Inductor characterization

[dtvmcdonald]

While thinking of the "white crud" coil problems of CT-100s, I
thought of "how do you adequately characterize an inductor?"
so one that matches that characterization "just works".

It would seem that you need four numbers:

1) Inductance at low frequency

2) DC resistance

3) parallel resonant frequency

4) Q at parallel resonant frequency

I was also thinking that for air core coils #4 might
be superfluous. Clearly for magnetic core ones it, or something like it,
such as Q if resonated at the expected operating frequency,
is necessary. It would also be necessary for shielded coils.

Does anybody KNOW the answer to whether this is good enough?

Doug McDonald

[bob91343]

How about inductance vs. direct current? Q at low frequency? And Q at resonance has little meaning, since by definition there is no reactance there, and Q is defined at reactance divided by resistance.

[dtvmcdonald]

Ah, you are right about inductance versus DC in non-air-core coils.

You're wrong about Q at resonance, since resonance is a two-part thing:
Inductance with effective resistance in parallel with essentially
perfect capacitance. The Q is that of the inductor alone.