Popularizing common sense inductors

An inductor is also one of widely used components in household appliances, appliances and other electronic products. It is an electronic component that works on principle of electromagnetic induction. Its electrical characteristics are opposite of those of capacitors, "passing low frequencies and blocking high frequencies". When a high frequency signal passes through inductor, it will meet a lot of resistance and it will be difficult to pass through it, while resistance to passage of a low frequency signal is relatively small, that is, a low frequency signal can pass through it more easily. The resistance of inductor coil to direct current is practically zero.

In electronic circuits, an inductor is mainly used to isolate and filter AC signals, or to form a resonant circuit with capacitors and resistors.

In circuit diagram, inductor is marked with letter L.

Classification of inductors

There are many types of inductors, and classification methods vary.

Classified according to wire core, it can be divided into air core inductor coil, magnetic core inductor coil, iron core inductor coil and copper core inductor coil.

Classified according to shape of installation, they can be divided into vertical and horizontal inductors.

Classified by operating frequency, they can be divided into high frequency inductors, medium frequency inductors and low frequency inductors.

Classified by purpose, it can be divided into power filter coils, high-pass filter coils, high-frequency choke coils, low-frequency choke coils, line deflection coils, field deflection coils, linear oscillation coils, linear correction coils, local oscillation coils. coils, high frequency oscillatory coils.

Depending on whether inductance is adjustable, it can be divided into fixed inductance coils, variable inductance coils, and coils with fine inductance adjustment.

According to winding method and structure, inductors can be divided into single-layer, multi-layer, honeycomb, frame and non-frame inductors.

The way inductor models are named

The inductor model mainly consists of four parts: main name, specification, type and difference code:

First part: main name, letter L for coil and ZL for choke coil;

Second part: functions using G to represent high frequencies;

Third part: enter, use X to indicate small size;

Fourth part: recognize codes, use letters A, B, C, etc.

For example, LGX means a small plastic high frequency inductor.

Basic characteristic parameters of an inductor

1. Inductance

Inductance refers to amount of intrinsic inductance that occurs when an inductor conducts current.

The unit of inductance is Henry, denoted by letter H. Commonly used units are millihenry (mH), microhenry (µH). Their conversion ratio:

2. Dignity

The ratio of stored energy to consumed energy in an inductor is called quality factor, also known as Q value, and its definition is:

In formula, w is corner frequency T, L is inductance of coil, and R is loss impedance of coil.

3. Rated current

The rated current of an inductor coil refers to maximum current flowing through an inductor coil during normal operation. The rated current is an important parameter for high frequency, low frequency choke coils and high power resonant coils.

4. Distributed Capacity

Distributed capacitance refers to capacitance formed between turns of coil, that is, capacitance formed by air, insulating layer of wire and frame. The sum of these capacitances and resistance of inductor itself form a resonant circuit that creates a resonance of a certain speed, reduces stability of inductance of inductor and reduces value of Q. Usually, distributed capacitance must be reduced. In order to reduce distributed capacitance of an inductor, various control methods are commonly used, such as interwinding winding method and honeycomb winding method.