Re: Ferrite chokes & saturation - why toroids?
From: Malcolm Watts[SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent: Wednesday, November 26, 1997 1:24 AM
To: Tesla List
Subject: Re: Ferrite chokes & saturation - why toroids?
> From: Adam[SMTP:absmith-at-tiac-dot-net]
> Sent: Tuesday, November 25, 1997 10:02 AM
> To: Tesla List
> Subject: Re: Ferrite chokes & saturation - why toroids?
> I guess the toroid is so popular then because it is a common type of
> closed-core form (flux contained) that is readily available. Rods and
> slugs are great for making chokes for many applications, but I suspect
> that if these open ended core forms get too close to the Tesla primary,
> you could be in for some seriously unwanted induction- esp. if the cores
> are lined up axially with the tesla coil! For those of use whose power
> supplies are housed just below the coil itself, closed core chokes are a
> must. This is what led me to the double "U" cores from my flyback
> xfrmrs, though I suspect mine saturate at my current power levels.
I run chokes on ferrite rods right next to my primary. The primary on
that particular coil is a helix. I obviously don't stand the chokes
> That leads me to another question- If I cannot find larger "U" core forms
> than the flyback material (which I have in abundance) to build higher
> current chokes, can I simply wind four (or more) identical chokes and put
> them in series-parallel to increase power handling while maintaining the
> value (10 mH)? This seems like a valid approach, and should also better
> distribute the voltage across the chokes in series.
That sounds like an awful lot of trouble. You can heavily gap a core
but then you are approaching air permeability. My next chokes are
going to be air cored. I am going to wind them on old solder bobbins.
I will put de-Q'ing resistors externally and make sure the heating in
the chokes themselves is kept to a minimum. But then again, I am just
about moving away from chokes altogether, at least for neons.