Are Inductors Polarity Sensitive?

Discussion in 'General Electronics Chat' started by robsworld, Nov 22, 2015.

  1. robsworld

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  2. Papabravo

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  3. robsworld

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    Thank-you, I googled my question and most answers were no but a few were yes depending on inductor so I had to ask. :)
     
  4. Papabravo

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    In my qualified answer I said "single inductors" are not polarized. There are sometimes coupled inductors wound on a common core that behave like transformers, and there, polarity can make a difference.
     
  5. robsworld

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    I did notice that and that's what I was reading, didn't know what mine was so here I am. :) Thanks again!
     
  6. Papabravo

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    Well a single inductor should have exactly two leads and measure a low DC resistance with an ohmmeter. If there are more than two visible leads; further investigation is required.
     
  7. WBahn

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    Since you are asking about a specific inductor, how about looking at the data sheet that is linked for that specific inductor?

    The answer will be no because that is just a run-of-the-mill fixed 47 uH, 40 mΩ, 3A inductor, but it is a good opportunity to get some practice finding answers in data sheets.
     
  8. kubeek

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    In theory yes, however in practical use you may want to orient it in the preferred way. The thing is that when you use an inductor which has more than one layer of windings in a high ripple voltage circuit such as an SMPS, you will want to connect the lead from the outer layer toward the output cap which is more stable and shields the inductor better, and feed the pulsing voltage to the inner layer. This can have a significant effect on radiated electromagnetic emissions aka the radio interference your circuit causes and be the difference between passing and faililng compliance tests.

    Another thing is when you have more inductors close to one another, then there could be a difference between them being polarized the same way and the opposite way.
     
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  9. WBahn

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    Similarly, how you orient the inductors on the board influences the mutual coupling to other circuit elements.
     
  10. robsworld

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    That's good to know

    I did look in the datasheet but couldn't find nothing. Yes I'm sure its there but some of these data sheets don't use general terms so they can be very hard to understand when you know nothing about this stuff.

    Thankfully my boards are basic and seem to work ok.
     
  11. WBahn

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    Data sheets can definitely be hard to decipher -- and to some extent they always will be. You will learn what information is key to what you are doing and, right or wrong, will tend to gloss over much of the information that is presented (and sometimes this will bite you). But you will only gain this ability by reading the data sheets.

    One thing to keep in mind is what the likely implications are of information that is nowhere to be found in the data sheet. In this case, if the inductor WERE polarized, you can be pretty sure that this information would be fairly prominently indicated in the data sheet, just like it is for polarized capacitors. This is not a sure thing and it does involve reading between the lines and making judicious assumptions and inferences, something that you only get better at with practice and experience (and mistakes).
     
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