Array of PMs on pole piece to= large PM?
Array of PMs on pole piece to= large PM?
(OP)
Is it possible to attach several permanent magnets to one side of piece of iron or other magnetically conductive material to get a highly uniform mag. field on the other side?





RE: Array of PMs on pole piece to= large PM?
The only way I know of obtaining a fairly uniform (=vector B constant in direction and value over a finite space) is the classical use of magnets: creating a gap in a horseshoe (=loop) configuration.
prex
http://www.xcalcs.com
Online tools for structural design
RE: Array of PMs on pole piece to= large PM?
-Todd619
RE: Array of PMs on pole piece to= large PM?
RE: Array of PMs on pole piece to= large PM?
RE: Array of PMs on pole piece to= large PM?
RE: Array of PMs on pole piece to= large PM?
RE magnets as large as 100x100x25 (and possibly more) can be fabricated, and they can be used in arrays of different types. No problem if you put them in series (one on top of the other), a little more difficult to put them side by side (with the same field orientation), as they repel themselves (though not with a very high force).
You can create a fairly uniform field of some 0.5 T in a gap of 100x100x15 mm by using two magnets as above (or more smaller ones) and an iron to close the circuit (and to resist the attraction of many kN): is this close to what you have in mind?
prex
http://www.xcalcs.com
Online tools for structural design
RE: Array of PMs on pole piece to= large PM?
To Hacksaw; I was hoping to just use a tunable RF source and amplify it to the required power with off the shelf budget minded equipment, I'm not sure what an xtal controlled exciter is, but I'll look it up when I get a chance.
RE: Array of PMs on pole piece to= large PM?
One catch. The best adhesives are epoxies, and they require heated cure cycles. You will get some demagnetization at cure temp. How much depends on what PM material you are using and how hot you work.
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Corrosion never sleeps, but it can be managed.
http://www.trenttube.com/Trent/tech_form.htm
RE: Array of PMs on pole piece to= large PM?
RE: Array of PMs on pole piece to= large PM?
These RE magnets if they are not coated seem to have a surface that would lend to very good bonding, anyone know what kind of tensile strength I could expect on the bond?
RE: Array of PMs on pole piece to= large PM?
Square or rect. is better so that you don't have gaps. They are a real bear to put together since they are magnetized. You need good clamps and fixtures because the repulsive forces are huge.
NeFe is nice because of the high B, you can get a lot of field. The demag that you get on slight heating isn't a permanent strucural change. But you would need to remagnetize in order to recover it. Mag'ing large assemblies is very tricky.
For high temp products (Alnico, and both 1:5 and 2:17 SmCo) we used ScotchWeld 2214. This is a 'B' staged epoxy with a fairly high cure temp (350F) and great strength. The epoxy and the bonds were stronger than the magnets. For working with NeFe we used a two part epoxy so that we could use low cure temp.
I would glue the magnets to a plate, and then to the pole pieces. The multiple bondlines don't help your magnetic field, but in these materials the impact is small.
How large of a magnet are you looking to build? I can look and see what I have around.
= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.
http://www.trenttube.com/Trent/tech_form.htm
RE: Array of PMs on pole piece to= large PM?
Also I'm thinking I'd like to bond them to a steel backing plate, Sreid said that that might smooth out the flux further and it would have the added advantages of being very strong and workable with a frame work to hold the two assemblies apart at a small distance and would also shield the field from everything on the other side. can a good bond be formed to steel with epoxy? I've seen transformer cores bonded in this way.