Chapter 39: Special Machines

Example Number 39.1, Page Number:1537

In [10]:
#variable description
p=8.0 #number of poles
tp=5.0 #number of teeth for each pole
nr=50.0 #number of rotor teeth

#calculation
ns=p*tp #number of stator teeth
B=((nr-ns)*360)/(nr*ns) #stepping angle

#result
print "stepping angle is ",B,"degrees"

stepping angle is  1.8 degrees

Example Number 39.2, Page Number:1537

In [14]:
#variable declaration
B=2.5
rn=25
f=3600

#calculation
r=360/B
s=r*rn
n=(B*f)/360

#result
print "Resolution =",int(r),"steps/revolution"
print " Number of steps required for the shaft to make 25 revolutions =",int(s)
print " Shaft speed", int(n),"rps"

 Resolution = 144 steps/revolution
Number of steps required for the shaft to make 25 revolutions = 3600
Shaft speed 25 rps

Example Number 39.3, Page Number:1544

In [40]:
#variable declaration
B=15 #stepping angle
pn=3 #number of phases
nr=360/(pn*B) #number of rotor teeth

#number of stator teeth
ns1=((360*nr)/(360-(nr*B))) #ns>nr
ns2=((360*nr)/(360+(nr*B))) #nr>ns

#result
print "When ns>nr: ns= ",ns1
print "When nr>ns: ns= ",ns2

When ns>nr: ns=  12
When nr>ns: ns=  6

Example Number 39.4, Page Number:1545

In [18]:
#variable declaration
B=1.8
pn=4

#calculation
nr=360/(pn*B) #number of rotor teeth
ns=nr

#result
print "Number of rotor teeth = ",int(nr)
print "Number of statot teeth = ",int(ns)

Number of rotor teeth =  50.0
Number of statot teeth =  50.0

Example Number 39.5, Page Number:1555

In [41]:
import math

#variable declaration
er=20

#calculation
a=40
e2=er*math.cos(math.radians(a))
e1=er*math.cos(math.radians(a-120))
e3=er*math.cos(math.radians(a+120))

#result
print "a) For a=40 degrees"
print "   e2s=" ,e2,"V"
print "   e1s=" ,e1,"V"
print "   e3s=" ,e3,"V"

#calculation
a=(-40)
e2=er*math.cos(math.radians(a))
e1=er*math.cos(math.radians(a-120))
e3=er*math.cos(math.radians(a+120))

#result
print "b) For a=-40 degrees"
print "   e2s=" ,e2,"V"
print "   e1s=" ,e1,"V"
print "   e3s=" ,e3,"V"

#calculation
a=30
e12=math.sqrt(3)*er*math.cos(math.radians(a-150))
e23=math.sqrt(3)*er*math.cos(math.radians(a-30))
e31=math.sqrt(3)*er*math.cos(math.radians(a+90))

#result
print "c) For a=30 degrees"
print "   e12=" ,e12,"V"
print "   e23=" ,e23,"V"
print "   e31=" ,e31,"V"

a) For a=40 degrees
   e2s= 15.3208888624 V
   e1s= 3.47296355334 V
   e3s= -18.7938524157 V
b) For a=-40 degrees
   e2s= 15.3208888624 V
   e1s= -18.7938524157 V
   e3s= 3.47296355334 V
c) For a=30 degrees
   e12= -17.3205080757 V
   e23= 34.6410161514 V
   e31= -17.3205080757 V