Gee Sparweb, I'm not so sure about that explanation.
He claims 6 sets of coils. This tells me that this unit is indeed 4 pole.... but half of them are phantom poles.... ie don't exist in copper terms, but do exist in magnetic terms. I think they call them consequent poles. Each set of coils will probably have 3 concentrically smaller coils making up the bigger ( effectively) wound (12 span) coil ..... to make a single pole....... so by definition I think he has 18 physical coils of wire in this thing.
Each coil group is three concentric coils of 12 slots, 10 slots and 8 slots width.... one wound inside the other...... and inside the other.
For the first 2 poles ......the first coil group takes up 12 slots like this:
Slots 1 and 12 first coil, 2 and 11 is the second and the smaller coil, 3 and 10 are used up....... leaving the 4,5,6,7,8,9 slots empty (6 inner slots of this group). There is no opposite wound pole for this pole..... we wind one pole group and get 2 poles.
??.... yep.
We get the next 2 poles of this first phase, by wiring a set of coils of the same 1-12, 2-11, 3-10 geometrically exactly opposite the first pole group, and wire it up so it is of like polarity to our first pole group.....ie. if we energise this phase group ( now 6 coils) with DC, we would see 2 N poles at the coils themselves, and 2 S poles halfway between these coil groups..... the aforementioned phantom poles
Thats how we get the 4 poles with effectively 2 coils (centric wound groups of three each).
The other two phases are the same thing but offset 120 degrees. This takes up the whole 36 slots for 18 coils. The coils are 6 groups of concentrically wound 3 coils.
In theory, if we reverse the polarity of each opposing coil group, we could have a 2 pole machine, as now we would have a N and S opposite each other and no phantom poles present so 180 degrees apart.............rather than a N opposite a N and making the phantom poles between.... making 90 degrees apart..... downside is that each pole will not cover 180 degrees of stator like a properly wound 24 slot 2 pole would.
clear as mud I suppose..... but I tried.
so I expect a 4 pole 36 slot stator with only 18 coils.
..................oztules
Edit... yes it is messy.... I'm not very good at this words to pics business