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.