CHAPTER 11: SPECIALIZED DYNAMOS

Example 11.1, Page number 372

In [1]:
#Variable declaration
#Given Torque-Speed relations shown in Fig.11-3b page no-371 for a dc servomotor

#Calculation
#Case(a)
S = 800.0            #Motor speed at point x(rpm). Extrapolating to load line point x
V = 60.0             #Armature voltage at point x(V)
#Case(b)
T = 4.5              #At standstill, 60 V yields 4.5 lb-ft of starting torque
#Case(c)
P_c = T*S/5252       #Power delivered to the load(hp). From case(a)
P_c_watt = P_c*746   #Power delivered to the load(W)
#Case(d)
T_d = 1.1            #Torque for continuous duty without cooling fan(lb-ft). At point o
S_d = 410.0          #Maximum load speed(rpm)
#Case(e)
T_e = 2.4            #Torque for continuous duty with cooling fan(lb-ft). At point w
S_e = 900.0          #Maximum load speed(rpm)
#Case(f)
P_d = T_d*S_d/5252   #Power delivered to the load(hp). From case(d)
P_d_watt = P_d*746   #Power delivered to the load(W)
#Case(g)
P_e = T_e*S_e/5252   #Power delivered to the load(hp). From case(e)
P_e_watt = P_e*746   #Power delivered to the load(W)
#Case(h)
A = 65.0             #Upper limit of power range A(W)
B = 305.0            #Upper limit of power range B(W)

#Result
print('Case(a): Motor speed when load torque is 2.1 lb-ft at point x , S = %.f rpm' %S)
print('         Armature voltage when load torque is 2.1 lb-ft at point x , V = %.f V' %V)
print('Case(b): Motor starting torque using the voltage found in part(a) , T_st = %.1f lb-ft' %T)
print('Case(c): Power delivered to the load under conditions given in part(a) , P = %.3f hp = %.f W' %(P_c,P_c_watt))
print('Case(d): Maximum load speed for continuous duty without cooling fan , S = %.f rpm' %S_d)
print('         Torque for continuous duty without cooling fan , T = %.1f lb-ft' %T_d)
print('Case(e): Maximum load speed for continuous duty with cooling fan , S = %.f rpm' %S_e)
print('         Torque for continuous duty with cooling fan , T = %.1f lb-ft' %T_e)
print('Case(f): Power delivered to load in part(d) , P = %.4f hp = %.1f W' %(P_d,P_d_watt))
print('Case(g): Power delivered to load in part(e) , P = %.3f hp = %.f W' %(P_e,P_e_watt))
print('Case(h): Upper limit of power range , A = %.f W' %A)
print('         Upper limit of power range , B = %.f W' %B)

Case(a): Motor speed when load torque is 2.1 lb-ft at point x , S = 800 rpm
         Armature voltage when load torque is 2.1 lb-ft at point x , V = 60 V
Case(b): Motor starting torque using the voltage found in part(a) , T_st = 4.5 lb-ft
Case(c): Power delivered to the load under conditions given in part(a) , P = 0.685 hp = 511 W
Case(d): Maximum load speed for continuous duty without cooling fan , S = 410 rpm
         Torque for continuous duty without cooling fan , T = 1.1 lb-ft
Case(e): Maximum load speed for continuous duty with cooling fan , S = 900 rpm
         Torque for continuous duty with cooling fan , T = 2.4 lb-ft
Case(f): Power delivered to load in part(d) , P = 0.0859 hp = 64.1 W
Case(g): Power delivered to load in part(e) , P = 0.411 hp = 307 W
Case(h): Upper limit of power range , A = 65 W
         Upper limit of power range , B = 305 W

Example 11.2, Page number 379

In [1]:
#Variable declaration
n = 3.0       #Number of stacks or phases
P_a = 16.0    #Number of rotor teeth
P_b = 24.0    #Number of rotor poles

#Calculation
alpha_a = 360/(n*P_a)     #Stepping angle(degree/step) 
alpha_b = 360/(n*P_b)     #Stepping angle(degree/step)

#Result
print('Case(a): Stepping angle , α = %.1f°/step' %alpha_a)
print('Case(b): Stepping angle , α = %.1f°/step' %alpha_b)

Case(a): Stepping angle , α = 7.5°/step
Case(b): Stepping angle , α = 5.0°/step

Example 11.3, Page number 381

In [1]:
#Variable declaration
P = 50.0     #Number of rotor teeth

#Calculation
alpha = 90/P #Stepping length(degrees)

#Result
print('α = %.1f° ' %alpha)

α = 1.8°

Example 11.4, Page number 388

In [1]:
#Variable declaration
tou = 0.1   #Pole pitch of a double-sided primary LIM(m)
f = 60.0    #Frequency applied to the primary LIM(Hz)

#Calculation
v_s = 2*f*tou   #Synchronous velocity(m/s)

#Result
print('Synchronous velocity , v_s = %.f m/s' %v_s)

Synchronous velocity , v_s = 12 m/s

Example 11.5, Page number 388

In [1]:
#Variable declaration
v_s = 12.0   #Synchronous velocity(m/s)
v = 10.0     #Linear velocity of secondary sheet(m/s)

#Calculation
s = (v_s-v)/v_s   #Slip of the DSLIM

#Result
print('Slip of the DSLIM , s = %.3f' %s)

Slip of the DSLIM , s = 0.167