1. What is an inductor

 An inductor is an element that can convert electrical energy into magnetic energy and store it. The structure of the inductor is similar to that of a transformer, but there is only one winding. The inductor has a certain inductance, which only hinders the change of current. When the inductor is not connected, it will block the current flowing through the circuit; If the inductor is in a state of current flow, it will try to keep the current constant when the circuit is disconnected. Inductor is also called choke, reactor and dynamic reactor.

 

2. Structure of inductor

 Inductors are generally composed of skeleton, winding, shielding cover, packaging material, magnetic core or iron core, etc.

 1. Skeleton generally refers to the support for winding coils. For some fixed inductors or adjustable inductors with large volume (such as oscillation coil, choke ring, etc.), most of them wrap enamelled wire (or yarn wrapped wire) around the skeleton, and then install the magnetic core, copper core and iron core into the inner cavity of the skeleton to improve its inductance. The skeleton is usually made of plastic, bakelite and ceramics, which can be made into different shapes according to the actual needs. Small inductors (such as color code inductors) generally do not use a skeleton, but directly wrap the enameled wire around the magnetic core. Hollow inductors (also known as bodiless coils or hollow coils, which are mostly used in high-frequency circuits) do not use magnetic cores, frameworks and shielding covers. Instead, they are wound on the mold first, and then take off the mold, and pull a certain distance between the coils.

 2. Winding refers to a group of coils with specified functions, which is the basic part of inductor. The winding can be divided into single layer and multi-layer. The single-layer winding has two forms: close winding (when winding, the wires are next to each other) and inter winding (when winding, each wire is separated by a certain distance); There are many kinds of multilayer windings, such as layered flat winding, random winding, honeycomb winding and so on.

 3. Magnetic core and magnetic rod magnetic core and magnetic rod are generally made of nickel zinc ferrite (NX Series) or manganese zinc ferrite (MX Series) and other materials, which have "I" shape, column shape, cap shape, "e" shape, tank shape and other shapes.

 4. The iron core materials mainly include silicon steel sheet, permalloy, etc., and its shape is mostly "e".

 5. In order to prevent the magnetic field generated by some inductors from affecting the normal operation of other circuits and components, a metal screen cover (such as the oscillation coil of semiconductor radio) is added to the shielding cover. The inductor with shielding cover will increase the loss of the coil and reduce the Q value.

 6. Packaging materials after winding some inductors (such as color code inductor, color ring inductor, etc.), seal the coil and magnetic core with packaging materials. The packaging material is plastic or epoxy resin.

 

Inductance classification

 Self sensor

 When a current passes through the coil, a magnetic field will be generated around the coil. When the current in the coil changes, the magnetic field around it also changes accordingly. The changed magnetic field can make the coil produce induced electromotive force (induced electromotive force) (electromotive force is used to represent the terminal voltage of the ideal power supply of the active element), which is self induction.

 An electronic component, which is wound by a conductor and has a certain number of turns and can produce a certain amount of self inductance or mutual inductance, is often called an inductive coil. In order to increase the inductance value, improve the quality factor and reduce the volume, iron core or magnetic core made of ferromagnetic material is often added. The basic parameters of inductor include inductance, quality factor, inherent capacitance, stability, passing current and service frequency. The inductor composed of a single coil is called self inductor, and its self inductance is also called self inductance coefficient.

 Transformer

 When two inductance coils are close to each other, the magnetic field change of one inductance coil will affect the other inductance coil, which is mutual inductance. The size of mutual inductance depends on the degree of coupling between the self inductance of the inductance coil and the two inductance coils. The element made by using this principle is called mutual inductor.

 

characteristic

 The characteristics of inductor are just opposite to those of capacitor. It has the characteristics of preventing AC from passing through and allowing DC to pass smoothly. When the DC signal passes through the coil, the resistance is the resistance of the conductor itself, and the voltage drop is very small; When the AC signal passes through the coil, the self induced electromotive force will be generated at both ends of the coil. The direction of the self induced electromotive force is opposite to the direction of the applied voltage, which hinders the passage of AC. therefore, the characteristics of the inductor are DC and ac. the higher the frequency, the greater the coil impedance. Inductors often work with capacitors in circuits to form LC filters, LC oscillators, etc. In addition, people also use the characteristics of inductance to manufacture choke coil, transformer, relay and so on.

 Direct current: it means that the inductor is closed to the direct current. If the resistance of the inductive coil is ignored, the direct current can pass through the inductor "unimpeded". For the direct current, the resistance of the coil itself is very small, and the blocking effect on the direct current is very small, so it is often ignored in the circuit analysis.

 AC resistance: when the AC passes through the inductive coil, the inductor hinders the AC. what hinders the AC is the inductive reactance of the inductive coil.

 

Functional use

 Inductors mainly play the role of filtering, oscillation, delay and notch in the circuit, as well as screening signals, filtering noise, stabilizing current and suppressing electromagnetic wave interference. The most common function of inductance in circuit is to form LC filter circuit together with capacitance. The capacitance has the characteristics of "blocking DC and connecting AC", while the inductance has the function of "connecting DC and blocking AC". If the DC current with many interference signals is passed through the LC filter circuit, the AC interference signal will be consumed by the inductor into heat energy; When the relatively pure DC current passes through the inductor, the AC interference signal is also transformed into magnetic induction and thermal energy. The higher frequency is most likely to be impedance by the inductor, which can suppress the higher frequency interference signal.

 The inductor has the characteristics of preventing the passage of AC and allowing the smooth passage of DC. The higher the frequency, the greater the coil impedance. Therefore, the main function of the inductor is to isolate and filter the AC signal or form a resonant circuit with capacitors and resistors.

 To sum up, do you have a certain understanding of inductors? If you have any questions and needs, please feel free to contact us and give you the most professional opinions