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

[0c]

Should we not try to bias ferrite with external magnets as TK, Ossie, etc. have already shown (to raise permeability) rather than switch to a material like 1010?  Or is the total power to saturate (say to ~95%) the steel vs. ferrite from max permeability less?

That will improve the situation by driving the core partially into saturation, BUT it does so by rotating the domains 90 degrees from where the coil wil rotate them, so it is not the best way to go about it. And if you overdo it, you can actually make the situation worse. The core will be magnetized diametrically and the opposite side will act like an attractive magnet, giving you more attractive force between core and magnet than you would ordinarily have when the coil is off, and may have additional cost or reduced effectiveness when powered. Downside is, then you need more energy to the coils to overcome that additional attraction after the magnet passes dead center. It's a delicate balance to get it right.

If you can bias the toroid circumferentially, and apply current with proper assisting polarity, this becomes less of a factor and the domains will already be rotated in the correct direction. The important consideration is to have the permeability significantly greater when the magnet approaches than when it is departing. The most critical time is near dead center.

You could experiment with a toroidal transformer to see what works best. Apply a bias current to the primary to bias the core, then see how much current it takes on the secondary to saturate the coil and get the desired response. This will vary according to the properties of the core materials.

The best core materials would have high permeability (better attraction), low Bsat and/or high remanence (easier to bias), and a steep permeability decline when approaching saturation (less energy required for maximum effect). I have found data for mumetal which indicates it should be a good material for this purpose. There may be better materials.

Permendur looks like it might be good, has high permeability and remanence, but the downside is high Bsat. I haven't been able to locate a permeability curve for it yet, but if it's steep enough when saturated, it might compensate for the high Bsat.

[gravityblock]

I did a quick test in changing the polarity by reversing the negative and positive connections with dual magnets being like poles.  The direction of rotation changed also, which is not the same results as the test in the Steorn Demo.  This may be due to over-saturating the core and the magnets are being repelled instead of allowing it to pass by.  I need to lower my input energy I think.  I will put this on my list for tests to do with the dual magnets having opposite poles and testing both vertical and horizontal positions and with less input energy.  If the direction of rotation is the same with opposite poles after reversing the polarity, then Steorn's demo is using opposite poles.  If this is the case, then I must be overlooking something.  I will still say like poles is more efficient until I'm convinced otherwise.

I think OC is on the right path in finding the best core material.


GB

[0c]

I look at permeability as being 100% attraction and 0% saturation.  The permeability is just the inverse of saturation.  When the core is 100% saturated, then it will have 0% attraction.  When it is 0% saturated then it will be 100% attractive.

Not true, at least for some materials. Here's the permeability curve for mumetal:
http://www.magnetica.fr/repository/Fig26.gif

Notice that permeability when 0% saturated is only about 30,000 but it reaches its peak of almost 100,000 when partially saturated. If you can bias the core to the permeability peak without using any external power, you will have stronger attraction when the coil is unpowered and will require less power to drive the core into saturation.

[Magluvin]

Well look at OC go over here!  =]   
Hows it going OC?

Will we see any battery operated toys on yer bench any time soon? ;]

Magluvin

[0c]

Sorry, but I believe the rotor magnets must be opposite polarities and that the toroid coil must also be standing upright as in the three operating Orbo (I wonder if Orbo is also plural) to be OU.

It doesn't matter much WRT to saturation. It does matter WRT coil orientation. The way Steorn has their coils oriented in the eOrbos on display would require the magnet pairs to have the same polarity.