Square Vs. Round Core Legs—Balancing Core And Winding Losses
by Dennis Feucht, Innovatia Laboratories, Cayo, Belize, How2Power Today, Aug 15 2019
Focus:
When designing transformers and inductors for power electronics, engineers have a choice of
magnetic core shapes. Newer core shapes such as EC, ER, and ETD have round center legs whereas
older shapes such as EE and EI have square center legs. For toroids, both round and square or
rectangular rings prevail. This article analyzes the performance differences between round and
square shapes. Round center-posts are compared to square ones according to two criteria,
winding length—hence resistance—and thermal performance. Understanding the impact of core
center-post shapes on these two factors can help designers optimize magnetics’ performance in
the application in terms of balancing core and winding losses. This article quantifies the
differences in winding length and thermal shape factor (a measure of a core’s ability to
dissipate heat versus a sphere) for round versus square center posts.
What you’ll learn:
- How to determine whether a magnetic core with a round center leg or a square center leg will work better in your power converter design
- How to use choice of magnetic core shape to balance core and winding losses in magnetic components
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