STEORN DEMO LIVE & STREAM in Dublin, December 15th, 10 AM

[teslaalset]

A very basic question to you knowledgeable people around here:
In Steorn's latest videos they showed some details of the current measurements, like below picture taken from one of these videos (the yellow trace)

Now, according to theory, if you switch on a coil, the current flow is increasing very rapidly from the start and then saturates (like the black curve in the graph below)
Steorns current curve shows differently, indicated by the blue dashed curve in the same graph below

Why is that?

[exnihiloest]

Hi Gang,

Viscous pulse in a MetGlass core.  Non canceling mode  first.

http://www.youtube.com/watch?v=qu21E9s29ZQ

Respectfully
Ben

Very interesting and informative test, Ben.

When the magnet is approaching, we see a first positive pulse. At a particular level threshold, the signal goes back to zero and remains at zero, and after a certain delay, there is a negative pulse when the magnet moves away.

Imho it is not a question of magnetic viscosity. The first positive pulse is caused by the variation of magnetic flux from the magnet through the coil (classical induction law). The increasing flux gradually saturates the toroid core. The saturation of the core reduces the permeability, producing an opposing flux variation through the coil. We have two antagonist effects.
At a particular threshold, the variation of flux because of permeability change is equal to that one from the approaching magnet. The variation of flux is nullified. The signal abruptly falls to zero. It does not become negative, because the flux change because of permeability cannot exceed that one from the moving magnet: we have like a servomechanism, with feedback between magnet flux and permeability flux changes. This balance is shown by the flat step.
At some position, the flux change because of increasing permeability can no longer compensate the decreasing flux change from the magnet moving away, thus we have the negative pulse (classical induction law).

The flat step is the more interesting. It is the reason of constant values of U and I of the pulse powering the Steorn motor.

[gravityblock]

Yes I've also noticed that but looking at the hysteresis loop makes me think that they've just simply made a mistake in the table. All in all Bsat for Finemet is 1.23T.

The word maximum has no meaning to you?  It could very well be a mistake as you suggested, but this "maximum" flux density suggests it is not a mistake in the table.  Also, the table shows both the saturation flux density and the saturation induction (maximum flux density) at 20 degrees for the Finemet.    The Saturation flux density is 0.57T and the saturation induction at 20 degrees is 1.23T.  Why would they list both in the table if they were the same?  They also don't bother to list the saturation induction numbers with the Meglas, why not?  I don't think it's a mistake, those two numbers appear to have different meanings and that's why they're both listed in the table.  The saturation induction is probably a unique property of the Finemet cores as compared to the Metglas cores.

This could be what is responsible for the energy gain in inductance due to the Aharonovâ€"Bohm effect.  A material may have an Aharonovâ€"Bohm effect, but if the core can't hold the additional energy being pulled into it, then it won't have an energy gain in inductance.  There will only be an energy gain in inductance if the core can hold this additional energy due to the Aharonovâ€"Bohm effect or other unknown effects that is pulling this additional energy into the core material.  If the saturation induction is higher than the bsat, then the core can hold additional energy that is being pulled into it, thus an energy gain in inductance.  Other than this, the Finemet and Metglas cores are almost identical in properties.  There must be something different between the two cores, and I think the main difference is the saturation inductance.

We need a little diversification.  Don't put all of our eggs in the same basket.  I guess we need to find out if it's a mistake or not, and if it's not a mistake, then what are the advantages and disadvantages with this material.  You do bring up a good point with the hysteresis loop though.  Fascinating stuff.

[Edit:]  There is a saturation point where the core starts to lose attractiveness (around 0.45T), a saturation point where the core is no longer attractive (0.57T, Bsat), and a saturation point where additional flux can no longer be held within the core (1.23T, Saturation Induction).  This is how I'm looking at it.

In the Finemet, 1.23T / 0.57T = 2.15 and 1.23T / 0.45T = 2.73.  These numbers with the Finemet cores are close to the Cop > 2 claims by Steorn. 

In the Metglas, 0.57T(Bsat) / 0.57T (assuming the saturation induction is the same as the Bsat) = 1.0 minus electrical losses, air friction, friction in the bearings, etc. would put it below unity with the Metglas cores, or at unity/slightly above if the saturation induction is a little higher than 0.57, or if we calculate it with 0.45T with the Metglas.  I realize this may not be the correct way to figure this up and could be called pseudoscience, but the results are interesting nonetheless.  Why isn't the Finemet cores being discussed as a possible core material?  IMO, the Finemet has some interesting potential and shouldn't be ignored.


GB

[markzpeiverson]

A very basic question to you knowledgeable people around here:
In Steorn's latest videos they showed some details of the current measurements, like below picture taken from one of these videos (the yellow trace)

Now, according to theory, if you switch on a coil, the current flow is increasing very rapidly from the start and then saturates (like the black curve in the graph below)
Steorns current curve shows differently, indicated by the blue dashed curve in the same graph below

Why is that?

I thought Sean explained that... I remember him referring to that noisy, gently sloping up region before the vertical increase in current.  Does it have to do with the turn on time of the switching device?

What's the time-scale/division on that pic?

-Mark

[teslaalset]

I thought Sean explained that... I remember him referring to that noisy, gently sloping up region before the vertical increase in current.  Does it have to do with the turn on time of the switching device?

What's the time-scale/division on that pic?

-Mark

Sean mentioned that this is related to the change in permeability.
Change in permeability means change in induction value.
It still remains an induction. The curve doesn't indicate that.

Time scale, vertical, is 10 mA per division.