Electric Machinery Fundamentals 5th edition

Chapter 1 (Code examples)

Example 1-2:

Import the PyLab namespace (provides set of useful commands and constants like Pi)



In [1]:

    
%pylab inline









    



Populating the interactive namespace from numpy and matplotlib

Define all the parameters:



In [2]:

    
lc = 0.4                 # Length of iron core in m
lag = 0.0005             # Length of air gaip in m
a  = 0.0012              # Area of the core in m**2
ur = 4000                # Relative permeability 
u0 = 4*pi*1e-7           # Permeability of free space in Vs/Am
n = 400                  # Number of turns on core
i = 0.6                  # Current in amps in A
fring = 1.05             # fringing factor

Calculate the iron core reluctance:



In [3]:

    
rc = lc/ (ur * u0 * a)
rc









    Out[3]:





66314.55962162306

Calculate the airgap reluctance:



In [4]:

    
rag = lag / (u0 * fring * a)
rag









    Out[4]:





315783.61724582413

Calculate the total reluctance



In [5]:

    
rtot = rc + rag
rtot









    Out[5]:





382098.1768674472

Calculate the mmf



In [6]:

    
mmf = n * i

Finally, get the flux in the core:



In [7]:

    
flux = mmf / rtot

Calculate the fluc density in the airgap



In [8]:

    
Bag = flux / (fring * a)

Display the result:



In [9]:

    
print('rc   = {} Vs/Am'.format(rc))
print('rag  = {} Vs/Am'.format(rag))
print('Flux = {} Vs'.format(flux))
print('Fluxdensity in airgap = {} Vs/m**2'.format(Bag))









    



rc   = 66314.5596216 Vs/Am
rag  = 315783.617246 Vs/Am
Flux = 0.000628110822113 Vs
Fluxdensity in airgap = 0.49850065247 Vs/m**2

(I'm using String Formatting in order to make the output above a bit nicer.)