Inductors, also known as chokes, reactors, and dynamic reactors. It is an element that can convert electric energy into magnetic energy and store energy in the magnetic field. The structure is similar to the transformer and has the characteristics of DC and AC resistance. In electronic circuits, inductance mainly plays the role of filtering, current limiting, tuning, oscillation, interference suppression and magnetic field generation. Inductance units and parameters mainly include the following aspects: The symbol l indicates that the basic unit of the inductor is Henry (H), which is commonly used in milli Heng (MH) and micro Heng（ μ H) Is the unit. Conversion relationship: 1h=10^3mh=10^6 μ H。 That is, the unit conversion is generally 10 cubic. Inductance is divided into general inductance and precision inductance; General inductance: the error value is 20%, expressed in M; The error value is 10%, expressed in K. Precision inductance: the error value is 5%, represented by J; The error value is 1%, expressed in F. For example, 100k is 10 μ H. The error is 10%. Inductance can be made of conductive material coiled around the magnetic core, typically copper wire, or the magnetic core can be removed or replaced with ferromagnetic material. The core material with higher permeability than air can restrict the magnetic field more closely around the inductive element, thus increasing the inductance. The chips of some inductive components can be adjusted. Thus, the inductance can be changed. The small inductor can be directly etched on the PCB board with a method of laying spiral tracks. Small value inductors can also be used to make transistors. The same process is used in integrated circuits. In these applications, aluminum interconnects are often used as conductive materials. No matter what method is used, based on the actual constraints, the most widely used is a circuit called "spinner", which uses a capacitor and an active element to show the same characteristics as the inductive element. Inductive elements used to isolate high frequencies are often composed of a metal wire passing through a magnetic column or bead. Inductors can also be divided into self inductors and mutual inductors. When there is current flowing 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 correspondingly. The changed magnetic field can make the coil generate 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 called self inductor. 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.
Inductors are components that can convert electrical energy into magnetic energy and store it. The structure of inductor is similar to that of transformer, but there is only one winding. The inductor has a certain inductance, which only blocks the change of current. Inductance can be made of conductive material coiled around the magnetic core, typically copper wire, or the magnetic core can be removed or replaced with ferromagnetic material. The core material with higher permeability than air can restrict the magnetic field more closely around the inductive element, thus increasing the inductance. There are many kinds of inductors, most of which are made of the outer enamel coil surrounding the ferrite spool, while some protective inductors place the coil completely in the ferrite. The cores of some inductive elements can be adjusted. Thus, the inductance can be changed. The small inductor can be directly etched on the PCB board with a method of laying spiral tracks. Small value inductors can also be used to make transistors. The same process is used in integrated circuits. In these applications, aluminum interconnects are often used as conductive materials. No matter what method is used, based on the actual constraints, the most widely used is a circuit called "spinner", which uses a capacitor and an active element to show the same characteristics as the inductive element. Inductive elements used to isolate high frequencies are often composed of a metal wire passing through a magnetic column or bead. There are many kinds of inductors with different shapes. The more common ones are: single-layer flat wound hollow core inductors, inter wound hollow core inductors, bodiless hollow core inductors, multi-layer hollow core inductors, honeycomb inductors, inductors with magnetic cores, magnetic can inductors, high-frequency choke coils, low-frequency choke coils, fixed inductors, etc. The winding method of enameled wire of inductance coil on the skeleton can be divided into single-layer winding method and multi-layer winding method. The first winding method: single layer winding method Single layer inductance coil is widely used in today's circuit applications, and its inductance is usually only a few or dozens of micro Heng. The Q value of this kind of coil is generally high, and most of them are used in high-frequency circuits. In the design of single-layer inductance coil, its circuit winding method usually adopts close winding method, intermediate winding method and tire free winding method. These three winding methods are also applicable to different circuit appliances. The second winding method: multi-layer winding method Single layer coil can only be used in occasions with small inductance, so when the inductance is greater than 300 μ H, multilayer coils should be used. The multi-layer winding method can be divided into two types: multi-layer dense winding method and honeycomb winding method: if the coil is wound, its plane is not parallel to the rotating surface, but intersects into a certain angle, this kind of coil is called honeycomb coil. The number of times the wire bends back and forth when it rotates for one cycle is often called the number of turns. The advantages of honeycomb winding method are small volume, small distributed capacitance and large inductance.
Inductors mainly play the role of filtering, oscillation, delay, notch, etc. in the circuit, as well as screening signals, filtering noise, stabilizing current and suppressing electromagnetic wave interference. According to the product characteristics of inductors, it generally includes the following common sense and terms, which you must understand. DC resistance, DC resistance is the resistance value measured under DC. The higher the resistance, the greater the power loss. The smaller the DC resistance of various inductors for resonance, impedance matching and choke, the better. Self resonant frequency refers to the frequency when the coil itself resonates with its own capacitance. If the resonant frequency is exceeded, the inductor will not work. The self resonant frequency of various inductors for resonance, impedance matching and choke shall be greater than the working frequency. DC superposition characteristic refers to the inductance characteristic of superimposing DC current on micro AC current. Allowable current / rated current. Allowable current refers to the maximum DC current that can pass through the coil without damaging the element. If the current exceeds the allowable current, too much heat will be generated and the quality cannot be guaranteed. The allowable current of the choke inductor must be greater than the maximum current when the circuit is working. Working temperature range refers to the allowable range of ambient temperature when the inductor is working. The operating temperature range does not include naturally generated heat. The working temperature range of various inductors for resonance, impedance matching and choke must be within the working temperature range of the equipment. Magnetic saturation, if a magnetic field is applied to magnetic substances such as ferrite, magnetic flux will be generated. The inductance of the inductor depends on the degree of the magnetic flux. The stronger the magnetic field, the smaller the increase of magnetic flux corresponding to the magnetic field. Even if the magnetic field is enhanced, the magnetic flux will not increase. This is the phenomenon of magnetic saturation of magnetic substances. From the point of view of the inductor, as the current through the inductor increases, the magnetic field will also increase, so there will be magnetic saturation of magnetic substances, and as a result, the inductance value will decrease. Since the magnetic saturation characteristics of inductors depend on the type and structure of magnetic materials used by inductors, and inductors used in power supply systems pass a large current, it becomes very important whether magnetic saturation is easy to occur. In order to confirm its degree, refer to the DC superposition characteristics of inductors.