INDUCTANCE CALCULATION
INDUCTANCE CALCULATION
(OP)
Hello,
Can anyone tell me how to calculate coil inductance?
Thank you very much!!
Kae
Can anyone tell me how to calculate coil inductance?
Thank you very much!!
Kae
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RE: INDUCTANCE CALCULATION
L = phic/I = N x phi/I = squareN x I/(Rm x I) = SquareN/Rm
where
L is coil inductance in Henries
phic is coil flux due to I in Webers
I is coil current in Amperes
N is number of coil turns
Rm is reluctance of the coil core, in 1/Henry, which has to be calculated since it varies from a coil to coil shape. It can be
Rm = Ls/(mu x muo x S)
where
Ls is path of magnetic flux inside coil in meters
mu is relative permeability of the media in per unit
muo is vacuum permeability = 4 x PI x 10 to Exp(7) in Henry/meter
S is coil crosssectional area in square meters
Dynamic approach is
Ecoil(t) = L x (di/dt) in volts
or
L = Ecoil(t) / (di/dt) in Henries
where
di/di is a derivative of current according to time t
RE: INDUCTANCE CALCULATION
di/di is supposed to be di/dt
RE: INDUCTANCE CALCULATION
is not a flux, but a "flux linkage"
RE: INDUCTANCE CALCULATION
Additional minor correction: in JBARTOS terms "phic=phi x N" is not a flux, but a "flux linkage"
///Thank you for the correction. I did not see it as the "flux." I saw it as "coil flux," which I posted, namely:
phic is coil flux due to I in Webers
In fact, the IEEE Std 100200 "Dictionary" states:
Flux Linkages. The sum of the fluxes linking the turns forming the coil, that is, in a coil having N turns, the flux linkage is:
lambda=fi1 + fi2 + .... +fiN
where
fi1 is flux linking turn 1
fi2 is flux linking turn 2
.
fiN is flux linking Nth turn.
I see that the standard is referring to the sum as flux linkages and flux linkage. I called it the coil flux.
Also, the magnetic flux:
fiA=integral over area A of (B dot product dA)
where A is area, dA is the element of A, and B is magnetic induction at the element dA. This could be applied to the coil N times to obtain coil flux or coil flux linkages.\\\
RE: INDUCTANCE CALCULATION
Nevertheless, in some particular cases, very good approaches can be got. For instance, for a single layer coil of circular turns on the free air, the inductance is approx.:
L = N^2.[R^2/(9.R+10.l)] microhenries
Where:
N: Number of turns
R: Half of diameter of coil between center of conductors (inches)
l: Length of coil (inches)
More details can be found on different manuals like "Reference data for radio engineers" Howard W. Sams & Co., Inc.
Julian
RE: INDUCTANCE CALCULATION
Arthur R. Bergen "Power Systems Analysis," PrenticeHall, Inc., Englewood Cliffs, New Jersey 07632, 1986, p. 55 indicates that
lambda=N x fi
where
lambda = flux linkages in Weber turns
fi = flux that links all the N turns of the coil
Figure 3.1 illustrates leakage fluxes in addition to the flux fi that links all the turns N. Now,
lambda= fi1 + fi2 + .. + fik + .. + fiN
where fik is the flux linking the kth turn of the coil with N turns. It appears that lambda represents flux linkages of the coil and the flux linkages form the coil flux without counting the flux leakages.