Design of Iron Powder Core Filter Inductor 3

Selection of Three Magnetic Core Materials

When making filter inductors and selecting the appropriate magnetic core material, in addition to preventing magnetic core saturation, the constant magnetic permeability of the magnetic core must also be considered. It should be pointed out that some designers often only pay attention to the indicators of inductance and choose materials with high magnetic permeability to reduce the number of turns in the coil. However, when the rated current of the inductor is large, whether the inductance decreases, to what extent it decreases, and whether it will reach saturation, should be considered relatively small. This should be avoided with caution.diode

Table 1 compares the constant magnetic permeability characteristics of some magnetic core materials for reference when selecting. The constant magnetic permeability range mentioned in the table refers to the magnetic permeability that will not be lower than 50% within this DC magnetization force range. Reduce the DC magnetization force and correspondingly increase the percentage of magnetic permeability. Table 2 shows the percentage of magnetic permeability of iron powder cores with a magnetic permeability of 75 at different DC magnetization forces. 4. Calculation Formulas

Table 3 Characteristic Parameters of Iron Powder Core (Material 26)

AL（nH/N2）So(mm2)

In order to better design inductors and meet the requirements of constant magnetism, it is necessary to master some magnetic formulas proficiently and understand some necessary magnetic knowledge.diode

The DC magnetization force mentioned above can be calculated through (1):

H=0.4πNI/lOe(1)

Or H=NI/LA/cm (1 ′)

Here N is the number of coil turns; I is the current, measured in amperes (A); L is the average magnetic circuit length of the magnetic core, measured in centimeters (cm). By transforming the above formula as follows:diode