Area-Product Method Can Simplify Core Selection—But Beware Of The "Constants"
by Dennis Feucht, Innovatia Laboratories, Cayo, Belize, How2Power Today, Aug 17 2015
Focus:
A popular method for simplifying core selection for a given transductor (transformer or coupled
inductor) power level is the area-product method. This article reveals the assumptions of the
method. The area-product method of core sizing is based on the winding-window turns maximum
constraint, NW = AW/(Ac/kp) = AW/Acwp, where Aw is the winding window area; kp < 1, and is the
wire packing factor and Ac is the conductive area of the wire. Then Acwp is the larger area
occupied by a single turn, taking the packing factor into account. The area-product method
chooses core size from the equation, area product = A·Aw, where A is the magnetic-path cross-
sectional area of the core. In applying the above equation, it is typically assumed that
certain terms such as kp are constant. However, these terms are actually dependent on variables
such as wire size and other parameters. These relationships are explained here.
What you’ll learn:
- How to apply the area-product method of core selection for transformers or coupled inductors
- How to understand the variability of the “constants†in the area-product method of core selection
- How to understand the variation in wire packing factors as a function of wires size
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