Inductance coils are also one of the commonly used components in household appliances, instruments and other electronic products, and are electronic components that use the principle of electromagnetic induction to work. Its electrical characteristics are opposite to that of capacitors, "passing low frequencies and blocking high frequencies". High-frequency signals will encounter great resistance when passing through the inductance coil, making it difficult to pass; while the resistance presented by low-frequency signals passing through it is relatively small, that is, low-frequency signals can pass through it easily. The resistance of the inductor to direct current is almost zero.

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

In the circuit diagram, the inductance coil is represented by the letter L.

Classification of inductance coils

There are many types of inductance coils, and their classification methods are different.

According to the line core classification, it can be divided into air core inductance coil, magnetic core inductance coil, iron core inductance coil and copper core inductance coil.

According to the type of installation, it can be divided into vertical and horizontal inductance coils.

According to the working frequency classification, it can be divided into high frequency inductance coil, medium frequency inductance coil, and low frequency inductance coil.

Classified by purpose, it can be divided into power filter coils, high frequency filter coils, high frequency choke coils, low frequency choke coils, line deflection coils, field deflection coils, line oscillation coils, line linearity correction coils, local oscillation coils, High frequency oscillating coil.

According to whether the inductance is adjustable or not, it can be divided into fixed inductance coils, variable inductance coils, and fine-tuning inductance coils.

According to the winding method and its structure classification, it can be divided into single-layer, multi-layer, honeycomb, skeleton and non-skeleton inductor coils.

Inductor model naming method

The model of the inductance coil is mainly composed of four parts: main name, feature, type, and distinguishing code:

The first part: the main name, L represents the coil, ZL represents the choke coil;

The second part: features, use G to represent high frequency;

The third part: type, use X to indicate small size;

The fourth part: distinguish the code, use the letters A, B, C, etc.

For example, LGX stands for small plastic high frequency inductance coil.

Main characteristic parameters of inductance coil

1. Inductance

The inductance refers to the size of the self-inductance generated by the inductance coil when the current passes through it.

The unit of inductance is Henry, which is represented by the letter H. Commonly used units are millihenry (mH) and microhenry (μH). Their conversion relationship is:

2. Quality factor

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

In the formula, w is T as the angular frequency, L is the coil inductance, and R is the total loss resistance of the coil.

3. Rated current

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

4. Distributed capacitance

Distributed capacitance refers to the capacitance formed between the turns of the coil, that is, the capacitance formed by the air, the insulating layer of the wire, and the skeleton. The sum of these capacitances and the resistance of the inductor itself form a resonant circuit, which produces a certain rate of resonance, reduces the stability of the inductor's inductance, and reduces the Q value. Generally, the distributed capacitance should be reduced. In order to reduce the distributed capacitance of the inductance coil, different control methods are generally adopted, such as the indirect winding m