Eddy-Current Effects In Magnetic Design (Part 6): Winding Bundles
by Dennis Feucht, Innovatia Laboratories, Cayo, Belize, How2Power Today, Mar 17 2017
Focus:
This article series closes with an additional design consideration when multistrand windings or
bundles are used to reduce winding resistance because of eddy-current effects. Strands have an
equivalent number of layers within a bundle and the layer value for use in the Dowell formula
(and graphs) of the previous part 5 can be approximated from the number of strands with the
same current polarity. This part derives the formula for that approximation, which allows
calculation of the layer value, M, from parameters such as number of strands, strands per
layer, and strand packing factor. Then, this part delves into eddy current effects encountered
in the special case of unibundle construction where primary and secondary strands are all
twisted in the same bundle. In this unibundle situation, we have to consider two possibilities—
one is the simple case where strand placement within the bundle is controlled such that strands
with opposing currents are distributed uniformly within the bundle. The other is the more
complex case where these strands are randomly distributed.
What you’ll learn:
- How to apply Dowell’s formula to inductors and transformers wound using unibundle construction (i.e. where primary and secondary wire strands are twisted together)
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