Modeling Magnetic Core Offers Insight into Behavior, Operating Range, Saturation

Focus:

For designers to understand the behavior of chokes and inductors used for energy storage and release, they need to model how the magnetic core in these components will behave, especially how the core will saturate. This first half of this article derives key equations for modeling core saturation. It starts by deriving an equation for generating the classical B-H curve and then derives an expression for inductance as a function of magnetizing current, which ultimately is what’s needed to determine the current at which the core saturates. A simple rearrangement of the last expression yields magnetizing current as a function of inductance, which will be used directly to determine the saturation current. The second half of this article gives examples of how these derived equations can be applied, plugging in actual values to plot a B-H curve, a graph of inductance versus magnetic field strength, and a graph of inductance versus magnetizing current. The article calculates permeability as the slope of a B- H curve; and determines the saturation current from a graph of inductance vs. magnetizing current.

What you’ll learn:

• How to model the saturation of an inductor or choke
• How to generate a classic B-H curve and plots of Inductance vs magnetic field strength and inductance vs magnetizing current for an inductor or choke
• How to determine core permeability from a B-H curve

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Author & Publication:

Gregory Mirsky, Electronic Design, Sep 09 2016

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