1.5T magnet 4

[magnetonico]

Hello:
I am considering to build a 1.5T magnet for my lab but, I would like to avoid dealing with a power supply & wiring considerations. I found very interesting the discussions posted on threads 340-132216 and 133735. However, I wonder which are the reasons for not using magnetic circuits based on permanent magnets (rare earths, alnico, etc.). The question I have is how difficult and/or expensive may be to reach 1.5T in a 25mm gap using this approach instead the classical electromagnet design. I will be really thankful in getting some feedback on this. Thank you very much in advance for any comment!.

 

[IRstuff]

I was thinking that most of sreid's posting was urban legend, but it's mostly true:

http://www.webmm.ahrq.gov/case.aspx?caseID=4

http://www.fda.gov/cdrh/ode/primerf6.html

The exception is that the articles list forklift tines, but not an entire forklift.

TTFN

 

[sreid]

Elecrtomagnets and permanent magnets both have their place. But Neo magnets with their high energy products, small volumes and now low cost (most Neo magnets are now made in China)allows them to be used in applications that were not considered before. For example Hard Disk Drive motors and Cell Phone Loud Speakers.

Everyone who works with RE magnets will probably get pinched once (me!) before they get religion. And I once demagnetized all my Credit Cards. And I magenized a Milling Machine Quill which really ticked off the Machine Shop Foreman since the edge finder "Wiggler" indicated an edge about 0.050 early from magnetic attraction.

Large RE arrays will become common in certain applications. Halbach arrays are already used in particle accelerators and will likely be be used in Maglev's.

http://www.matchrockets.com/ether/halbach.html

 

[magnetonico]

Yes. In fact, is dangerous. Special tools may be prepared in order to mount a PM system without doing mesh. But with extreme care I hope it can be handled. I should say that each approach has an intrinsic point. In order to answer to skogsgurra, the DC power supply adds cost to the system while the complexity would depend on the needed stability of the field & power supply. Of course, if no high stability requirements are needed, this point goes to a second plane.

 

[mwemag]

A relatively small scale PM with 5T force in a 0.25 mm airgap without need for electrical supply or cooling is described in the following link. However the force will be considerably smaller in a 25 mm airgap and the device may be quite complicated to do it yourself.

http://mag-net.ee.umist.ac.uk/reports/P14/p14_2.html

 

[magnetonico]

Thank you very much Mwemag. It looks very interesting, I will have a look on that with more care as soon as possible.