Inductors in parallel

Discussion in 'General Electronics Chat' started by wes, Dec 25, 2010.

  1. wes

    Thread Starter Active Member

    Aug 24, 2007
    242
    2
    Hi, I was just looking up inductors and parallel and it go me thinking. I know that inductors in parallel decrease the inductance of the circuit and serial adds.

    I was just wondering though that even though the circuit inductance is lower in parallel and so the Rise time would be faster, each individual inductors rise time will still not be affected right?

    I figure this is correct just because the inductors themselves have not changed.


    If they are not and their individual rise times are actually shortened, then please explain.

    Oh forgot. I said rise times because since the inductance determines the rise times, among other things, changing the inductance up or down would change how quickly it can reach steady state.
     
    Last edited: Dec 25, 2010
  2. edgetrigger

    Member

    Dec 19, 2010
    133
    19
    I hope you have got it wrong. It wont be faster when you connect inductance in paralle. L equivalent will come down, so does the equivalent resistance. So time constant remains the same. L/R will remain the same. The rise time cannot shorten.

    You could consider this case :

    L = 1 henry and R = 1 ohm. L/R = 1 sec

    L1 =1, L2 = 1, L3 =1 ; in henrys
    R1= 1, R2 =1 R3 =1 ; in ohms

    Leq = 0.333 henrys
    Req = 0.333 ohms

    Leq/Req = 1 sec again.
     
  3. wes

    Thread Starter Active Member

    Aug 24, 2007
    242
    2
    ok thanks. just wanted to make sure
     
  4. wes

    Thread Starter Active Member

    Aug 24, 2007
    242
    2
    also just real quick.

    Inductors perpendicular to each other should not induct right?

    like this

    ----------- L1

    |
    | L2
    |
     
  5. edgetrigger

    Member

    Dec 19, 2010
    133
    19
    yes you are right. Theoretically mutual inductance will be zero. But not true for R.F. Circuits. The electonic hanchos call it stray inductance and what not.
    Not to worry for a low and mid frequencies.
     
  6. wes

    Thread Starter Active Member

    Aug 24, 2007
    242
    2
    ok, I just tried in a program called Vizimag and according to it, they still induct even a little. it said it was like 20% efficient. I have heard this software is not that great but it is easy and fun to use, just not that accurate.

    of course my Coils were 1 inch apart and about 4 inch in diatmeter, lol, so I would expect some inductance.


    http://vizimag.com/
     
  7. edgetrigger

    Member

    Dec 19, 2010
    133
    19
    minimal mutual inductance should be there as there would some flux linkage but getting 20% is doubtful. It cannot i suppose. 1 inch of air gap is too much of a reluctance in between. I have not dealt with high frequency model of this.

    If you are having an interference problem then the best thing is to shield it by any metal or preferably by mu metal.
     
  8. wes

    Thread Starter Active Member

    Aug 24, 2007
    242
    2
    ok, thanks, I guess it is just the program, I will contact the company or person and ask if maybe I am just doing something wrong. ( not using the program correctly, lol)

    I thought there was something wrong when it said that their would be inductance and quite high too, lol, when perpendicular to each other
     
  9. timrobbins

    Active Member

    Aug 29, 2009
    318
    16
    It can also depend on the angle that the inductor wire makes wrt the other inductor's field. A helical single layer winding can have a wire angle significantly away from physical 90 degrees. Likewise, if you have a relatively short winding length inductor then the angle of the field is only parallel to the physical direction of the inductor for one external 'point' (circular locus).

    Ciao, Tim
     
  10. wes

    Thread Starter Active Member

    Aug 24, 2007
    242
    2
    That makes sense, even though the coil itself is perpendicular, the way the wire's are wound may be less then 90 degrees. So since the wire's are not exactly 90 degrees, they will have mutual inductance.
     
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