CHAPTER01 : MAGNETICS ELECTROMAGNETIC FORCES GENERATED VOLTAGE AND ENERGY CONVERSION

Example E02 : Pg 13

In [1]:
#  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 "
Current in the coil  = 49.362 A

Magnetic potential difference across R3 = 4285.714 A-t

Flux in R2 (Wb) = 0.107 Wb
 

Example E03 : Pg 16

In [2]:
#  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"
Hysteresis loss if the apparatus is connected to a 60 Hz source = 1.04 kW

Example E04 : Pg 21

In [3]:
#  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"
Magnitude of the developed torque = 0.72 N.m 

Example E05 : Pg 25

In [4]:
#  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"
Length of conductor  = 0.26 m

Example E06 : Pg 27

In [5]:
#  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 "
 Frequency = 5.73 Hz 

 Pole flux = 0.11 Wb
 

Example E07 : Pg 29

In [6]:
#  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"
Eddy current loss if the apparatus is connected to a 60 Hz source  = 1.421 kW 

Example E08 : Pg 31

In [7]:
#  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 "
 Number of cycles per revolution = 40.0 cycles 

 Number of electrical degrees per revolution = 14400.0

 Frequency in hertz = 800.0 Hz
 

Example E09 : Pg 31

In [8]:
#  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"
Frequency of the generated emf = 125.125125125 Hz

Speed of the rotor = 62.5625625626 r/s

Speed of the rotor = 3753.75375375 r/min