Interlamination Insulation Design Considerations for Laminated Magnetics Operating at High Frequencies

A laminated magnetic core is comprised of alternating metallic magnetic layers and electrically insulating interlamination insulation layers, due to which eddy current losses in the core are suppressed. In practice, the nonzero conductivity of the interlamination insulation can lead to additional eddy current losses due to the electrical currents that travel across the layers. We present quantitative models which enable the determination of the necessary insulation quality of the interlamination insulation layers for various applications. For a given operating frequency range and given geometries/material properties of the magnetic material, the maximum tolerable conductivity of the interlamination material is calculated; this maximum is defined in such a way that the total eddy current losses, including the interlayer-induced losses, do not exceed the intrinsic material hysteresis losses. Understanding these maximum tolerable losses may open new design spaces for magnetic components; for example, allowing the use of interlamination insulation materials with finite conductivities may lead to a manufacturable, yet effective lamination approach for dc/dc converters based on integrated magnetics that can operate at RF switching frequencies (>3 MHz).