speedmd
10 MW
These guys are doing it as you pictured but looks like they added a coil.
Building a triple stator axial flux motor
- Thread starter Lebowski
- Start date
Lebowski
10 MW
Can you space out the magnets more sideways, like with the space the same width as the magnets ?Miles said:So.... How is this supposed to work?
The density under the cone would ideally be higher than the flux density of the magnets... thats the goal.
So then what about a cone shaped magnet?Lebowski said:interesting tidbit of information:
http://physics.stackexchange.com/questions/17200/can-magnetic-fields-be-redirected-and-focused-at-one-point
apparently it is possible to use a cone-shaped piece of iron on top of your magnets to focus a magnetic field.
This opens the possibility to have iron cones on top of all the rotor magnets. With the fields thus focussed
to a smaller area, the center hole in the coils can be made smaller than the magnet size -> the total length
of wire for a certain amount of turns is reduced -> less resistance -> more efficiency and/or for the same losses
more power.
would be interesting to see a FEMM simulation.... now I have to figure this tool out.
Lebowski
10 MW
Can you, just for reference, show the case without cones but with the same airgap ?
speedmd
10 MW
Differences are subtle but significant IMO. The cone shape mags are showing yellow through the entire gap, and lots of orange internal to the magnets. Most likely the overall force is not changed too much due to the reduced area. Much fewer flux lines escaping also compared to the closer spaced magnets with cone focus adapter. The standard magnet shapes show major areas of what looks like several shades of green / lower flux levels. Interesting how much the back iron saturation changes also. Would be interesting if a slightly concave face could help focus the cone. Think Convex shape would spread thing out. Looks like sharp corners are hot spots also. Great stuff.
Lebowski
10 MW
Miles, if you don't mind (please ?) can you change the config to what I have (dimension wise) ?
N42 magnets 25mm diameter, 7 mm thick, 17mm lateral spacing, 6mm backiron, 7 mm airgap ?
then, can you try, with everything the same, 8mm lateral spacing ? (to see the effect of spacing) ?
and finally, to see if this has a focussing effect, something hal-bach inspired (with the 8mm lateral spacing):
The idea is that the extra magnets cancel out the lateral field in the airgap, focussing it more towards the centre of the main magnets
N42 magnets 25mm diameter, 7 mm thick, 17mm lateral spacing, 6mm backiron, 7 mm airgap ?
then, can you try, with everything the same, 8mm lateral spacing ? (to see the effect of spacing) ?
and finally, to see if this has a focussing effect, something hal-bach inspired (with the 8mm lateral spacing):
The idea is that the extra magnets cancel out the lateral field in the airgap, focussing it more towards the centre of the main magnets
Lebowski
10 MW
I think it's correct as I've drawn it ? The back iron thickness can be increased, the interesting bit is the field in the airgap...Miles said:
Lebowski
10 MW
this is how I see it, but I may be wrong...
the lateral field of the extra magnet (yellow) cancels out the lateral (unwanted) field of the main magnets (green)
I think (don't know if I'm correct) of magnetic fields as a sum of the fields of the individual magnets, kind of a linear superposition.
the lateral field of the extra magnet (yellow) cancels out the lateral (unwanted) field of the main magnets (green)
I think (don't know if I'm correct) of magnetic fields as a sum of the fields of the individual magnets, kind of a linear superposition.
Lebowski
10 MW
I'm starting to think maybe you're right.... best try bothMiles said:I'll try with both polarities
Lebowski
10 MW
hm, not really an improvement... and without the extra magnets ? and the bigger latteral spacing ?
Lebowski
10 MW
and the larger spacing as I have it now ?
Yep yours is definately better, but I'm guessing the extra flux is just due to the extra magnet, not due to focussing.
It's interesting though, if you consider Lorentz forces it would seem that it makes sense to have 25mm (main magnets)
worth or wiring in the airgap, with only about 8mm (narrow extra magnets) center hole in the wiring.
now I have 22mm center hole and 15mm wiring in the airgap. it would be nice to see the magnetic field of the current setup.
Yep yours is definately better, but I'm guessing the extra flux is just due to the extra magnet, not due to focussing.
It's interesting though, if you consider Lorentz forces it would seem that it makes sense to have 25mm (main magnets)
worth or wiring in the airgap, with only about 8mm (narrow extra magnets) center hole in the wiring.
now I have 22mm center hole and 15mm wiring in the airgap. it would be nice to see the magnetic field of the current setup.
Lebowski
10 MW
17mm... please also read the extra comments I just added to my previous post. What do you think ?Miles said:
Lebowski
10 MW
Miles said:The last example was with 17mm spacing.
Need to think more about this but I have to work now
magnet centre-to-centre maybe, I mean 17mm empty space between the magnets (42mm spacing ?)
nasty ain't it how work gets in the way of some good hobbying
I'm still think about the small spacing and your magnet setup, combined with 25mm of wiring in the
airgap. Looking at the pictures I have the feeling it doesn't make sense to add an iron core in the leftover 8mm...
could use a whole bunch of these to make this design:
http://www.supermagnete.ch/eng/Q-40-10-10-N?img=4
4 side by side for the main magnet with one on its side inbetween... or have custom 25x8x8 mm ones made
I wonder, what if we take your proposed situation but get rid of the 'focussing' magnet and just make the main
magnets so big that they practically touch ? Which situation would be better ?
