Скачать или смотреть Ferrite Stress Characteristics in Common-Mode Inductor Design

Ferrite materials are very sensitive to mechanical stress, either compressive or tensile.
Under moderate stresses, the permeability of high-permeability materials is particularly affected by stress.

If it is important that the inductance be fairly stable in operation, then after the device is built, temperature cycling will help relieve these stresses and improve the stability of the core.

Also, if the number of turns is minimized, and a very thin coat of epoxy encapsulant is brushed on, it will help.

Before using, the ferrite core must be inspected for cracks. There are two problems to pay attention to when using ferrite materials:
(1) The encapsulant will causes stress.
(2) Arranging the windings directly on the magnetic core will cause stress.

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