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2022

08
Basic knowledge of inductors
Author：
Zidian Electric
Inductors are commonly referred to as inductors and are one of the most commonly used basic electronic components.
There are many types of inductors and different shapes. The more common ones are: singlelayer flatwound aircore inductor coil, spacewound aircore inductor coil, unwrapped aircore coil, multilayer aircore inductor coil, honeycombtype inductor coil, with magnetic core Inductance coil, magnetic tank inductance coil, high frequency choke coil, low frequency choke coil, fixed inductor, etc.
The main uses of inductors in circuits: one is used for circuit tuning, such as tuning coils in radios and resonant coils of intermediate frequency transformers, etc.; the other is used in oscillating circuits, such as oscillating coils in radios, and various LC oscillations The inductance coil in the circuit; the third is used for blocking filtering, such as the LC filter inductor used for power supply filtering; the fourth is the resonant inductor used for frequency selection in bandpass and bandrejection filters.
The inductance coil is wound on an insulating tube with wires one by one, and the wires are insulated from each other, and the insulating tube can be hollow or contain an iron core or a magnetic powder core.
As a kind of inductance components, the inductance coil has a wide range of applications. Most of the inductance coils are nonstandard components and can be wound by yourself. So how should the inductance coil be wound, and what are the winding methods of the inductance coil? The total winding method of the coil includes a singlelayer winding method and a multilayer winding method, which are respectively suitable for the winding of different inductances. Among them, the singlelayer winding method and the multilayer winding method have different winding methods. You introduce specific details.
The winding method of the enameled wire of the inductor coil on the skeleton can be divided into two types: singlelayer winding method and multilayer winding method.
The first winding method: singlelayer winding method
The singlelayer inductance coil is one of the most widely used in today's circuit applications, and its inductance is generally only a few or dozens of microhenries. The Q value of such coils is generally relatively high, and most of them are used in highfrequency circuits.
In the design of singlelayer inductance coil, its line winding method usually adopts three methods: close winding method, intermediate winding method and freeform winding method. And these three winding methods are also suitable for different circuit appliances.
1. The dense winding method is actually to place the wires next to each other and densely wound them on the skeleton. This coil inductance is usually used in antennas, such as the antenna coils of radios and semiconductor tape recorders.
2. The winding method of the intermediate winding method is generally similar to that of the dense winding method, except that there are gaps between the coils, instead of being close to each other like the dense winding method. This inductance has small distributed capacitance and high highfrequency performance, and is very suitable for use as a shortwave antenna.
3. The coil of the freewound method is actually a hollow coil, which can also be said to be a deformation of the closewound method, that is, the skeleton of the closewound method is pulled out, and the gap between each coil is appropriately adjusted according to the required indicators, or directly. Change the shape of the coil. It is generally used as a resonant circuit in high frequency circuits.
The second winding method: multilayer winding method
Singlelayer coils can only be used in applications with small inductance, so when the inductance is greater than 300μH, multilayer coils should be used.
The multilayer winding method can be divided into multilayer dense and honeycomb winding methods: if the winding of the honeycombtype inductance coil is wound, its plane is not parallel to the rotating surface, but intersects at a certain angle. It is called a honeycomb coil. The number of times the wire is bent back and forth during one rotation is often referred to as the number of inflection points. The advantages of the honeycomb winding method are small size, small distributed capacitance, and large inductance.
Inductors work using the principle of selfinduction. The inductive coil will generate a selfinduced electromotive force when passing current, and the magnitude of the selfinduced electromotive force is proportional to the rate of change of the current passing through the inductive coil, and always opposes the change of the original current (Figure 6). Therefore, the inductor has the function of passing DC and blocking AC.
The quality of the inductor can be tested with a multimeter. Put the multimeter in the "R×1" block, and connect the two test leads (regardless of positive and negative) to the two pins of the inductor. The pointer indication should be close to "0Ω". resistance. If the needle does not move, it means that the inductor has an internal circuit breaker; if the needle indicates unstable, it means that the internal contact is poor.
Well, that's it for today's knowledge of inductors. If you have any suggestions, you can leave a message below for discussion, and Zidianjun will reply one by one.
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