Re: Mike Marcum Ferrite Cores

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Malcolm Watts" <m.j.watts@xxxxxxxxxxxx>

Hi Matt,

On 23 Oct 2005, at 18:44, Tesla list wrote:

> Original poster: mecortner@xxxxxxxxxx
>
>  >For a single-ended forward converter which delivers power to the
>  >load during switch conduction time, the core only gets magnetized in
>  >one direction. Since you cannnot deliver power for 100% of a cycle
>  >with this type of converter (the core has to recover - fall back to
>  >near zero magnetism while the switch is off), some of the time is
>  >effectively wasted.
>
> Hi Malcolm
>
> A forward converter is about the closest thing to
> what I'm doing and I bet the same rules will
> apply to. I'll do a sketch of this thing and
7> post it in a few days, hopefully.
>
>
>  >The main dependency
>  >for a given core involves copper losses - i.e. the size of the
>  >winding window limits the amount of copper you can fit in there and
>  >the minimum inductances you can get away with - as in fewer turns -
>  >determines the maximum wire gauge.
>
> Good point, and I've been pondering this too.
> Just how big should the holes in the core be?
> But if I mess this up and cast them too small
> I can always drill them out a little.

The way it works is that the winding window shape is more-or-less
optimized to obtain maximum coupling between each winding and the
windings and the core (which in turn minimizes leakage inductance for
well designed windings). Additionally, the summed area of the core
legs = the area of the centre-pole which minimizes flux leakage.
I don't understand what you mean by drilling the holes out. Which
holes?

Malcolm