The performance index of the inductor coil is mainly the size of the inductance. In addition, the wire that winds the inductor coil generally has a certain resistance, usually this resistance is very small and can be ignored. But when the current flowing in some circuits is very large, the small resistance of the coil cannot be ignored, because a large current will consume power on the coil, causing the coil to heat up or even burn out, so sometimes it must be considered. The electric power that the coil can withstand.

Inductance

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. Inductance is also called self-inductance, which is a physical quantity that represents the self-inductance of inductors. The size of the inductance of the inductor mainly depends on the number of turns (number of turns) of the coil, the winding method, the presence or absence of the magnetic core and the material of the magnetic core, and so on. Generally, the more coil turns and the denser the coils, the greater the inductance. A coil with a magnetic core has a greater inductance than a coil without a magnetic core; the greater the permeability of the magnetic core, the greater the inductance.

The basic unit of inductance is Henry (Henry for short), which is represented by the letter "H". Commonly used units are millihenry (mH) and microhenry (μH).

sensory resistance

The hindering effect of the inductance coil on the alternating current is called the inductive reactance XL, the unit is ohm, and the symbol is Ω. Its relationship with inductance L and alternating current frequency f is XL=2π　　 quality factor

Quality factor Q is a physical quantity that represents the quality of the coil. Q is the ratio of the inductive reactance XL to its equivalent resistance, namely: Q=XL/R. It refers to the ratio of the inductive reactance presented by the inductor to its equivalent loss resistance when it works under a certain frequency of AC voltage. The higher the Q value of the inductor, the smaller its loss and the higher the efficiency. 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. The quality factor of an inductor is related to the DC resistance of the coil wire, the dielectric loss of the coil frame, and the loss caused by the core and shield.

Distributed capacitance

A certain amount of capacitance exists in any inductive coil between turns, between layers, between the coil and the reference ground, between the coil and the magnetic shield, etc. These capacitances are called the distributed capacitance of the inductance coil. If these distributed capacitances are integrated together, it becomes an equivalent capacitance C connected in parallel with the inductance coil. 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.

rated current

Rated current refers to the maximum current value that the inductor is allowed to pass during normal operation. If the working current exceeds the rated current, the inductor will change its performance parameters due to heat, and even burn out due to overcurrent.