Here are the slides from my presentation at the APEC magnetics industry session.
Industry session sullivan 2018.pdf
They provide an overview of the topics at the PSMA/IEEE PELS saturday magnetics workshop, focusing on dimensional effects in core loss and fringing effects.
I skipped over discussion of core loss with non-sinusoidal waveforms, because that was discussed in last year’s talk and a previous presentation providing an overview of different methods.
Our second presentation at the PSMA/IEEE PELS workshop on magnetics was on fringing, including:
Here are the Fringing Effects Presentation Slides including references at the end.
Of the three main component types needed in power converters—switches, capacitors and inductors—the most difficult to integrate on a semiconductor chip or in a planar package is the inductors. This difficulty arises partly from process compatibility challenges with magnetic materials, and is exacerbated by the fact that, because most types of electronics don’t need inductors, there has been relatively little development effort. But a more fundamental challenge is the way magnetics performance scales with size.
Capacitors and semiconductor devices can be made from thousands of small cells connected in parallel, but that approach would severely undercut the performance of magnetic components.
In this work, we examine the scaling relationships for magnetics to demonstrate the inherent difficulty of small size and low profile magnetics. Cases considered include those with winding designs limited by skin and proximity effect and those constrained by efficiency and thermal dissipation. Small-scale magnetic components are typically limited by efficiency rather than heat dissipation. With efficiency constrained, and considering high frequency winding loss effects, it is shown that power density typically scales as the linear dimension scaling factor to the fifth power.
For the full analysis, see the attached paper, Sullivan, C.R., Reese, B.A., Stein, A.L. and Kyaw, P.A.,. “On size and magnetics: Why small efficient power inductors are rare.” IEEE International Symposium on 3D Power Electronics Integration and Manufacturing (3D-PEIM), 2016.
There’s a lot we know about magnetic core loss, and at lot we don’t know. The situation is summarized in presentation slides from my presentation at the PSMA/IEEE Magnetics Workshop. The slides have the references added at the end with reference numbers sprinkled through.
People were intrigued by the three simple flux crowding simulations shown here. These aren’t intended to be highly accurate–they are based on constant permeability, and as pointed out by Bruce Carsten, the real behavior is nonlinear. But the results are still interesting and somewhat surprising. Based on loss proportional the flux density raised to the 2.5 power, the second picture–the circular hoop–doesn’t reduce loss as you might expect. Rather, it raises loss by about 3%, compared to the simple square corners at the top. But the bottom design does reduce loss, by about 8%, compared to the simple square corners.
