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Main characteristic parameters of the inductor

1 inductance L and accuracy
The inductance L represents the inherent characteristics of the coil itself, regardless of the current magnitude. In addition to the special inductor (color code inductor), the inductance is generally not marked on the coil, but marked with a specific name. The inductance of the coil is mainly determined by the diameter of the coil, the number of turns, and the presence or absence of a core. Inductor coils have different uses and require different amounts of inductance. For example, in a high frequency circuit, the inductance of the coil is generally 0.1uH-100Ho.

The accuracy of the inductance, that is, the error between the actual inductance and the required inductance, depends on the application. The oscillation coil is required to be high, o. 2-o. 5%. The coupling coil and high frequency choke are required to be low, allowing 10-15%. For some applications where the accuracy of the inductance is very high, it can only be tested by the instrument after winding, by adjusting the distance between the turns of the edge near the edge or the position of the core in the coil.
2 Sense XL
The size of the inductive coil that blocks the AC current is called XL, and the unit is ohm. Its relationship with inductance L and AC frequency f is XL=2πfL
3 quality factor Q
Coil quality factor
The quality factor Q is used to indicate the amount of coil loss, and the high frequency coil is usually 50-300. The Q value of the tuning loop coil is relatively high, and the resonant circuit composed of the coil of high Q value and the capacitor has better resonance characteristics; the resonant circuit composed of the low Q coil and the capacitor has no obvious resonance characteristic. For coupling coils, the requirements can be lower, and there is no requirement for high frequency chokes and low frequency chokes. The size of the Q value affects the selectivity, efficiency, filtering characteristics, and frequency stability of the loop. Generally, it is desirable to have a large Q value, but it is not an easy task to increase the Q value of the coil. Therefore, appropriate requirements should be made for the Q value of the coil according to the actual use occasion.
The quality factor of the coil is:
Q=ωL/R where:
Ω——working angle frequency;
L——the inductance of the coil;
R——The total loss of the coil The total loss resistance of the resistance coil is composed of DC resistance, high-frequency resistance (caused by skin effect and proximity effect), and dielectric loss. "
In order to improve the quality factor Q of the coil, silver-plated copper wire can be used to reduce the high-frequency resistance; a single-strand wire with the same presidential surface can be replaced by a plurality of insulated wires to reduce the skin effect; Frequency porcelain is the skeleton to reduce dielectric loss. The use of the magnetic core increases the core loss, but can greatly reduce the number of turns of the coil, thereby reducing the DC resistance of the wire, which is advantageous for increasing the Q value of the coil.

The quality factor Q is a physical quantity indicating the quality of the coil, and Q is the ratio of the inductive reactance XL to its equivalent resistance, that is, Q = XL / R. The higher the Q value of the coil, the smaller the loss of the loop. The Q value of the coil is related to the DC resistance of the wire, the dielectric loss of the skeleton, the loss caused by the shield or the iron core, and the influence of the high frequency skin effect. The Q value of the coil is usually from several tens to several hundreds. With the magnetic core coil, multiple thick coils can increase the Q value of the coil.
4 distributed capacitance
The capacitance between the turns and turns of the coil, between the coil and the shield, and between the coil and the master is called a distributed capacitance. The presence of the distributed capacitance reduces the Q value of the coil and the stability is deteriorated, so the smaller the distributed capacitance of the coil, the better. The segmented winding method reduces the distributed capacitance.
5 inherent capacitance
There is a distributed capacitance between the turns of the coil winding, and there is also a distributed capacitance between the multilayer winding layer and the layer. These distributed capacitors can be equivalent to a capacitor Co in parallel with the coil.
6 Allowable error: The percentage of the difference between the actual value of the inductance and the nominal divided by the nominal value.
7 Nominal current: refers to the current allowed by the coil, usually expressed by the letters A, B, C, D, E, the nominal current value is 50mA, 150mA, 300mA, 700mA, 1600mA.

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