Inductor (also known as Choke) is a component that can convert electrical energy into magnetic energy and store it.

Inductors are similar in construction to transformers, but with only one winding. Inductance has a certain inductance, it only hinders the change of current. If the inductor is in a state where there is no current flowing, it will try to block the current flow through it when the circuit is on; if the inductor is in a state where current is passing, it will try to maintain the current when the circuit is off. Inductors are also called chokes, reactors, dynamic reactors and so on.

01． Principle of Inductor

When current flows through the wire, a magnetic field in the shape of concentric circles will be generated with the wire as the center. At this time, if the wire is bent into a "spring shape", the magnetic flux inside the inductor will point in the same direction, thereby strengthening it. By adjusting the number of turns, a magnetic field proportional to the number of turns can be generated. This is how an inductor works.

Current flowing through an inductor produces a magnetic field, and conversely, a change in the magnetic field produces a current.

The counter electromotive force E generated in the inductor is proportional to the rate of change of current per unit time (di/dt), so it does not occur when a constant current continues to flow in the same direction as a direct current. That is to say, the inductor has no effect on DC current, but only acts as a barrier to AC current. Utilizing this property of an inductor, it can be used as a resistor (impedance) in an AC circuit. The impedance Z (unit Ω) of the inductor is: Z=ωL=2πfL

f: AC frequency

L: Self-inductance of the inductor

Inductors (coils) are electronic components known as the three major passive components together with resistors and capacitors. Utilizing the characteristics of the coil to the current, it plays an important role in power supply circuits, general signal circuits, high-frequency circuits, etc.

02． Composition of Inductors

Inductors are generally composed of skeletons, windings, shields, packaging materials, magnetic cores or iron cores.

Skeleton generally refers to the frame on which the coil is wound. Some larger fixed inductors or adjustable inductors (such as oscillating coils, choke coils, etc.), most of them wrap enameled wires (or yarn-covered wires) around the skeleton, and then wrap the magnetic core or copper core, iron The core, etc. are loaded into the inner cavity of the skeleton to increase its inductance. The skeleton is usually made of plastic, bakelite, and ceramics, and can be made into different shapes according to actual needs. Small inductors (such as color-coded inductors) generally do not use a bobbin, but directly wind the enameled wire on the magnetic core.

Winding refers to a group of coils with specified functions, which is the basic component of inductors. There are single-layer and multi-layer windings. There are two forms of single-layer winding: close winding (the wires are next to each other when winding) and inter-winding (there is a certain distance between each circle of wires when winding); multilayer windings have layered flat winding and random winding. There are many kinds of winding, honeycomb winding and so on.

Magnetic cores and magnetic rods are generally made of nickel-zinc ferrite (NX series) or manganese-zinc ferrite (MX series). Various shapes.

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

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 oscillating coil of a semiconductor radio, etc.) is added to it. Using shielded inductors will increase the loss of the coil and reduce the Q value. Packaging material

After some inductors (such as color code inductors, color ring inductors, etc.) are wound, the coils and cores are sealed with packaging materials. The packaging material is plastic or epoxy resin.