1. The definition of inductance

1.1 Definition of inductance:

Inductance is the ratio of the magnetic flux of the wire to the current that produces this magnetic flux when alternating current is passed through the wire, which produces alternating magnetic flux inside and around the wire. L=ψ/I

 

1.2 Symbols and units of inductance

Inductance symbol: L

Inductance units: Hen (H), millihenry (mH), microhenry (uH), nanohenry (nH), 1H=103mH=106uH=109nH.

 

1.3 Classification of inductance:

Classified by inductance form: fixed inductance, variable inductance.

According to the nature of the magnetic conductor: air core coil, ferrite coil, iron core coil, copper core coil.

Classified by work nature: antenna coil, oscillating coil, choke coil, trap coil, deflection coil.

Classified by winding structure: single-layer coil, multi-layer coil, honeycomb coil.

Classified by working frequency: high frequency coil, low frequency coil.

Classified by structural characteristics: magnetic core coil, variable inductance coil, color code inductance coil, non-magnetic core coil, etc.

 

Second, the main characteristic parameters of the inductance

2.1 Inductance L

   The inductance L represents the inherent characteristics of the coil itself and has nothing to do with the magnitude of the current. Except for special inductance coils (color code inductance), the inductance is generally not specifically marked on the coil, but marked with a specific name.

 

2.2 Induction XL

   The hindering effect of the inductance coil on the alternating current is called the inductive reactance XL, and the unit is ohm. The relationship between it and the inductance L and alternating current frequency f is the inductive reactance calculation formula: XL=2πfL

   

 

2.3 Quality factor Q

   The quality factor Q is a physical quantity that represents the quality of the coil, and Q is the ratio of the inductive reactance XL to its equivalent resistance, namely: 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 frame, 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 tens to hundreds. Using magnetic core coils, multiple thick coils can improve the Q value of the coil.

   

2.4 Distributed capacitance

   The capacitance between the turns of the coil, between the coil and the shield, and between the coil and the base plate is called distributed capacitance. The existence of distributed capacitance reduces the Q value of the coil and the stability becomes worse. Therefore, the smaller the distributed capacitance of the coil, the better. Using segment winding method can reduce distributed capacitance.

 

2.5 Allowable error: the percentage of the difference between the actual value of the inductance and the nominal value divided by the nominal value.

 

 2.6 Nominal current: refers to the current allowed by the coil, usually represented by the letters A, B, C, D, and E respectively. The nominal current value is 50mA, 150mA, 300mA, 700mA, 1600mA.