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Introduction to the working principle of the inductor

1. The working principle of the inductor _ the hindrance of the inductor to the alternating current
Why is the inductance hindering AC power? When the AC power passes through the inductor coil, the current is changing at all times, and the self-induced electromotive force is inevitably generated in the inductor coil, which hinders the change of the current, thus forming a hindrance to the current.
2. Inductive filtering principle
From the expression I=U/(XL) of the Ohm's law in the purely inductive circuit and the inductive reactance formula XL=2πfL of the coil, the inductive reactance is related to the frequency of the passing current. The larger the inductance L, the higher the frequency f, the larger the inductive reactance and the smaller the current. Therefore, the inductor has the characteristics of “through DC, resisting AC” or “passing low frequency and blocking high frequency” in the circuit. So the inductor has a filtering effect
3. Expression of Ohm's law in purely inductive circuits
In a purely inductive circuit, the current intensity is proportional to the voltage: I = U / (XL) This is the expression of Ohm's law in a purely inductive circuit. Comparing this expression with I=U/R, it can be seen that XL is equivalent to the resistance R.XL indicates the magnitude of the inductance hindering the alternating current, called inductive reactance, and its unit is also ohm.
4. Inductive reactance formula of the coil
The relationship between the inductive reactance XL of the coil and the self-inductance coefficient L and the frequency f of the alternating current is: XL = 2 лfL.
Inductance calculation formula [common] Calculation formula of various inductors

Inductance is calculated as follows: coil formula
Impedance (ohm) = 2 * 3.14159 * F (operating frequency) * Inductance (mH), setting requires 360 ohm impedance, therefore: inductance (mH) = impedance (ohm) ÷ (2*3.14159) ÷ F (working Frequency) = 360 ÷ (2*3.14159) ÷ 7.06 = 8.116mH According to this, the number of windings can be calculated:
Number of turns = [inductance * { ( 18 * circle diameter (吋)) + ( 40 * circle length (吋))}] ÷ circle diameter (吋) number of turns = [8.116 * {(18*2.047) + (40 *3.74)}] ÷ 2.047 = 19 laps

Hollow inductance calculation formula
Hollow inductance calculation formula: L(mH)=(0.08D.D.N.N)/(3D+9W+10H)
D------coil diameter
N------ coil turns
D-----wire diameter
H----coil height
W----coil width
The units are mm and mH respectively. .

Air core inductance calculation formula:
l=(0.01*D*N*N)/(L/D+0.44)
Coil inductance l Unit: Micro-Heng Coil diameter D unit: cm Coil number N unit: 匝 Coil length L unit: cm

Frequency inductance capacitance calculation formula:
l=25330.3/[(f0*f0)*c]
Working frequency: f0 Unit: MHZ This question f0=125KHZ=0.125
Resonant capacitor: c Unit: PF This question is defined as c=500...1000pf, which can be determined by itself or by Q value.
Resonant inductance: l Unit: Weiheng

Calculation formula of coil inductance
1. For the circular CORE, the following formula is available: (IRON)
L=N2. AL L= inductance value (H)
H-DC=0.4πNI / l N= Number of turns of the coil (circle) AL= inductance
H-DC=DC magnetizing force I= Passing current (A) l= Magnetic path length (cm)
l and the value of AL, refer to the Micrometal comparison table. For example: Take T50-52 material, the coil is 5 turns and half, and its L value is T50-52 (indicating OD is 0.5 inch). After checking the table, its AL value is about 33nH.
L=33. (5.5) 2 = 998.25nH ≒ 1μH
When 10A current flows, its L value can be changed by l=3.74 (check the table)
H-DC=0.4πNI / l = 0.4×3.14×5.5×10 / 3.74 = 18.47 (after looking up the table) to understand the degree of decrease in L value (μi%)
2. Introduce an empirical formula L=(k*μ0*μs*N2*S)/l where
00 is vacuum permeability = 4π * 10 (-7). (10 is negative to the seventh power) μs is the relative magnetic permeability of the inner core of the coil, and μs=1 N2 for the air-core coil is the square of the number of turns of the coil
The cross-sectional area of the S coil, in square meters l The length of the coil, in meters

The k factor depends on the ratio of the radius (R) of the coil to the length (l).
The unit of calculated inductance is Henry.
k value table
2R/l k 0.1 0.96 0.2 0.92 0.3 0.88 0.4 0.85 0.6 0.79 0.8 0.74 1.0 0.69 1.5 0.6 2.0 0.52 3.0 0.43 4.0 0.37 5.0 0.32 10 0.2 20 0.12

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