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Re: Choke winding question

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Saturation occurs at the same N*I for a given core shape and size, 
independent of gap*.

*Not quite independent due to fringing, but in the small-gap limit, this 
works.

Physically, this is because Ae is the same, and you can only pack so much 
flux density Bsat into the core.  Bsat (== Vs/mm^2) * Ae (== mm^2) == Vs 
(flux, integral V dt applied to the core).

The average (or effective) permeability that's best depends on a number of 
optimization factors, but it's in the 20-60 range.  The lower A_L cores in 
that selection will have this property.

As you note, lower mu_eff is higher energy (because the energy is stored in 
the air gap, which is larger), but harder to wind (takes more copper for the 
same losses).  (If we had superconductors, a very low mu_eff would be 
manageable, and we could do air-core inductors without worry.)

Tim

-- 
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
Website: http://seventransistorlabs.com


"Clive Arthur" <cliveta@nowaytoday.co.uk> wrote in message 
news:oabn87$5ag$1@dont-email.me...
>I was using a Ferroxcube calculator to work out some choke windings. These 
>have to be multiple RM12, about 5mH and 2.5A DC, so I was looking at the 
>maximum inductance before saturation for different cores.
>
> A 400nH core means 4 series cores each with 57 turns giving 1.3uH each.
> or 3 x 250nH cores with 89 turns, 2000uH each
> or 10 x 1000nH cores with 22 turns, 500uH each.
>
> The 400nH cores are probably best, 89 turns won't fit with reasonably 
> thick wire and 10 cores is painful.
>
> However - it seems that the /total/ number of turns is about constant. Is 
> that a rule of thumb, just normal or just lucky?
>
> Cheers
> -- 
> Clive 

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Choke winding question Clive Arthur <cliveta@nowaytoday.co.uk> - 2017-03-15 15:42 +0000
  Re: Choke winding question Winfield Hill <hill@rowland.harvard.edu> - 2017-03-15 09:48 -0700
    Re: Choke winding question Clive Arthur <cliveta@nowaytoday.co.uk> - 2017-03-15 17:03 +0000
  Re: Choke winding question John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-03-15 10:29 -0700
    Re: Choke winding question Winfield Hill <hill@rowland.harvard.edu> - 2017-03-15 11:37 -0700
    Re: Choke winding question Clive Arthur <cliveta@nowaytoday.co.uk> - 2017-03-15 22:02 +0000
      Re: Choke winding question Winfield Hill <hill@rowland.harvard.edu> - 2017-03-15 15:16 -0700
        Re: Choke winding question Clive Arthur <cliveta@nowaytoday.co.uk> - 2017-03-15 23:36 +0000
          Re: Choke winding question rickman <gnuarm@gmail.com> - 2017-03-15 21:41 -0400
            Re: Choke winding question Phil Allison <pallison49@gmail.com> - 2017-03-15 19:28 -0700
            Re: Choke winding question bill.sloman@ieee.org - 2017-03-15 20:12 -0700
              Re: Choke winding question rickman <gnuarm@gmail.com> - 2017-03-16 00:00 -0400
                Re: Choke winding question Clive Arthur <cliveta@nowaytoday.co.uk> - 2017-03-16 09:03 +0000
              Re: Choke winding question Winfield Hill <hill@rowland.harvard.edu> - 2017-03-16 05:56 -0700
                Re: Choke winding question bill.sloman@ieee.org - 2017-03-16 09:42 -0700
  Re: Choke winding question legg <legg@nospam.magma.ca> - 2017-03-15 19:23 -0400
  Re: Choke winding question "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-03-15 22:56 -0500
    Re: Choke winding question Phil Allison <pallison49@gmail.com> - 2017-03-15 22:30 -0700
      Re: Choke winding question "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-03-16 15:08 -0500

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