conductors
I_a = 1000.0          #Rated armature current(A)
I_l = I_a             #Load or total current entering the armature(A)
P = 10.0              #Number of poles
pitch = 0.7           #Pole-face covers 70% of the pitch
a = P                 #Number of parallel paths for Simplex lap-wound
alpha = 5.0           #Number of electrical degress that the brushes are shifted

#Calculation
Z = conductors/P                                      #Number of armature conductors/path under each pole
A_Z_per_pole = (Z*I_l)/(P*a)                          #Cross magnetizing ampere-conductors/pole
At_per_pole = (1.0/2)*(8000/1)                        #Ampere-turns/pole
frac_demag_At_per_pole  = (2*alpha)/180*(At_per_pole) #Fraction of demagnetizing ampere-turns/pole
beta = 180-2*alpha                                    #Cross-magnetizing electrical degrees
cross_mag_At_per_pole = (beta/180)*(At_per_pole)      #Cross-magnetizing ampere-turns/pole

#Result
print('(a) The cross-magnetizing ampere-conductors/pole = %.1f ampere-conductors/pole' %A_Z_per_pole)
print('    The cross-magnetizing ampere-turns/pole = %.1f At/pole' %At_per_pole)
print('(b) The fraction of demagnetizing ampere-turns/pole = %.1f At/pole' %frac_demag_At_per_pole)
print('(c) The cross-magnetizing ampere-turns/pole = %.f At/pole' %cross_mag_At_per_pole)

(a) The cross-magnetizing ampere-conductors/pole = 800.0 ampere-conductors/pole
The cross-magnetizing ampere-turns/pole = 4000.0 At/pole
(b) The fraction of demagnetizing ampere-turns/pole = 222.2 At/pole
(c) The cross-magnetizing ampere-turns/pole = 3778 At/pole