"Turn Off" a PM... Strategies

[MarkE]

The mechanical force is a function of the flux density and the perpendicular cross-section that the flux penetrates.  You get low force by:
Having low net flux density normal to the material or
Small area

There are lots of ways to get low flux density:  Low absolute field from one source.  Low net field from multiple sources (such as by cancellation), large reluctance gap, low permeability material (including due to saturation)

Small area is usually just from the feature sizes.  But it can also result from orientation.

[TechStuf]

There are lots of ways to get low flux density:  Low absolute field from one source.  Low net field from multiple sources (such as by cancellation), large reluctance gap, low permeability material (including due to saturation)

Certainly.  Yet, history is littered with so many failures down that road, as low flux densities produce no energy, while consuming energy to change their condition.  The energy required to change flux path direction while maintaining HIGH flux density has proven to be worthwhile in a number of impressive devices over the years.


Howard Johnson


Qin Gang


Stephen Kundel


To name just a few.

[lumen]

Since the thin sheet is centered between two circular magnets and is in a constant field, it takes no energy to rotate. When an external magnet is near and the exposure is limited to the very thin edge of the metal.

Though the idea is the attraction through the two large magnets. No attraction where there is no metal and attraction where there is metal. Where the attraction is greater than just the metal itself.

Still, keep in mind this is the simulator and it's only a concept at this point.

[dieter]

BUZZ!!!


WOW, STRANGE ARTEFACT !!! This could be my lucky day! Tho, yet to be verfied:


I took a paper and on that paper I had some graphite powder, maybe a tablespoon of it. I was shaking the paper gently, so the powder would spread somewhat.
Then I took a magnet pretty strong one from a huge 20 Mb Harddrive (when it comes to magnets from harddrives: the older the bigger the better, anyway).


I moved the magnet under the paper to see the diamagnetism when I made this amazing observation:


When I moved the magnet forward (away from me) and back, some graphite went always away from me!!! That means, when I was getting closer to that certain crumble from the distance, it was attracted, but ad soon as the magnet passed by, it was repelled, when I moved it the other way, its behaviour was reversed !!!!!!!! I even angled the paper, so the crumble had to travel upward, and it did!
Orientation in Space may play a role.
I don't have to explain you, that this would allow for a perpetual Spin! And some Nanotubes made of carbon may have extreme diamagnetism values.
I had to hold the magnet in a certain angle to the paper, maybe 45 degree, otherwise it wouldn't work.


Gotta verify this... So can you!

[dieter]

BTW. thanks for your replies. Lumen, this reminds me of my experiments with needles, in my amateur llingo called oversaturation.


Hope you don't mind, but ATM I have to study this graphite phenomen.