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Homebrewed Electricity => Wind => Topic started by: MattM on October 21, 2017, 08:28:05 AM

Title: Halbach Array?
Post by: MattM on October 21, 2017, 08:28:05 AM
The Halbach Array is a configuration to concentrate magnetic influence directionally.  Has anyone used in a wind turbine?

from wiki: "A Halbach array is a special arrangement of permanent magnets that augments the magnetic field on one side of the array while cancelling the field to near zero on the other side. This is achieved by having a spatially rotating pattern of magnetisation."

(http://www.gaussboys.com/store/media/wysiwyg/halbach/HalbachDrawing.gif)
Title: Re: Halbach Array?
Post by: tanner0441 on October 21, 2017, 09:10:13 AM
Hi

The way I see it looking at your diagram, you may have more concentrated magnetic power but you reduce the number of effective poles. Plus you would need square magnets.

Brian
Title: Re: Halbach Array?
Post by: joestue on October 21, 2017, 01:16:00 PM
Theoretically by doubling the volume of magnet and using a halbach array, you can get an air gap flux density of 1.4T, from regular neodymium magnets that would otherwise get you an air gap flux of 1T.

The increased air gap squared, is what improves the torque and power density of the motors that a halbach array is used in.

Its not cost effective to use a halbach array when the size of the motor is not a constraint, and the magnets are the largest expense.

Furthermore the space between the magnet poles is only about 10-20% of the length of the pole in a normal motor. so you've only got space to add 10-20% more magnet.
Title: Re: Halbach Array?
Post by: MattM on October 21, 2017, 01:53:46 PM
Am I missing something here.  It looks like you could use more magnets of smaller size to get the effective number of poles.  The cost of magnets seem to grow somewhat exponentially as they increase in size and power.  I would think this pattern would in that sense be cost-effective.
Title: Re: Halbach Array?
Post by: joestue on October 23, 2017, 07:30:09 PM
Smaller magnets are more expensive usually. Furthermore the width of the magnet is usually 150 electical degrees, so yes you can fit a magnet oriented sideways between them but its only a 20% increase in magnetic volume. not a cost effective way to go about things, when simply making the entire machine larger gets you more power for the same volume of magnet.
Title: Re: Halbach Array?
Post by: Spdlmt150 on November 24, 2017, 11:38:05 AM
This is a subject I have wondered about for quite a while.

(http://www.gaussboys.com/store/media/wysiwyg/halbach/HalbachDrawing.gif)

View the above as a single magnet. Not multiple. One pole on each side, but one more concentrated than the other.

Assembly of them would be a lot to keep track of. I have made a few to tinker with and it's rather startling how the forces are altered.

I believe that there are a lot of possibilities for increasing output/decreasing size & weight using them.

I have a project which has been in the works for a couple years now using them, and have the mag discs assembled. One side is a beast, one side is nearly nonexistant.

I hope some day to finish off the stator & assemble it to provide impressive output numbers, but time hasn't been allowing that.