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I was trying out a series RLC band stop filter on hardware but for some reason it was not working, I later figured out that the culprit was the inductor after testing both inductor and capacitor via the RC and RL filters, I tried different inductors of the same kind, even of different values of inductance but they yielded no success till I used the coil that is usually found in energy savers, and then the filter worked perfectly, so is it that the inductors like these that i used previously have some sort of limitation in the amount of current that can pass through them or are they not good for filters?

I had used Vpk =1V from a function generator and R=1Kohms The inductor values that I had checked ranged from 20 micro Henry to 25 milli Henry, sorry I cannot tell you the model number or anything else because in my area, 98% of electronic shops just sell these in local cardboard boxes, the boxes just contain inductors of some specific value that they have bought and placed in the box

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    \$\begingroup\$ There is a limitation in the amount of current that can pass through most things. Did you check what these ones could handle? \$\endgroup\$ – MCG Jul 12 '17 at 13:52
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    \$\begingroup\$ Values and part numbers please. A schematic of the circuit, and the expected behavior with operating conditions, is always useful as well. \$\endgroup\$ – Chris Knudsen Jul 12 '17 at 13:58
  • \$\begingroup\$ @MCG and chris, sorry guys I have no part numbers because shops in my town just sell them in open boxes but the ranges that I had checked were from 20 micro henry to 25 milli henry \$\endgroup\$ – Syed Mohammad Asjad Jul 12 '17 at 14:11
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    \$\begingroup\$ what are your specs f, Q? All passives have a self resonant frequency SRF, and Q value, even if unspecified. RF parts all have these specs. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Jul 12 '17 at 14:17
  • \$\begingroup\$ RLC filter at what frequency? What frequency did you test them at? How did you measure the voltage over or current though your resistor in your test setup? \$\endgroup\$ – winny Jul 12 '17 at 14:21
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Of the three basic passive components (Resistors, capacitors, inductors) found on your shop's shelves, inductors are least ideal. Where the box label says "200 uH", you should recognize that the shop owner has likely measured it with an instrument under very specific conditions - likely differing greatly from your intended use.
Resistors and capacitors have much more dominant primary properties (resistance for resistors, capacitance for capacitors) than inductors. Notice the queries from other responders, who have all identified things that influence the success of the filter using your inductor: frequency, current levels, wire resistance, capacitance between turns of wire.

For your specific application (band-stop filter), your inductor choice might consider:

  • Does the inductor have to deal with high power levels?

  • Is the inductor designed to be used at your filter's band-stop frequency?

  • How much attenuation is your band-stop filter expected to achieve?
  • What frequency accuracy is expected at the filter's suck-out frequency?

A high-performance band-stop filter, requiring great attenuation at a very precise frequency likely requires a high-quality inductor having an accurate inductance that doesn't vary with temperature. A tiny inductor might be wound on ferrite that can easily saturate at high power levels. Resistance of the inductor at your filter design frequency may be far higher than resistance measured with a DC ohmmeter. Inter-winding (parasitic) capacitance can cause its inductance to vary greatly at different frequencies. It is not worth your shop-owners time to characterize all these effects.

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  • \$\begingroup\$ I was having the same feeling that inductors might be the most prone to be unworthy because of all the factors, thanks for clearing it up :) \$\endgroup\$ – Syed Mohammad Asjad Jul 12 '17 at 19:01
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Yes. It depends on the inductance value of a coil you use as well as frequency of your input. More the inductance in inductor , slower the current flow. Higher the frequency of signal, inductor attenuate current more or behave like open circuit.

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Current rating and frequency are limiting factors. Resistance in the inductor itself can also be problematic in some cases. Higher power inductors will generally have a lower resistance due to a larger wire size.

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  • \$\begingroup\$ I agree with you, I guess that is why using it from an energy saver bulb had it working \$\endgroup\$ – Syed Mohammad Asjad Jul 12 '17 at 19:04

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