Core Design Manual
HANNA CURVE CALCULATIONS
FIGURE 22 - SUPERPERM 49 .004" THICKNESS
- 60/400 HZ
Required L = 10 henry in an MBH-18 cut core Superperm 49 4 mil with I = .1
amperes dc. As calculated V = 71.02 cm3 and l = 17.62 cm.
Calculate LI2/V = 14.08 x 10-4. For estimated B = 1000g.,
NI/l = 16, and a/l is approximately .00200. Substituting for I and l, N =
2837 turns. The total air gap is approximately .002 x 17.62 = .035 cm or
A spacer .007 inch thick will establish this total
B = Incremental Induction in Gausses.
I = d.c. Current in Amperes.
L = a.c. Inductance in Henries.
V = Core Volume in Cubic Centimeters.
a = Total Air Gap length in Centimeters.
l = Magnetic Path length in Centimeters.
FIGURE 23 - SUPERPERM 80 .004" THICKNESS - 60/400 HZ
HANNA CURVES* provide a simplified method of calculating inductances with direct
current, and for determining the optimum air gap. Where L is the a.c. inductance
in henries, I is the d.c. current in amperes, and V is the core volume in cubic
centimeters; calculate LI² /V and enter the left side of the chart at that ordinate.
Extend to the right along this ordinate to the appropriate B, for a.c. induction
in gausses, and select the indicated abcissa for NI/. Calculate required turns
by substituting the centimeters of path length in the core material for , and
for the d.c. amperes, I. The optimum ratio of air gap length to path length
(a/) applies to the points
* "Design of Reactors and Transformers Which Carry Direct Current", C.R.
Hanna, Journal AIEE, Vol. 46, February 1927.