News

Description of the calculation formula of the hollow coil inductance

Features and uses of air-core coils: simple structure, high precision of inductance, small distributed capacitance, high self-resonance frequency, small temperature coefficient, stable
It has good properties and strong anti-interference ability. It is an inductor that can be applied at high frequencies.
Air-core coils can usually be used as current transformers, with frequency bandwidth, small size, light weight, easy for digital measurement, and microcomputer
protection. A wide range of applications for television technology, audio technology, communication transmission, reception and power supply filtering, VCD radio heads, antenna amplifiers,
Recording machines, antenna microphones and other fields.
The main products of Fuying Electronics include:
1) Acoustic products (hearing aid coils, hearing aid inductors)
2) Consumer electronics (inductor coils, electronic coils, air-core coils, computer hard disk coils, self-adhesive coils, skeleton/Bobbin coils, magnetic rod coils, solar toy coils,
Coin coils, etc.
3) Auto parts (ABS sensor, multimedia antenna coil, car alarm coil, car igniter coil, etc.)
4) ID, RFID (ISO card ~ contact and non-contact, sensor coil, animal tracker coil, army identification coil, subway IC coil,
Electronic locks, induction coils, etc.
5) Electronic PCB plug-in assembly, various electronic parts assembly
6) Trade items (connection lines, connecting cables, hardware, metal parts, color printing parts, electronic toys, electronic small machines, etc.)

The calculation formula of the air-core coil is as follows:

Load its inductance 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 (operating 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

Air core coil 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: Wei Heng
Coil diameter D unit: cm
Number of turns in the coil 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= Coil turns (circle)
AL= inductance
H-DC=DC magnetizing force I= Passing current (A)
l= magnetic circuit length (cm)
l and AL value size, refer to the Microl 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 look-up)
You can see the degree of decrease in L value (μi%)

2. Introduce an empirical formula
L=(k*μ0*μs*N2*S)/l
among them
00 is vacuum permeability = 4π * 10 (-7). (10 minus seven powers)
Ss is the relative magnetic permeability of the inner core of the coil, and μs=1 for the air-core coil
N2 is the square of the number of turns of the coil
S Coil cross-sectional area 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

PREVIOUS：The difference between magnetic ring and induNEXT：Definition of electromagnetic coil enameled w