What is a tunable inductor? The structure and characteristics of common inductors!

In this article, the editor will introduce the structure and characteristics of tunable inductors and common inductors. If you want to know the details of inductors, or want to improve your understanding of inductors, you may wish to read the following content Oh.

1. What is an inductor

An inductor is a component that can convert electrical energy into magnetic energy and store it. The structure of an inductor is similar to that of a transformer, but with only one winding. An inductor has a certain inductance, it only resists changes in current flow. If the inductor is in a state with no current flowing through it, it will try to block the flow of current through it when the circuit is on; if the inductor is in a state with current flowing through it, it will try to maintain the current flow when the circuit is off. Inductors are also called chokes, reactors, and dynamic reactors.

2. Second, the adjustable inductor of the inductor

Commonly used adjustable inductors include oscillating coils for semiconductor radios, line oscillating coils for TV sets,

Line linear coil, intermediate frequency trap coil, frequency compensation coil for audio, wave blocking coil, etc.

1. Oscillating coil for semiconductor radio: This oscillation coil forms a local oscillation circuit in a semiconductor radio with variable capacitors, etc., and is used to generate a local oscillator signal, which is input to the radio received by the tuning circuit Signals above 465kHz. The outside is a metal shield, and the inside is a nylon-lined frame, I-shaped core, magnetic cap, and pin holder. The winding of the I-shaped core is made of high-strength enameled wire. The magnetic cap is mounted on the nylon frame of the shield, which can be rotated up and down, and the inductance of the coil can be changed by changing the distance between the magnetic cap and the coil. The internal structure of the TV IF trap coil is similar to the oscillating coil, except that the magnetic cap is adjustable.

2. Line oscillating coils for TV sets: Linear oscillating coils were used in early black and white TV sets. It forms a self-excited oscillation circuit (three-point oscillator or intermittent oscillator, multivibrator) together with the peripheral resistor capacitor assembly and the line oscillation transistor to generate a rectangular pulse voltage signal with a frequency of 15625HZ.

There is a square hole in the center of the coil core, and the horizontal synchronization adjustment knob is directly inserted into the square hole. By rotating the horizontal synchronization adjustment knob, the relative distance between the magnetic core and the coil can be changed, so as to change the inductance of the coil and keep the horizontal oscillation frequency at 15625HZ, and generate synchronous oscillation through the automatic frequency control transmission line synchronization pulse circuit (AFC).

3. Line linear coil: Line linear coil is a non-linear magnetic saturation inductance coil (its inductance decreases with the increase of current). It is usually connected in series in a line deflection coil loop and utilizes its magnetic saturation properties to compensate for linear distortion of the image.

The linear coil consists of an I-shaped ferrite high-frequency core or ferrite bar made of enameled wire, and an adjustable permanent magnet is installed next to the coil. By changing the relative position of the permanent magnet and the coil to change the size of the coil inductance, so as to achieve the purpose of linear compensation.

3. The structure and characteristics of commonly used inductors

(1) Single layer wire. Single-layer air-core coils are made by winding an insulated wire round after round. The coil can be wound on an insulating bobbin, such as a paper tube, plastic bobbin or bakelite bobbin, or can be wound without a bobbin. Air core coils are often used in high frequency circuits. High frequency coils (eg shortwave) are usually wound by indirect windings.

(2) Copper core coil. Copper core coils are widely used in the ultrashort wave range. The position of the copper core in the coil is used to change the inductance. This adjustment is more convenient and durable.

(3) Color-coded inductor coil. A color-coded inductor coil is a high-frequency inductor coil manufactured by wrapping some enameled wire around a magnetic core and encapsulating it with epoxy or plastic. Color-coded inductors are inductors with fixed inductance, whose inductance marking method is marked with a color ring. Color-coded inductors are easily mounted on printed circuit boards. Its inductance is usually between 0.luH to 3300uH, and its operating frequency is 10KHz to 200MHz.

(4) Honeycomb coil. A honeycomb coil is a coil that is wound whose planes are not parallel to the surface of revolution, but intersect at an angle. The advantages of the honeycomb winding method are small size, small distributed capacitance and large inductance.

(5) Deflection coil. The deflection yoke is the load for the output stage of the TV scanning circuit used in TV sets using CRT cathode ray tubes. The requirements of the deflection coil are: high deflection sensitivity, uniform magnetic field, high Q value, small size and low price.

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