Page 160 - Electrician - TT (Volume 2)

ELECTRICIAN - CITS

The resultant pitch is the sum of the front and back pitches. Y = Y + YF
R B
• The number of coil sides must satisfy the following relations.
Z = P x Y ± 2 where P is the number of poles.
A
• In the case of simplex wave winding the number of parallel paths `A’ is equal to 2 only, irrespective of
the number of poles. However the number of parallel paths increases in multiples of the plex of the
windings.

Eg. A = 2 x plex.
Considering the above points, only an armature having designated slots can be wound for
wave winding.

• Two brushes are necessary, but as many brushes as there are poles may be used, and they must be
set so that they short-circuit only the coils cutting no flux.
• The brushes must be wide enough to cover atleast `m’ segments where ‘m’ is the ‘plex’ of the winding.
Calculations : The following calculations are made for finding out winding pitches and coil connections
with commutator segments for simplex wave winding.
Example

Number of commutator segments 7 Nos.
Number of slots 7 Nos.
Number of poles 2 Nos.
Type of winding Wave.
Winding table

1 The number of coils = Number of commutator segments = 7 coils.
2 The number of conductors or No. of coil sides = No. of coils x 2 = 7 x 2 = 14 conductors.

No.of slots
3 Pole pitch Y P No. of poles 7/2 3.5 slots,
say 3 slots

No.of conductors
Also, Y P No. of poles 14/2 7 conductors

4 No. of conductors/slot = 14/7 = 2 conductors/slot. Hence, the winding is double layer.

Z 2
5 Average pitch Y A P
14 2
16/2 8 (for progressiv e winding).
2
14 2
12/2 6 (for retrogress ive winding).
2
Hence Y = Y = 8 or 6.
C
A
6 Taking Y = 8 for progressive winding we have
A
2Y = 2 x 8 = 16 = Y + Y
A B F
Y Y = 2
F
B
Y + Y = 16.
B
F
Hence back pitch Y = 9 and front pitch Y = 7.
B F
Taking YA= 6 for retrogressive winding we have
2Y = 2 x 6 = 12 = Y + Y F
B
A
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CITS : Power - Electrician & Wireman - Lesson 86-92