Page 172 - Electrician - TT (Volume 2)

ELECTRICIAN - CITS ELECTRICIAN - CITS

Fig 5 Fig 6

Half coil winding : A half coil winding is one in which the number of coils per phase is equal to half the number
of poles in the machines. Half coil winding is generally done in the winding of ceiling fans, double speed motors
etc. Refer to Fig 7.
Single layer winding : In single layer winding each slot contains only one coil side as shown in Fig 8 and the
number of coils in the machine is equal to half the number of slots in the stator or armature. In single layer winding
the coil pitch is usually taken in odd numbers.

Fig 7 Fig 8

Double layer winding : In double layer winding each slot contains two coil sides (i.e.one upper and one lower)
as shown in Fig 9 and the number of coils is equal to the number of slots in the stator.
Balanced winding : When the coil groups contain the same number of coils per phase per pole the winding is
termed as ‘balanced winding’. It is also known as ‘Even Group’ winding and is shown in Fig 10.

Fig 9 Fig 10

Unbalanced winding : If the coil group contains an unequal number of coils per phase per pole then the winding
is called ‘unbalanced winding’. It is also sometimes called ‘odd group’ winding and is shown in Fig 11.
It is important that there must be an equal number of coils in each phase whether the winding is balanced or
unbalanced as shown in Figs 10 and 11.

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