In your example, 9 coils and 18 magnets, at any given time, 2 magnets will pass over 1 coil. A north face over one coil leg, and a south face over the other leg. If you were to wire all coils in series, you would have a single phase machine, and it would have some pretty bad vibration while operating.
The same set up could be wired for two phase also where every other coil was wired in series. This would cut down on the rotational vibration some, but there would still be a fair amount.
The design that most others use is the 9 coil/12 magnet arrangement. This allows 4 magnets to pass over 3 coils at any given time. If you were to series wire the coils every 120 degrees, you get three phase.Have Fun!! RoyR KB2UHF
Because Hugh Piggott simplified something so that it could be wound without overlapping coils for a 3 phase axial machine ( 12 pole 9 coil or its derivatives), people seem to think that they can play with any combination of pole numbers and coils for some reason I don't understand. Perhaps they will drop lucky and find a better one and become famous for it?.
Virtually any number of pole/coil combinations will produce something if you connect them right but they may be bad indeed or almost useless. Why do it when tried and tested things exist.
As Roy said your 18 pole 9 coil is single phase. You can get 2 phase out of it but the ideal 2 phase winding will have 18 or 36 overlapped coils. Two phase works perfectly well but uses connecting wire less effectively and needs a messy rectifier, there may be some cases for trying it but three phase has stood the test of time so what's the point.
If it is for anything other than a simple standby generator for single phase loads single phase is best forgotten, it has little use for wind power.
Flux[ Parent ]
Huh?
He said 18 magnets. If this is a dual rotor, that's 9 poles. No such animal as a symmetrical machine with an odd number of poles.
If it's set up as 18 poles (say, a dual-rotor with magnets on one side only), you do get single phase. But taking every other coil from a single phase (ignoring for the moment that we have an odd number of coils - though we could take every THIRD one...) just gives you a single phase machine with multiple in-phase outputs.
To get "two phase" power the phases have to be at 90 degrees. For a non-overlapping-coil machine that means 4 coils to each 6 poles. (With overlapping coils you could get 6 coils per 6 poles.)
Two phase machines feeding a resistive load (presuming the poles and coils are shaped to give you a pure sine wave) are dead smooth. Rectified and charging a battery they aren't, and have more vibration than a higher phase count (though FAR less than a single phase machine.)
The advantage of three-phase compared to other phase counts is that, in the transmission lines, it uses the least copper for a given percentage of loss.[ Parent ]
