Inductor Coil

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Inductor Coil
An inductor coil is a coil of wire wound around an insulating tube. The wires are insulated from each other, and the insulating tube can be hollow or contain an iron core or a magnetic powder core, referred to as an inductor. It is represented by L, and the units are Henry (H), millihenry (mH), and microhenry (uH). 1H=10^3mH=10^6uH.
1. Classification of Inductors
Classification by inductance form: fixed inductance, variable inductance.
Classification by magnetic conductor properties: air-core coil, ferrite coil, iron core coil, copper core coil. Classification
by working properties: antenna coil, oscillation coil, choke coil, trap coil, deflection coil.
Classification by winding structure: single-layer coil, multi-layer coil, honeycomb coil.
2. Main characteristic parameters of inductor coils
1. Inductance L
Inductance L represents the inherent characteristics of the coil itself, which has nothing to do with the current size. Except for special inductor coils (color-coded inductors), the inductance is generally not specifically marked on the coil, but marked with a specific name.
2.
Inductive reactance XL The magnitude of the inductor's resistance to AC current is called inductive reactance XL, and the unit is ohm. Its relationship with the inductance L and the AC frequency f is XL=2πfL
3. Quality factor Q
The quality factor Q is a physical quantity that represents the quality of the coil. Q is the ratio of the inductive reactance XL to its equivalent resistance, that is: Q=XL/R
The higher the Q value of the coil, the smaller the loss of the loop. The Q value of the coil is related to factors such as the DC resistance of the wire, the dielectric loss of the skeleton, the loss caused by the shielding cover or the iron core, and the influence of the high-frequency skin effect. The Q value of the coil is usually tens to hundreds.
4. Distributed
capacitance The capacitance between the turns of the coil, between the coil and the shielding cover, and between the coil and the bottom plate is called distributed capacitance. The existence of distributed capacitance reduces the Q value of the coil and deteriorates the stability, so the smaller the distributed capacitance of the coil, the better.
3. Commonly used coils
1. Single-layer coil

Single-layer coils are made by winding insulated wires one by one on a paper tube or bakelite frame. For example,
the wave antenna coil in a transistor radio.
2. Honeycomb coils
If the plane of the wound coil is not parallel to the rotating plane, but intersects at a certain angle, this coil
is called a honeycomb coil. The number of times the wire bends back and forth during one rotation is often called the number of inflection points.
The advantages of honeycomb winding are small size, small distributed capacitance, and large inductance. Honeycomb coils are all
wound using honeycomb winding machines. The more inflection points, the smaller the distributed capacitance.
3. Ferrite core and iron powder core coils
The inductance of the coil is related to whether there is a magnetic core. Inserting a ferrite core into an air-core coil can increase the inductance
and improve the quality factor of the coil.
4. Copper core coils
Copper core coils are widely used in the ultra-short wave range. The inductance is changed by rotating the position of the copper core in the coil.
This adjustment is more convenient and durable.
5. Color-coded inductors
Color-coded inductors are inductors with fixed inductance. Their inductance
is marked with color rings in the same way as resistors.
6. Chokes:
The coils that limit the passage of alternating current are called chokes. They are divided into high-frequency chokes and low-frequency chokes.
7. Deflection coils
The deflection coils are the loads of the output stage of the TV scanning circuit. The deflection coils have the following requirements: high deflection sensitivity,
uniform magnetic field, high Q value, small size, and low price.

Reference address:Inductor Coil

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