I have a couple of things in mind and I would like a source for those BIG toroidal ferrite cores. I can deal with painting the wire and wrapping it because you don't need that many turns. Really I can strip some 10 guage or something, maybe even fatter.

This of course yields what the problem is _ I want like an ID of AT LEAST an inch, a thickness of ¼ inch or better which gives an OD of 1½". The height should be approximately ½ - ¾ inch.

J

On 8/14/2012 10:39 PM, wrote:
I have a couple of things in mind and I would like a source for those BIG toroidal ferrite cores. I can deal with painting the wire and wrapping it because you don't need that many turns. Really I can strip some 10 guage or something, maybe even fatter.

This of course yields what the problem is _ I want like an ID of AT LEAST an inch, a thickness of ¼ inch or better which gives an OD of 1½". The height should be approximately ½ - ¾ inch.

J
It's not nearly that simple.
Toroids come in a wide range of permeability, saturation characteristics
and frequency ranges.
Here's a place to start
https://www.amidoncorp.com/

On Tue, 14 Aug 2012 22:39:35 -0700 (PDT), wrote:

I have a couple of things in mind and I would like a source for those BIG toroidal ferrite cores. I can deal with painting the wire and wrapping it because you don't need that many turns. Really I can strip some 10 guage or something, maybe even fatter.

This of course yields what the problem is _ I want like an ID of AT LEAST an inch, a thickness of ¼ inch or better which gives an OD of 1½". The height should be approximately ½ - ¾ inch.

J
Make sure that what you need is ferrite material. Ferrite toroids,
ungapped, have pretty limited use - in pulse transformers, common-mode
chokes, other EMC or damping functions and some saturable circuits.

Ferrite has more applications with other core shapes, where a gap is
more easily permitted.

For most power applications, you'll need a gap of some sort, or
another type of composite material that provides this characteristic
in a physically cut or distributed form - iron dust, MPP/sendust or
others. The descriptions of the latter can be found on Magnetic Inc,
Micrometals and other websites.

The odd iron dust toroidal core size shows up on E-Bay regularly, in
non-auction type sales. Core material can be identified in the part's
type number, and sometimes in the body colour code. Ferrites as well.

What are you building?

RL

Thje DC to DC convertor must be extremely high current because I want it to run off batteries. It has to kick the voltage up.

The reason I need my own desgn it because using high speed switching devices, I intend to eliminate the rectifiers and filter caps. I intend to use the high frequency AC directly.

I really should not say anymore right now. If I find what I need, get one going and file for a provisional patent, I will tell you all about it. I KNOW it can be used for industial applications already, but I want to to to use for another purpose. That is something I will not reveal until I at least have the provisional. It might not be enforcable, but it sure as hell proves prior art. At that point nobody can keep ME from marketing it.

(you should see what drug companies do, and Monsanto, they use patent laws in ways that would blow you mind)

J

On 8/15/2012 8:59 PM, wrote:
Thje DC to DC convertor must be extremely high current because I want it to run off batteries. It has to kick the voltage up.

The reason I need my own desgn it because using high speed switching devices, I intend to eliminate the rectifiers and filter caps. I intend to use the high frequency AC directly.

I really should not say anymore right now. If I find what I need, get one going and file for a provisional patent, I will tell you all about it. I KNOW it can be used for industrial applications already, but I want to to to use for another purpose. That is something I will not reveal until I at least have the provisional. It might not be enforcable, but it sure as hell proves prior art. At that point nobody can keep ME from marketing it.

(you should see what drug companies do, and Monsanto, they use patent laws in ways that would blow you mind)

J


Ok, so,
What is your input voltage?
What is your output voltage?
What current do you need on the output?
What frequency do you want the AC?

Answer those and we will have a better
handle on how to pick your core.

Mikek

Have you tried RS Components or Farnell?

I need to be around 60 - 100 Khz. There will be no active feeback loop, no regulation just brute force. Primary impedance will be so low that any spikes in the load will be immediately reflected to the source. It will run at resonance.

Square or sine, or something within reason at a constant frequency, able to deliver say 200 V P-P at eight amps or so.

Actually 75 Khz would probably be optimum.

J

On Sat, 18 Aug 2012 01:23:15 -0700 (PDT), wrote:

I need to be around 60 - 100 Khz. There will be no active feeback loop, no regulation just brute force. Primary impedance will be so low that any spikes in the load will be immediately reflected to the source. It will run at resonance.

Square or sine, or something within reason at a constant frequency, able to deliver say 200 V P-P at eight amps or so.

Actually 75 Khz would probably be optimum.

J

In order to run resonant, you'll need some kind of control to sync the
driver to the power transfer frequency. Self-oscillators tend to be
supply volage dependent, and the resonant frequency of the power
components will drift, all by themselves, with temperature.

Resonant converters tend to run intentionally above or below
resonance, FMing into the resonance to increase/regulate power.
Ungapped ferrite is unsuited to this application. Pick a ferrite core
shape that allows for introduction of a gap, or use a powdered core
material of suitable mix permeability and loss density for the
application.

You have to determine what you need, before you can go looking for it.

RL