Rotor plate geometry

[lifer]

Hello,

Is there any chance of "tunning" the rotor plate (axial flux generator) as to concentrate the magnetic fieldlines in the area of interest (coil legs)?

I've seen some comercial rotor plates as in the image bellow (all rights belongs to solbergavind owner):



As you can see in this picture, there is a hole between each magnet. I know that those holes are for ventilation/low mass purpose mainly but  they could also break the magnetic fieldlines path on the end-of-coils area (the bottom of each stator coil).

On top of the rotor plate I can see a similar solution (between each magnet) - to redirect the magnetic field only through coil legs.

Am I getting nuts or there are some scientific facts?!


PS: I have the possibility to CNC laser cut the rotor plates so I could ask for any profile I want.

[Flux]

If you have access to laser cutting you can choose air vent slots, it will help a little bit but not as much as you may think. Again reducing mass will make a lighter machine that is easier to get in the air but there is no other real gain.

The main benefit of laser cutting is accuracy which will make balance easier.

The only real requirement is that the disc of the circle where the magnets sit is thick enough to carry the flux, the rest of the shape is mainly cosmetic you won't see any difference in gap flux.

Flux

[gww]

If they where in a factory setting making mutiple rotors, the cuts and curves would make for easy repeatable magnet placement.

Just a thought beyond cosmetic.
gww

[Flux]

Yes , probably more important for home build as it would save a template. Probably for large scale production the factory would be tooled up to place magnets very accurately to get consistent balance.

Flux

[lifer]

Still I'm looking at that narrowed region between magnets and it seems to "guide" or concentrate the magnetic flux through that area.

What about this situation?



If there wasn't those holes between (bottom line of) magnets, some flux (leakage) could still find a path around there. Maybe it's a small percent anyway, but worth guiding them right, don't you think?!

BTW, you better use a mask for magnet placement.

[joestue]

there really isn't all that much leakage flux.
http://ruralelectrification.files.wordpress.com/2013/02/vdsvdsvds.jpg

[Flux]

Seems to be confusion about flux in the iron and leakage flux in the air. If the iron at the back of the magnets is adequately thick virtually nothing will pass where the hole would be placed.

Leakage flux in the air will be mostly determined by the strong attraction between magnets especially when both rotors are facing each other, the presence of holes in the iron around the magnets outside the flux carrying area will have negligible effect, if there is any measurable effect the holes will help but it is so small as not to matter.

Flux

[lifer]

Thank you very much, Flux! I'll go with ventilation and mass reduction only..