Page 179 - Electrician - TT (Volume 2)

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In Fig 8 coil 1 is placed in slot No.1 and the other coil side of the same coil is left over the stampings. To avoid
damage to the left out coil side, a leatheroid paper of width larger than the width of the core is placed between
the core and the coil as shown in Fig 8. After placing the coil side in the slot use the awl to fold the insulation
paper (slot liner) one side over the other, slip the separator paper over the folding and then slip the formed fibre
or bamboo wedge over the top of the coil. The wedge should extend about 3 to 6 mm beyond the slot liner. The
procedure is shown in Fig 9.

Fig 8 Fig 9

Some prefer to wedge the slots temporarily till all the coils are inserted and the winding is tested for grounding.
Once the test results are o.k., then permanently wedge the slots.
In the next step left coil side of coil 2 is placed in slot number 47 (leaving slot No.48 which is adjacent to slot No.1)
and the right coil side of coil 2 is left in the core. (Fig 8) Next place left side of the coil 3 in slot number 45 and leave
the right side of the coil over the core. Remember to extend the leatheroid paper insulation between the core and
the coil. By examination it will be found that the left out (right) coil side of coil No.3 which has left coil side inserted
in slot No.45 should be inserted in slot 2 according to the assigned coil pitch. Now insert the left out right coil side
of coil 3 in slot No.2 as shown in Fig 10.
In general, unless the left out coil side of any coil falls, according to the assigned pitch, next to the occupied slot,
proceed further to insert one coil side only. Again proceed to insert the left coil side of coil 4 in slot No.43 and the
right coil side of coil 4 in slot No.48 as shown in Fig 11.

Fig 10 Fig 11

Proceed likewise to fill up the slots and complete the insertion of coils in the slots.
Insertion of coils in double layer (lap) winding
Let us consider a 3-phase machine with 24 slots, 24 coils, 4 poles and having a slot pitch of 1-6 and a coil pitch
1-12 in terms of coil sides.
ASSUMPTION: Individual coils numbering 24 are former wound and kept ready . Procedure given
below is for the developed winding diagram shown in Fig 12.

Accordingly Fig 13 shows the numbered slots. Table 1 shows the position of the coil sides in the slots. The coil
sides in the bottom are given odd numbers and the coil sides of top are given even numbers.

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