Chapter 1, Basic Concepts

Exa 1.1 - page 13

from __future__ import division
from numpy import sqrt
#Given data : 
R=4 #in ohm
XL=3 #in ohm
VL=400 #in volt
Vph=VL/sqrt(3) #in volt
Zph=sqrt(R**2+XL**2) #in ohm
Iph=Vph/Zph #in Ampere
#In star connected IL=Iph
IL=Iph #in Ampere
print "Line Current = %0.1f A" %IL
cosfi=R/Zph #unitless
PowerConsumed=sqrt(3)*VL*IL*cosfi #in watts
print "Total power consumed by the load = %.f Watts" %PowerConsumed 

Line Current = 46.2 A
Total power consumed by the load = 25600 Watts

Exa 1.2 - page 14

from __future__ import division
from numpy import sqrt
#Given data : 
VL=440 #in volt
IL=10 #in Ampere
#In star connected :
print "In star connected :" 
Iph=IL #in Ampere
Vph=VL/sqrt(3) #in volt
Rph=Vph/Iph #in ohm
print "Value of each resistor = %.1f ohm" %Rph
#In delta connected :
print "In delta connected :"
Iph=IL/sqrt(3) #in Ampere
Vph=Iph*Rph #in volt
print "Voltage in delta connection = %.2f volt" %Vph

In star connected :
Value of each resistor = 25.4 ohm
In delta connected :
Voltage in delta connection = 146.67 volt

Exa 1.3 - page 15

from __future__ import division
from numpy import sqrt, pi
#Given Data :
R=16 #in ohm
L=38.2 #in mH
L=38.2*10**-3 #in H
VL=400 #in volt
f=50 #in Hz
XL=2*pi*f*L #in ohm
Zph=sqrt(R**2+XL**2) #in ohm
#In star connected :
Vph=VL/sqrt(3) #in volt
Iph=Vph/Zph #in Ampere
IL=Iph #in Ampere
print "Line Current = %0.2f A" %IL
cosfi=R/Zph #unitless
print "Power factor = %.1f" %cosfi
P=sqrt(3)*VL*IL*cosfi #in watts
P/=10**3  # kW
print "Total power consumed by the load = %0.3f kW" %P

Line Current = 11.55 A
Power factor = 0.8
Total power consumed by the load = 6.400 kW

Exa 1.4 - page 15

from __future__ import division
from numpy import sqrt
#Given Data :
R=15 #in ohm
X=40 #in ohm
VL=440 #in volt
#In delta connection : 
Vph=VL #in volt
Zph=sqrt(R**2+X**2) #in ohm
Iph=Vph/Zph #in Ampere
print "Phase Current = %0.1f A" %Iph
IL=Iph*sqrt(3) #in Ampere
print "Line Current = %0.2f A" %IL

Phase Current = 10.3 A
Line Current = 17.84 A