Page 176 - Electrician - TT (Volume 2)

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As in the above example, ‘A’ phase starts from say 1st slot
‘B’ phase should start from 1+4 = 5th slot
‘C’ phase should start from 1+4+4 = 9th slot.
VI Arrangement of coils
As the winding is in a single layer, the coil shall be placed in alternate slots i.e. if one coil side of coil number one
is placed in slot number one which is an odd number, the other coil side of the first coil should be laid in an even
number slot. Hence placement of coils should start in slot numbers 1,3,5,7,9 and so on leaving the slot numbers
2,4,6,8 and so on to receive the other coil sides of the coils.
As in the example the 12 coils are to be laid in slots (pitch = 5 slots)
1-6, 3-8, 5-10, 7-12, 9-14, 11-16, 13-18, 15-20,

17-22, 19-24, 21-26(2), 23-28(4).
VII End connections
As discussed, for grouping of coils in normal practice, the end connections shall be whole coil connection. As in
the example in Fig 1.
VIII Coil connections
In whole coil connection, the connection of the coil group shall be from finish to finish and start to start for the
group of coils.

There are several ways of connecting the coils in groups. Fig 2 shows one method and Fig 3 shows another
method. However, you are advised to check the formation of the poles with the help of a ring diagram and clock
rule. The procedure is explained in the subsequent paras.

Fig 1 Fig 2

IX Ring diagram
Cross check the end connections as follows. Write the end connection table and mark the direction of current
using the clock rule. Note that when three-phase supply is given to the windings, and if two phases carry current
inward , the third phase will carry current outward.
Referring to method 1 shown in Fig 2, the current direction in the coil sides could be marked as shown in Fig 4.
Now arrange the slots in the sequential order and mark the direction of current in the slots accordingly by arrows
which ultimately shall represent production of the required number of poles as shown in Fig 5.
Developed winding diagram: The development winding diagram will give a clear picture of the coil sides in
relevant slots grouping, coil end connections and lead termination. A 24 slots, 12 coil, 4 pole, 3 phase single layer
distributed winding development diagram is shown in Fig 6 for your guidance.

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CITS : Power - Electrician & Wireman - Lesson 86-92 CITS : Power - Electrician & Wireman - Lesson 86-92