I sent one post which hasn't shown up yet... Perhaps its awaiting Bills
scrutiny before allowing it
thru. It had a JPEG attachment of how the inductance of the toroidal coil
changes by a factor of 5
as the rotor magnets approach and move past the coil...
More quotes from the Steorn Forum to show that Sean is revealing a considerable
amount of details,
although not all at this time... Can't blame him.
-Mark
Here is the weblink...
http://www.steorn.com/forum/comments.php?DiscussionID=62495&page=1
and here is how Sean opens the discussion...
---------
Folks,
Please post any rational questions/concerns/comments on the second experiment
in this thread. We
hope that we were able to address several of the concerns expressed about the
first experiment
during the second one. Again we would like to keep this process as observer led
as possible.
Please keep the posts on subject, polite and focused.
Thanks,
Sean
[ME: And some specific quotes below...]
---------------------
Steorn:
There is no back emf in any of the coils in the experiment shown - it is not a
case of one coils
Back EMF cancelling out the other.
----------------------
overconfident:
What core materials are you using?
Steorn:
Just a soft magnetic material - I will not go into the details - sorry.
----------------------
overconfident:
Is there any hard magnetic bias in the toroidal cores?
Steorn:
No
----------------------
Steorn:
The magnetic arragement on the rotor is the same in both cases, an N pole above
an S pole (or the
other way around). The coils in the pulse motor (like the coils on the Orbo
motor) are both facing
up.
----------------------
Steorn:
There is no back EMF in any of the coils due to the motion of the rotor. All
coils suffer CEMF
during the inductive rise and collapse of the field.
----------------------
overconfident:
Does your "secret" core material demonstrate a significant Wiegand effect?
Sean: No
----------------------
Steorn:
... but as I keep saying this stuff does take a huge amount of precision
positioning to get right.
----------------------
They use counter EMF and back EMF... Many were confused by that, including me.
Wikipedia has this
explanation, however, I don't know if Sean is using these definitions...
WIKIPEDIA:
The counter-electromotive force (abbreviated counter emf, or CEMF ) is the
voltage, or electromotive
force, that pushes against the current which induces it. CEMF is caused by a
changing
electromagnetic field. It is represented by Lenz's Law of electromagnetism.
Back electromotive force
is a voltage that occurs in electric motors where there is relative motion
between the armature of
the motor and the external magnetic field. One practical application is to use
this phenomenon to
indirectly measure motor speed and position. Counter emf is a voltage developed
in an inductor
network by a pulsating current or an alternating current. The voltage's
polarity is at every moment
the reverse of the input voltage.
[links to references deleted]
---------------
[ME: Here is one observers explanation that is a good start at understanding
what's happening...]
1) First stage
Rotor magnets are approaching the toroidal coil. They are simply being
attracted to the core. Coil's
circuit is open. As the magnets' "coupled" flux goes through part of the
toroid's core this induces
EMF in the coil - an electric potential difference across two open-circuited
terminals. The current
doesn't flow so there is no Lenz interaction with the rotor.
2) Second stage
Magnets reach TDC. Magnets "coupled" flux goes through half of the toroid. Or
it's being divided by
two - part of the flux goes left side of the toroid and the other part goes
right side of the
toroid. How it is in fact doesn't really matter.
As the magnets reach TDC, we close the electric circuit and fire up the current
to saturate the
core. As the core is partially saturated by magnet's flux we don't really need
much current (this is
the main and very important difference with JLN setup).
Why don't we see any Back EMF here? Simply because magnet's "coupled" flux will
always choose the
simplest way to go - the way it finds no magnetic resistance. So magnet's
"coupled" flux lines will
always align here with the coil's magnetic flux lines. So as these flux lines
do not "fight" with
each other - we simply have no Lenz Law interaction here.
3) Third stage
As the magnets go past the toroid, their flux lines still align with the coil's
flux lines but the
aid they provide in saturating the core is getting weaker with the distance
from the toroid.
However, the current input (to keep the saturation) stays constant at some
point (in fact very
quickly) because of the core's material properties. Remember the graph
"Amplitude Permeability vs.
Flux Density" for Metglas? What you find in this graph is: The higher the flux
density, the lower
the permeability. However for metglas the permeability stays constant between 0
- 0.47T. As the
permeability is getting steady and constant, the current needed to keep the
core saturated is also
getting constant. This is exactly what you see on the scopes. As the magnets
move on, there is still
no Back EMF because there is still no "negative" interaction.
At some point we open the coils circuit and the process repeats.
-----------------------
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