colin wrote:

its a 4 phase motor I wound it myself, well im in the procees of doing so
...
it had 16 slots so trying to fit 3 phase windings in seemed awkward so I hit
upon 4 phase,
where each winding is shifted by one slot or 45 electical degrees on the
stator,
making 2 pole pairs.
(snip)

each winding is in 4 parts (ie 2 pole pairs)
but I since realised they are not all on the same magnetic path so putting
them in series
or parallel is not quite like doing the same with turns on a transformer.

If you had 4 isolated AC phases, you could connect 8
windings in a phasor octagon (half of each phase winding as
parallel sides of the octagon) with the 4 phases connected
across opposite corners. But that doesn't work for 4 half
bridges, without 4 isolation transformers. I think this
might smooth out the torque pulsations, by sharing current,
phase to phase, around the circle. This method outs each
drive phase across two parallel paths, each containing 4
coils in series, so it is a good way to use low count windings.

The Y equivalent is an 8 branch star, with the same need to
drive 4 pairs of isolated phases. This arrangement does not
alter the torque pulsations, because, even if left floating
(or the star, not even connected together), symmetry forces
the center node to have no AC.

But if you just wire it up as half of that star (only one
side of each center tapped pair), you can common the
lopsided center and drive each of the 4 ends with one of
your half bridges and have the same as the last.

But if you tie the 4 'center' ends together, but float this
node, the ripple will be reduced as this node finds its
voltage as a combination of the 4 drive phases returning
through each other. instead of through the common center
node. I could be all wet, here. I admit that 4 phases
makes my head hurt.