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SINGLE-ENERGY TRANSIENT OF IRONCLAD CIRCUIT. 53
approximate step-by-step method, as illustrated for the starting
transient of an alternating-current transformer in " Transient Elec- tric Phenomena and Oscillations," Section I, Chapter XII. Such methods are very cumbersome and applicable only to numerical instances.
An approximate calculation, giving an idea of the shape of the
transient of the ironclad magnetic circuit, can be made by neglect- ing the difference between the' rising and decreasing magnetic characteristic, and using the approximation of the char-
acteristic given by Frdhlich's formula: fny« '
- __^? ^ (i)
"IT ? ^WM *if
II' ^ t
which is usually represented in the form givmj|y KenrleSty:
— ?z s— 4. $£. •''"V « *?*V' (9.}
that is, the reluctivity is a linear function of tlurpielci^ttlensity.
It gives a fair approximation for higher magnetic ^<jnsitj$k
This formula is based on the fairly rational affsutyiptidtt that the
permeability of the iron is proportional to itnSumming maygnetiza-
bility. That is, the magnetic-flux density ORrt>ii8J4ts of '^Compo- nent 3Cj the field intensity, which is the flux^iiB^ in s|)4rce, and
a component <B' « (B — K} which is the fltux^clensity
carried by the iron. <B' is frequently " nj^t^ilic-flux '
density." With increasing X, <B' reaches value,
which in iron is about
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<V m 20,000 linoli pc*r cm2, *
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\ f/;f}
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t ' i'. ^ ,; ' %
At any density <B', the remaining magnetkability 'then is
<B00/—(&'7 and, assuming the (metallic) permeability as proportional
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hereto, gives
and. substituting |
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<$>'
M=^7
gives
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* See "On the Law of Hysteresis/' Part II, AXE.E. Transactions, 1892,
page 621. ' •
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