■ 问题的提出

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为什么 使用RLC表测量电感在不同的频率下所测量得到的电感不同呢？ .

^{▲ TH2821A RLC表以及测量电感|电感来自于一个继电器的线圈}

选取了 一个继电器线圈 使用便携RLC表 TH2821A 对其进行电感测量。使用不同的频率测量的结果如下：

测量频率	电感值
100Hz	337.5mH
120Hz	301.7mH
1kHz	156.7mH
10kHz	75.74mH

选取另外一个小型的工字型磁芯电感进行测量。

^{▲ 一个小型10mH的磁芯电感}

测量频率	电感值
100Hz	64.7mH
120Hz	47.82mH
1kHz	10.19mH
10kHz	9.55mH

从前面两个例子来看，无论是铁芯的继电器电感，还是磁芯的电感，它们的电感值都与所使用测量频率有关系。随着测量频率的提高，对应的电感量下降。那么这究竟为什么呢？

 

01问题的解释

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为网站eevblog 有一个帖子 LRC Meter - Different readings at different frequencies - Why? - Page 1 给出了一些答案。下面的回复我认为是比较全面的概括了不同的频率对测量电感的影响。也比较符合前面测量的结果的分析：

• 网页摘抄

If the inductor being measured is not an air core type, the permeability of the core material may well change with frequency. And, for that matter, the permeability may change with the applied test signal level. Ferrite material is perhaps the most well known for permeability change with frequency, but it’s not the only material.

Second order effects also causes change in inductance with frequency - for example as the frequency increases, the current distribution on the wire an inductor is wound with changes. Skin effect drives the current to the outside of the conductor and proximity effect drives current away from the conductors surfaces that are adjacent. These effects are small in many cases but they alter the equivalent dimensions of the inductor and hence the physical flux linkages and therefore the inductance.

Finally, as has been mentioned, all practical inductors have self-capacitance. At some frequency, the inductor becomes self-resonant where the distributed capacitance and inductance form a parallel resonant circuit. As you measure an inductor with a variable frequency source, the closer you are to the SRF, the greater the indicated inductance. At the SRF, the indicated inductance is 0 and above the SRF, the sign inverts and the instrument indicates you are measuring a capacitor, not an inductor.

It is possible to “de-embed” these various parasitic effects and model a real inductor as a network of theoretically perfect parts, none of which change with frequency. So in one sense, it is correct to say that the “inductance does not change with frequency” provided that you mean one part of the model of a real world inductor. However, if one conceptualizes the real world inductor as a black box it is just as accurate to say that the box contains an inductor with parameters that are a function of frequency (and applied test signal level, etc.)

 

※ 结论

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根据前面讨论，可以知道一个具有导磁磁芯的电感，特别是铁芯电感会因为不同的频率而具有不同的电感值。因此，最好是使用在实际工作中相同或者相近的频率来测量电感的电感量。

也可以使用在 磁铁与悬浮 中根据波形来测量电感的数值。