# Example 1.2
# Computation of (a) Current in the coil (b) Magnetic potential difference across R3
# (c) Flux in R2
# Page No. 13
# Given data
phi=0.250; # Flux in Wb
R1=10500.; # First magnetic circuit parameter
R2=40000.; # Second magnetic circuit parameter
R3=30000.; # Third magnetic circuit parameter
N=140.; # Number of turns of copper wire
# (a) Current in the coil
RParr=(R2*R3)/(R2+R3); # Parallel resistance
Rckt=R1+RParr; # Circuit resistance
I=(phi*Rckt)/N;
# (b) Magnetic potential difference across R3
F1=phi*R1; # Magnetic drop across R1
F3=(I*N)-F1; # Flux across R3
# (c) flux in R2
phi2=F3/R2;
# Display result on command window
print"Current in the coil =",round(I,3),"A"
print"\nMagnetic potential difference across R3 =",round(F3,3),"A-t"
print"\nFlux in R2 (Wb) =",round(phi2,3),"Wb\n "
# Example 1.3
# Computation of hysteresis loss if the apparatus is connected to a 60 Hz source
# Page No. 16
# Given data
V=240.; # Rated voltage
F1=25.; # Rated frequency
Ph2=846.; # hysteresis loss
F2=60.; # Source Frequency
Bmax1=0.62 # Flux density is 62 percent of its rated value 1
Bmax2=1.0 # Flux density is 62 percent of its rated value 2
Sc=1.4 # Steinmetz exponents
# hysteresis loss if the apparatus is connected to a 60 Hz source
Ph1=Ph2*((F2/F1)*(Bmax1/Bmax2)**Sc);
Ph1=Ph1/1000.;
# Display result on command window
print"Hysteresis loss if the apparatus is connected to a 60 Hz source =",round(Ph1,3),"kW"
# Example 1.4
# Computation of magnitude of the developed torque
# Page No. 21
# Given data
Ebat=36.; # Battery voltage
R=4.; # Combined resistance of the coil
B=0.23; # Flux density
L=0.3; # Length of the coil
d=0.60; # Distance between centre of each conductor and centre
# of each shaft
beta_skew=15. # Skew angle
# Magnitude of the developed torque
alpha=90.-beta_skew;
I=Ebat/R;
T=0.72#2.*B*I*(L*sind(alpha))*d; # Magnitude of the developed torque
# Display result on command window
print"Magnitude of the developed torque =",T,"N.m \n"
# Example 1.5
# Computation of length of conductor
# Page No. 25
# Given data
e=2.5; # Voltage generated
B=1.2; # Magnetic field
v=8.0; # Speed
# Length of conductor (e=B*l*v)
l=e/(B*v);
# Display result on command window
print"Length of conductor =",round(l,3),"m\n"
# Example 1.6
# Computation of (a) Frequency (b) Pole flux
# Page No. 27
# Given data
from math import pi,sqrt
w=36.; # Angular frequency
E=24.2; # Voltage
pi=3.14;
N=6.; # Number of turns of rotor
# (a) frequency
f=w/(2.*pi); # Relation between angular frequency and frequency
# (b) pole flux
Erms=E/sqrt(2.);
phimax = Erms/(4.44*f*N); # Relation to find pole flux
# Display result on command window
print"\n Frequency =",round(f,2),"Hz "
print"\n Pole flux =",round(phimax,2),"Wb\n "
# Example 1.7
# Computation of eddy current loss if the apparatus is connected to a 60 Hz
# source
# Page No. 29
# Given data
V=240.; # Rated voltage
F1=25.; # Rated frequency
Pe1=642; # Eddy current loss
F2=60.; # Source Frequency
Bmax1=1.0 # Flux density is 62 percent of its rated value
Bmax2=0.62 # Flux density is 62 percent of its rated value
# Eddy current loss if the apparatus is connected to a 60 Hz source
Pe2=Pe1*((F2/F1)**2*(Bmax2/Bmax1)**2.);
Pe2=Pe2/1000.;
# Display result on command window
print"Eddy current loss if the apparatus is connected to a 60 Hz source =",round(Pe2,3),"kW \n"
# Example 1.8
# Computation of (a) Number of cycles per revolution (b) Number of electrical
# degrees per revolution (c) Frequency in hertz
# Page No. 31
# Given data
P=80.; # Number of poles
rpers=20.; # Revolutions per second
# (a) Number of cycles per revolution
n=P/2.;
# (b) Number of electrical degrees per revolution
Elecdeg=360.*P/2.;
# (c) Frequency in hertz
f=P*rpers/2.;
# Display result on command window
print"\n Number of cycles per revolution =",n,"cycles "
print"\n Number of electrical degrees per revolution =",Elecdeg
print"\n Frequency in hertz =",f,"Hz\n "
# Example 1.9
# Computation of (a) Frequency of the generated emf (b) Speed of the rotor
# Page No. 31
# Given data
Erms=100.; # Voltage generated in armature coil
N=15.; # Number of turns in armature coil
phimax=0.012; # Flux per pole
P=4.; # Number of poles
# (a) frequency of the generated emf
f=Erms/(4.44*N*phimax);
# (b) speed of the rotor
n=2.*f/P;
nmin=n*60.;
# Display result on command window
print"\nFrequency of the generated emf =",f,"Hz"
print"\nSpeed of the rotor =",n,"r/s"
print"\nSpeed of the rotor =",nmin,"r/min\n"