by Dennis Feucht, Innovatia Laboratories, Cayo, Belize, How2Power Today, Sep 14 2018
Focus:
In previous articles on interwinding power transfer in transformers and coupled
inductors, design formulas were derived for maximum power transfer having peak winding
transfer efficiency, ηmax, using the transfer voltage ratio, υp and the ratio of
winding to effective core resistance, βp. In this article, some extended development
of power-transfer theory applies the additional constraint of holding the secondary
current (i.e. the load current) constant as βp is varied. The migration of the
operating-point (op-pt) at ηmax on one efficiency curve to another η curve at a
different βp under constant output current shows that as winding resistance is varied
in design, the η op-pt can move to either side of the new ηmax. As current is varied,
the op-pt on a given η curve also moves and efficiency changes, sometimes
dramatically. This article analyzes and derives the theoretical optimal peak
efficiency for a power converter when its load spans a range and uses that information
to design the transformer.
What you’ll learn:
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