Magnetics Optimization (Part 2): Maximum Power Transfer Of The Primary-Referred Circuit

Focus:

This two-part article reexamines loss optimization in the design of transductors (i.e. transformers and coupled inductors) demonstrating that equalizing winding and core losses does not result in maximum power transfer through a transductor. While part 1 derived refined criteria for power-transfer optimization from a secondary-referred circuit model, here in part 2, max-η conditions will be derived for a circuit model referred to the primary side of the transductor. The primary-referred circuit model differs from the secondary-referred circuit model, as do the associated max power transfer functions. The revelation that these transfer functions are not the same provides proof that the usual approach to winding-referred modeling of transductors is inaccurate. While the primary-referred circuit model continues down the path of optimizing efficiency, η, an alternative possibility is the use of maximum output power as the optimization criterion. But this has undesirable consequences. This part 2 discussion also considers the possible effect of a current source load on the maximum power transfer, leading to the conclusion that both primary and secondary winding resistance must be retained in transductor models used to optimize power transfer. Finally, a heuristic formula for the power-loss ratio for overall maximum power transfer is derived.

What you’ll learn:

• How to optimize power transfer in transformer and coupled inductor designs
• How to understand why equalizing core and winding losses does not maximize power transfer in magnetic components

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Author & Publication:

Dennis Feucht, Innovatia Laboratories, Cayo, Belize, How2Power Today, Sep 16 2015

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