Ferrites, air-gaps, inductors

To: "'Tesla List'" <tesla-at-pupman-dot-com>
Subject: Ferrites, air-gaps, inductors
From: Tesla List <tesla-at-stic-dot-net>
Date: Mon, 16 Feb 1998 22:59:11 -0600
Approved: tesla-at-stic-dot-net


----------
From:  Bill the arcstarter [SMTP:arcstarter-at-hotmail-dot-com]
Sent:  Monday, February 16, 1998 10:14 AM
To:  tesla-at-pupman-dot-com
Subject:  Ferrites, air-gaps, inductors

It was written:
>> You should use the largest core you can find, this will allow you 
easy
>> winding and better insulation. A large core will be able to handle
>> higher flux densities before becoming saturated, this is important.
>> I do not think you need to go to such a high inductance, as ringing 
in
>> the choke may become a problem in its own right. As for the material 
a
>> power core material such as Philips 3C85 would be a good choice.
>
>I agree, but beware of using ungapped cores made of this material 
>unless the inductance is real high because the lack of airgap will 
>allow the cores to saturate easily. Magnetic material is capable of 
>storing very little energy. Most is stored in the airgap of gapped 
>inductors. A better choice for a core you don't want to stick a gap 
>in is a low permeability one as this will have a distributed airgap
>(well iron-powder cores do anyway). Of course, low permeability = low 
>inductance for a given number of turns so there is a horrible 
>tradeoff occurring. Frequency-wise, 3C85 is a good choice. 
>
>Malcolm

Over the weekend I fluoro'd a commercially-made rod choke, about 1/2 
inch in diameter by 5 inches long.  The inside was composed of five 
1-inch lengths of ferrite bar, with about a 1/16 inch gap between each 
rod.  Perhaps Malcolm's comments explain why this wasn't just one solid 
ferrite bar.

(Having access to an X-ray machine has it's advantages...)

This was the HF coupling transformer out of a TIG welding 
arc-stabilizer. It wouldn't have saturated under conditions of 200 
(60Hz) amps, ten turns of wire.  I'd like to make another one, which is 
why I asked about the ferrite rods the other day.

-Bill the arcstarter
Starting arcs in Cinci, OH


______________________________________________________
Get Your Private, Free Email at http://www.hotmail-dot-com