Page 174 - Electrician - TT (Volume 2)

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Fig 12 Fig 13

3 phase squirrel cage induction motor winding (single

layer distributed winding)

Objectives: At the end of this lesson you shall be able to:
• explain the winding terms and calculations pertaining to single layer distributed type winding
• explain how to draw the end and coil connection diagrams
• state how to draw the ring and developed diagrams.

Distributed type winding: The most common type of winding found in 3-phase motors is the distributed type
winding. A distributed type winding is one in which the size of all the coils, coil pitch and shape will be the same
as these coils are normally former wound. By virtue of the arrangement of these coils in slots, the coils overlap
each other. Distributed winding may be of single or double layer type.
Single layer winding : Single layer winding is one in which there will be as many coils as half the number of slots.
For example 6 coils in the case of 12 slots, 12 coils in case of 24 slots, 18 coils in the case of 36 slots and so on.
In short, there will be only one coil side per slot.
Calculation for single layer distributed winding : The winding data of the distributed single layer winding will
be within the following limitation. (As an example 3- phase, 24 slots, 12 coils, 4 poles is illustrated below).
I Grouping

As in the example
No. of coils per phase = 12/3 = 4 coils/phase.
ii For whole coil connection

As in the example

iii For half coil connection

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