from math import sqrt
horsepower=2.5 # rating of induction motor in horsepower at half load
Vl=230. # terminal voltage of motor in volts
Il=7. # load current of motor in amperes
pf=0.8 # power factor of the machine
Pin=sqrt(3.)*Vl*Il*pf # input power in watts
print"Pin=",Pin,"W"# The answer may vary due to roundoff error
Whp=746. # watts per hp
Pout=horsepower*Whp # output power in watts
print"Pout=",Pout,"W"
print"n=",Pout/Pin# The answer may vary due to roundoff error # efficiency of the machine
print"Losses=Pin-Pout=",Pin-Pout,"W"# The answer may vary due to roundoff error # losses in the machine in watts
# the below exmaple is an extension of Ex1_1.sce
from math import sqrt
Vl=230. # terminal voltage of machine in volts
Il=7. # current drawn by machine in amperes
pf=0.8 # power factor of machine
Pin=sqrt(3.)*Vl*Il*pf # from Ex1_1 # input power in watts
Losses=365. # in watts
Pout=Pin-Losses # output power in watts
Whp=746. # watts per hp
print"n=1-(Losses/Input)=",1.-(Losses/Pin) # The answer may vary due to roundoff error # efficiency of the machine
print"Pout=",Pout,"W"# The answer may vary due to roundoff error
print"Pout=",Pout/Whp,"hp"# The asnwer may vary due to roundoff error # output power in horsepower
from math import sqrt,pi
f=60. # frequency of voltage source in Hz
x=1.9 # Steinmetz coefficient
V=80. # applied sinusoidal voltage in volts
t=100. # no of turns wound on a coil
hc=500. # hysteresis coefficient
w=2.*pi*f # angular frequency in rads/sec
phimax=(sqrt(2.)*V)/(t*w)# maximum value of flux in the core in webers
print"phimax=",phimax,"Wb"# the answer may vary due to roundoff error
A1=0.0025 # cross-sectional area of core in metre square
Bmax1=phimax/A1 # flux density in core A in tesla
print"Bmax=",Bmax1,"T"# the answer may vary due to roundoff error
lfe1=0.5 # mean flux path length of core A in meters
VolA=A1*lfe1 # volume of core A in metre cube
print"VolA=",VolA,"metre cube"
# for core A
Ph1=VolA*f*hc*(Bmax1**x) # hysteresis loss in core A in watts
print"Ph=",Ph1,"W"# the answer may vary due to roundoff error
# for core B
A2=A1*3. # cross sectional area of core B in metre square
lfe2=0.866 # mean flux path length of core B in metres
Bmax2=phimax/A2 # flux density in core B in tesla
VolB=A2*lfe2 # volume of core B in metre cubes
Ph2=VolB*f*hc*(Bmax2**x) # hysteresis loss of core B in watts
print"Ph=",Ph2,"W"# the answer may vary due to roundoff error
V1=240. # voltage applied to a winding of transformer(three phase) in volts
f1=60. # initial applied frequency in Hz
f2=30. # reduced frequency in Hz
Phe1=400. # core loss in watts at f1 frequency
Phe2=169. # core losses in watts at f2 frequency
print"V2=",(f2*V1)/f1,"V"# voltage at 30 Hz frequency
print"Ph+e/f=Ch+Ce*f"# equation for claculating hysteresis and eddy current loss coefficients
#a=[1 f1;1 f2] # left hand side matix for the equation above
#b=[Phe1/f1;Phe2/f2] # right hand side matrix for the equation above
#c=inv(a)*b
Ch=4.6#c(1,:)# hysteresis loss coefficient in W/Hz
Ce=0.0344#c(2,:)# eddy current loss coefficient in W/(Hz*Hz)
print"Ph=",Ch*f1,"W"# ans may vary due to roundoff error # hysteresis loss in watts at 60 Hz
print"Pe=",round(Ce*f1*f1),"W"# ans may vary due to roundoff error # eddy current loss at 60 Hz in watts
from math import sqrt
Pk=75. # core loss of transfomer in watts
R=0.048 # internal resistance in ohms
V2=240.# secondary voltage in volts
I2=sqrt(Pk/R)# secondary current in amperes
print"I2=",round(I2),"A"# ans may vary due to roundoff error
print"|S|=V2*I2=",round(V2*I2),"VA"# The answer in the textbook is wrong # output volt ampere of transformer
sfl=1746 # speed at full load in rev/min
snl=1799.5 # speed at no load in rev/min
print"Voltage Regulation=",round((snl-sfl)/sfl,5) # the ans may vary due to round of error
Vnl=27.3 # no load voltage in volts
Vfl1=24. # full load voltage at power factor 1 in volts
print"(Vnl-Vfl/Vfl)=",(Vnl-Vfl1)/Vfl1# ans may vary due to roundoff error
Vfl2=22.1 # full load voltage at power factor 0.7 in volts
print"Voltage Regulation=",round((Vnl-Vfl2)/Vfl1,4)