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How do you work out how many magnets you would need to a given stator count free information for all
newbie-from-pa Newbie Joined: 20/06/2008 Location: United StatesPosts: 8
Posted: 11:22pm 02 Jul 2008
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The windmills I built with air core type stators I used 9 coils and 12 magnets. Another stator I built has 12 coils and 16 magnets. You have to match the size of the magnetic rotor to the stator. When find the size of the magnetic rotor, the magnets must be at least the thickness of the magnet apart and the number of magnets should have the same number of north poles as south poles. If you have 24 magnets on a magnetic rotor 12 should be north and 12 south.
GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127
Posted: 04:29am 03 Jul 2008
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On what basis do you state this?
I would go to say that the magnets could be the thickness of the air gap apart. On my design, I have 12.5mm thick magnets and a 3mm air gap [axial flux] with 2.5mm average space between adjacent magnets. There are many axial flux designs with 18-19mm air gaps, or more, between the twin rotors, so the magnets may need to be spaced as much or more than the magnet thickness apart. An engineer in this field could explain the relationship. .. .. Gordon.
Edited by GWatPE 2008-07-04become more energy aware
Gill Senior Member Joined: 11/11/2006 Location: AustraliaPosts: 669
Posted: 10:32am 03 Jul 2008
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G'day hoodlem,
I think the ratio is N : N+1
where N = the number of phases
with the N side of the ratio being stator coils
and the N+1 being magnets(alternating North/South)
So for 3 phase the ratio is 3 : 4
for 7 phase it's 7 : 8
Hence our old F&P being 3 phase has
Stator~ 3 x 14 : magnets~ 4 x 14 = 42 : 56
Old stator with new rotor is 7 phase
Stator~ 7 x 6 : magnets 8 x 6 = 42 : 48
newbie-from-pa I can tell runs 3 phase because of his ratio
9 : 12 = 3 x 3 : 4 x 3 = N x 3 : (N+1) x 3
12 : 16 = 3 x 4 : 4 x 4 = N x 4 : (N+1) x 4
Hope that helps.
Gill EDIT:
also to note is as n-f-pa says you need an even number of N & S magnets. For this to work stick with a odd number of phases to keep the magnet pairs correct.Edited by Gill 2008-07-04was working fine... til the smoke got out.
Cheers Gill _Cairns, FNQ
GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127
Posted: 11:21am 03 Jul 2008
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Hi Gill,
I will let you ponder the configuration I now present.
My alternator has 44 magnets in a dual rotor. This means 11N and 11S per rotor. There are 44 overlapping coils in the stator, arranged as 11 series coils in 4 phases. .. Gordon.become more energy aware
Gill Senior Member Joined: 11/11/2006 Location: AustraliaPosts: 669
It belongs in the locked cabinet where the medicines,poisons and ammo are stored with the big sign on the door saying
"KEEP AWAY FROM CHILDREN"was working fine... til the smoke got out.
Cheers Gill _Cairns, FNQ
GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127
Posted: 01:01pm 03 Jul 2008
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Hi Gill,
Not so, It belongs on top of a pole converting wind energy to electrickery. Gordon.
PS, Bruce will get to view a 3phase stator that did not work anywhere near as well as the 4phase I still am using. This design worked exceptionally well at 3000RPM. Probably be good for 2.5kW with around 98%efficiency as an alternator at this speed. Not much good for a windmill this way though. become more energy aware
The reason for the question is I have three phase induction motor of 2hp size with 36 stator and I would like to get the number of poles correct so it doesn't short out internally and release the spirit.
And it will need to be rewired as 3 4 or other number of phases for it to work correctly, so I am just trying to clarify everything before I make a attempt on this project so I don't blow all my money away
Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
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