Eddy-Current Effects In Magnetic Design (Part 6): Winding Bundles

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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Author & Publication:

Dennis Feucht, Innovatia Laboratories, Cayo, Belize, How2Power Today, Mar 17 2017

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