Joe,
One would think that but from every book I have on the subject (a good 20-30),
it's not because they still follow the grain of the steel either way. There was
some speculation about that when they were first designed, but I think actual
tests shown different. The power companies run these tests as they were
deciding which type to use. What causes the impedance to flow (reluctance) is
if the grain is oriented or not, the eddy currents, and core material. Even
though they look different, those extra sharp corners on an EI core compared to
a C-core don't even have any flux lines going through them as they follow a
radius at each corner. Same in the middle where the core is. They converge into
two radii at the core center leaving a "V" at the top and bottom of no flux
lines (when magnetized). The pattern looks like a C-core, even though its an EI
core. Now it may be some better than an EI core here, but I think they
determined the difference was not great enough to award anything
to it. The main thing is that stinking gap, which no matter how smooth you
make it, and how carefully you align it, still has more reluctance than a solid
core. An interleaved core is the closest thing you can get to a solid core,
solid meaning the flux path. The closest thing they have come up with was a
C-core the actually lapped down to about a 4 micron gap which did control
saturation somewhat without raising the reluctance too much. I would think
something lapped that smooth, you could see yourself in it. The only problem is
the manufacturing costs for something like that would be outrageous.
What my main thing is that the C-core will heat up more than a comparable EI
core which destroys its life. Not just because of the iron mass being smaller
but the gap raises it. Plus, as with any resistance, the hotter it gets, the
more reluctance you get, and the losses goes up. I explained some other types
they used at the reply to Rich where they tried to get around the air gap.
Running tests while both is cold don't hold much water, but running tests after
both have reached their maximum temp. under load will reveal all. See, I'm not
saying a C-core is not of any benefit, but that a M6 material is the same
material as Hipersil, and that an EI core simply runs cooler. Also, when
comparing the watts per pound loss curves between two comparable cores, the EI
core is just as good if not better. Hope this helps in my explanation.
Best,
Will
*********** REPLY SEPARATOR ***********
On 4/18/05 at 9:14 AM Joe Subich, K4IK wrote:
>>
>> On Apr 18, 2005, at 3:13 AM, G3rzp@aol.com wrote:
>>
>>
>> I vaguely remember somewhere the claim that because the C
>> cores are precision ground, the overall magnetic reluctrance
>> is less.
>>
>
>I'm only speculating but is it possible that the difference
>is the orientation of the core? Since the C-core is wound,
>the laminations are radial vs. a perpendicular orientation
>in the EI-core.
>
>It has been 30 years since I have any electromagnetics (and
>I haven't used it since <G>) but I believe the C-core's
>laminations are aligned parallel to the magnetic flux vs.
>perpendicular with an EI-core. It would seem that change
>would result in a lower magnetic reluctance as the flux is
>able to "flow" with (in) the laminations rather across them.
>
>73,
>
> ... Joe, K4IK
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