Re: Ferrite types and chokes
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
> 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.