Specifications

31
Back Pitch, Y
b
: It is the distance between the two active sides of the same coil under adjacent
opposite poles. For double layer winding,
3.17
where K = any integer or fraction, added or subtracted with
, that will give the value of
Y
b
an odd integer.
Front Pitch, Y
f
: It is the distance between two coil sides connected to the same commutator
segment. It should be an odd integer.
Winding Pitch or Coil Pitch, Y : It is the distance between starting ends of two consecutive
coils expressed in terms of coil sides.
For a double layer winding, winding pitch should be an even integer.
Y =
+ 2m for lap winding 3.18
Y = for wave winding 3.19
where m = 1, 2, 3 for simplex, duplex and triplex windings respectively, P = number of
poles, and C = number of coils. + sign indicates progressive winding and – sign indicates
retrogressive winding.
3.8 LAP WINDING : When the finishing end of the first coil is connected to the starting end of the
next coil which starts from the same pole, as shown in Fig. 3.9, where the first coil started is
called as lap winding.
Fig.3.9 - Lap winding
From Fig. 3.9, for lap winding, the front pitch, Y
f
= Y
b
- Y 3.20
Example 3.9 : Determine the back and front pitches for a 4 pole lap winding with 24 slots.
Solution : P = 4, C = 24, winding type = lap
From equation 3.17, the back pitch,
(odd integer)
Commutator Segments
N1 S1
Y Y
f
Y
b
2C+2m
P
2
2 C
P
2×24
4
Y
b
= + K = + K = 12 + K = 11 or 13