how to select the suitable high-power inductor magnetic core in switch mode power supply design

Is magnetic powder core or iron powder core better? I believe it is a common question that many engineers encounter when designing switch mode power supply solutions. The selection and comparison of magnetic cores, powder cores, iron silicon aluminum, and ferrite are frequently discussed by engineers in the selection of magnetic cores for high-power inductors. There are quite a few choices of magnetic cores for high-power inductors in the market, including iron silicon aluminum (Kool M?), iron powder core, iron silicon (silicon steel lamination), gap ferrite, molybdenum pomo (MPP), and high flux. So what are their characteristics suitable for what kind of application?
Comparison of magnetic core materials

Iron silicon aluminum and interstitial ferrite

Iron silicon aluminum and interstitial ferrite are two commonly used materials. In terms of soft saturation, interstitial ferrite must be designed in the safe zone of the descent curve. Iron silicon aluminum (Kool M?) is designed within a controlled descent curve range, which can provide good fault tolerance characteristics, especially at high power.

In terms of magnetic flux comparison, assuming a specific 50% decrease in design point, the magnetic flux of Kool M? Is more than twice that of gap ferrite, which can reduce the size of the magnetic core by 35%. During design, the size of the magnetic core can be reduced by 30% to 35%.

The soft saturation curve endows the Kool M? Design with fault tolerance, while interstitial ferrite does not.

The magnetic ability of ferrite varies with temperature, while iron silicon aluminum (Kool M?) remains relatively stable. Many ferrite suppliers or manufacturers will provide information on the material differences of their products in different environments ranging from 25 ℃ to 100 ℃. Due to the different materials, structures, and interstitial ferrite of iron silicon aluminum, the changes will not be significant with temperature.

In terms of edge loss, Kool M? Does not experience edge loss, while interstitial ferrite has significant edge loss. The gap part of the iron core will experience increased losses as the temperature increases. Iron silicon aluminum (Kool M?) also has gaps, but this is a uniform distributed gap because this form is better for high-power applications.

For size and energy storage, it can be seen from the comparison of LI2 values between iron silicon aluminum (Kool M?) and manganese zinc ferrite that when the size is both 55mm, 60? Is used for testing iron silicon aluminum?, Iron silicon aluminum (Kool M?) has an energy storage capacity of about twice that of manganese zinc ferrite in terms of volume size, as shown in Table 1.

When the energy storage is the same and the LI2 value is the same, the volume of iron silicon aluminum (Kool M?) is greatly reduced, which effectively reduces the design size for designers. As shown in Table 2.

Gap ferrite also has many advantages, can it have a high effective magnetic permeability? Eff, ferrite can be above 500, while iron silicon aluminum (Kool M?) is currently limited by? Eff=125. Gap ferrite is more suitable for some low-power designs