Re: Mike Marcum Ferrite Cores

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: mecortner@xxxxxxxxxx 

>Just about anything including signal grade ferrites (Philips 3Hx,
>even 4Ex series) at those frequencies. The grain size is easily
small
>enough to obviate eddy currents. Hysteresis losses can be reduced by
>gapping the material if they are a problem. If you have some
ferrites
>on hand and know the grades, you can try and obtain data from the
>manufacturers or simply "Googling" them. Low hysteresis losses are
>signalled by a small enclosed area in the B-H curve. At low
>frequencies AND high signal amplitudes you are going to need high
>inductances to minimize the risk of core saturation which, if the
>core is gapped as well, implies large core size. A definite design
is
>going to depend heavily on design requirements and there is not
>enough data given to go on (yet).

>Malcolm


Thanks for responding Malcolm, actually all My ferrites
are just flyback type or SMPS cores from randomly junked
equipment. Enough material to make a real small generator
core, sort of a toy, but I don't think I could extrapolate
that to a larger version. I was hoping to find a inexpensive
part number from a distributor for the scale mockup, as
always the bugs are cheaper/easier to fix when things are
a bit smaller. Having said that, about all the material I
need now is a quart jar full of the powder.

I do understand the B-H curve but on this type of gen there
are no magnetic reversals to deal with. The material only
has to let go of the residual magnetism before the next pulse.
However the core saturation could be an issue? I guess I should
describe the thing, it's one of Tesla's own patents, a varying
DC sine output generator. It uses a unique coil geometry that
is 90 degrees to the magnet face with the back side shielded
by the core, this removes the magnetic drag even when it's
under load. which is the opposite of normal generators.
A friend has a book with the patent number in it, I'll get
it tomorrow and post so you can see what I'm talking about.

The magnets I'm using are grade 38 (38 mega-gauss) neo's,
3/4" dia X 1/8" thick, the core cross section will be
3/4" X 3/4". The problem here is the coil generates it's own
magnetic field when loaded, and that will add to the magnet's
field, this all flows through the 3/4" X 3/4" ferrite core.
How much gauss will go through a core cross section this size
before saturating?

---- Matt Cortner ----