Coil Pitch or Coil Span

Coil Pitch also called coil span is a measure of distance (in terms of armature slots) between the two either sides of a coil.

Full Pitched Winding

If the coil pitch is equal to the pole pitch then such a type of winding is said to be full pitched winding. For such a winding, the coil pitch is 180 electrical degrees and the either sides
of the coil lie on opposite poles. Hence the induced e.m.f. in the coils is maximum.
For a 4 pole electrical machine with 32 slots, the coil pitch is calculated as, 32/4=8 slots.

Fractional Pitched Winding

If the coil pitch is less than the pole pitch then such a type of winding is said to be fractional pitched winding. For the fractional pitched windings there will a phase difference between the e.m.f. inducted in the two sides of the coil. Then the total e.m.f is the vector sum of e.m.f. which is less than that a full pitched winding.