Re: Ferrite chokes & saturation - why toroids?

To: "'Tesla List'" <tesla-at-poodle.pupman-dot-com>
Subject: Re: Ferrite chokes & saturation - why toroids?
From: Tesla List <tesla-at-stic-dot-net>
Date: Mon, 24 Nov 1997 18:54:17 -0600
Approved: tesla-at-stic-dot-net

From: 	Adam[SMTP:absmith-at-tiac-dot-net]
Sent: 	Monday, November 24, 1997 10:26 AM
To: 	Tesla List
Subject: 	Re: Ferrite chokes & saturation - why toroids?

>Depends on the losses in the grade of ferrite you are using, wire 
>size and operating flux density. For example, a high permeability core 
>with a few turns might look great at a few mA on an inductance meter
>but be a total loser at a more substantial power level. An iron 
>powder core of he same size might look pretty lousy with the amount 
>of wire needed to get the same L but would fare better with real 
>power applied.
>
>Malcolm

I noticed you mentioned that an iron powder toroid would need many turns 
of wire for the proper inductance, due to low permeability of the core.  
My question is: isn't it a real pain to wind wire through a toroid?  I 
have been using ferrite "U" cores taken from old B&W TV transformers, 
winding each half separately, and then Krazy gluing them together (with 
spacers).  Also, ferrite is usually gapped between the halves as a 
measure against flux saturation at DC and very low (60Hz?) frequencies- 
kind of impossible to do with a toroid (without breaking it in half :-)

The "U" core shape definitely seems easier to wind- is iron power 
available in shapes other than toroid? Is there a good reason for using 
the toroid?

-Adam

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