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

[PaulLowrance]

One thing is for certain, and that if the magnet is too close to the core, then it requires too much current.

Why is that The core should saturate more so the current needed to fully saturate it should be less.

Because the magnet does not saturate the core circumferentially. Only the coil can do that. Saturation is not saturation. The Metglas MAGAMP core wants to be saturated circumferentially. The magnet does not want that.

[0c]

1. Saturate the core at TDC
2. Leave the saturation point at some point where it's no longer needed.
3. We've got some remaining field in the core (as high as the remanence is).
4. Next set of magnets is approaching the toroid.
5. As we were left with some level of magnetisation (due to remanence) the approaching magnets will add some more magnetisation to the core. This will simply lead the saturation way too quickly (before the magnets reach TDC) and so all in all will reduce the torque

Permeability reaches its highest when the flux density B is near the knee of the BH curve, not when B is at zero. A material with remanence at a B near max permeability will have higher permeability when the magnet is at a distance. As the magnet approaches, the core will saturate further, permeability will drop until it is at its nonenergized minimum when the magnet is closest. When the coil is pulsed and held energized for the required duty cycle, the permeability will drop even lower.

The ideal condition would be for the permeability to be highest when the magnet is approaching, to remain near the top of the permeability curve until the magnet is very close. IOW, it should still not be completely saturated until the pulse is applied. So the saturation flux density should be higher than what can be provided by the magnet alone. The Metglas saturates too easily and can almost be completely saturated by the magnet alone.

Higher Bsat will also provide for greater attraction force and torque.

0c

[gravityblock]

@Syncro1 and all:

I decided to upload a video showing how the recording tape has magnetic attraction.  It even has enough magnetic attraction to catch a falling magnet, http://www.youtube.com/watch?v=sZhw0o_YzHg

GB

[PaulLowrance]

The Metglas saturates too easily and can almost be completely saturated by the magnet alone.

That's simply not how magnetic material works. The Metglas core only has high permeability for a closed loop magnetic field, which can only come from the coil. The effective permeability from an external field such as from a magnet on the Metlgas core is ~ 10 at most. Yes, that is correct, an effective permeability of ~ 10. That is not 10 thousand. That is not 10 million. Just 10. To be more specific, somewhere between 2 and 10.

Higher Bsat will also provide for greater attraction force and torque.

As stated too many times already. That extra force and torque comes at a heavy price. You can more force & torque by moving the magnet closer, but that's suicidal, which is why Steorn does not do that, because it requires too much current to fight the magnet-- P=I^2*R


Geez, doesn't anyone in this thread understand fundamental magnetic theory?     Again, this based on fundamental magnetic theory & a lot of experiments that I've seen countless times.

[0c]

That's simply not how magnetic material works. The Metglas core only has high permeability for a closed loop magnetic field, which can only come from the coil. The effective permeability from an external field such as from a magnet on the Metlgas core is ~ 10 at most. Yes, that is correct, an effective permeability of ~ 10. That is not 10 thousand. That is not 10 million. Just 10. To be more specific, somewhere between 2 and 10.

Do the inductance tests like Max did in:
http://www.youtube.com/watch?v=VYGSdUdONpw

or like Naudin did in:
http://www.youtube.com/watch?v=ww-F5MfWSGA

Note how much change there is in the inductance and ask yourself what else is changing to cause that inductance change?

As stated too many times already. That extra force and torque comes at a heavy price. You can more force & torque by moving the magnet closer, but that's suicidal, which is why Steorn does not do that, because it requires too much current to fight the magnet-- P=I^2*R

Maybe not as heavy a price as you might think, when you consider the remanence of square loop material will retain most of the magnetization. Yes, the distance between magnet and core may need to be adjusted. The objective is to spend as much time as possible on the saturation side of the permeability curve.

See the permeability curve here:
http://www.tpub.com/content/neets/14180/css/14180_137.htm

Paul, you seem to think everyone who doesn't agree with you is stupid or uneducated. Please take the time to perform some inductance testing with your cores, see just how much influence those magnets really have.