Re: Ferrite types and chokes

To: "'Tesla List'" <tesla-at-poodle.pupman-dot-com>
Subject: Re: Ferrite types and chokes
From: Tesla List <tesla-at-stic-dot-net>
Date: Mon, 17 Nov 1997 23:37:02 -0600
Approved: tesla-at-stic-dot-net


From: 	Malcolm Watts[SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent: 	Monday, November 17, 1997 2:06 PM
To: 	Tesla List
Subject: 	Re: Ferrite types and chokes

Hi Adam,
 
> From:   Adam[SMTP:absmith-at-tiac-dot-net]
> Sent:   Sunday, November 16, 1997 12:13 PM
> To:     Tesla List
> Subject:    Re: Ferrite types and chokes
> 
> 
> >>Also, does anyone know the difference between the different types/grades
> >>of ferrites?   I am most interest in the frequency ranges and
> >>*permeability* values.  Does the tesla list have a nice table for this,
> >>as it does for dielectric constants?
> >
> >Amidon sells ferrite toroids, rods, e-cores, etc.  They sell in small
> >quantities, no minimum order, and have a very good technical guide on the
> >web at http://www.bytemark-dot-com/amidon/index.htm
> 
> I visited here, and from what I gathered it seems that the super high 
> permeability W and H materials are most well suited to attentuating 
> frequencies in the operating range of small to medium-large tesla coils 
> (under 1MHz).  For W material, initial permeability is given as 10000, 
> with a maximum of 20,000.  The only thing that seems potentially 
> undesireable about these materials is that they both have low curie temps 
> (125 and 120 deg.C) so that it would be very important that these chokes 
> not get hot.
> 
> Any thoughts?  What are people using now for RF choke materials?

With initial permeabilities like that they will saturate with very 
little A-T applied. Iron powder is definitely the material of choice
for toroidal cores for our apps.

Malcolm