Specifications

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half the number of poles in the machines, as shown in Fig. 3.11 (b). In this type, however, each
coil may have twice the number of turns of a whole coil winding or two coils under a north or
south pole of the latter type may be connected in series and taped together to form one coil. The
main difference between full coil and half coil windings is in the method of making the end
connections for the coils.
3.12 CONCENTRATED WINDING : If in any winding, the number of coils/pole/phase is one, then
the winding is known as concentrated winding. In this winding, each coil side occupies one slot.
3.13 DISTRIBUTED WINDING : In this winding, number of coils/pole/phase is more than one
arranged in different slots and is known as distributed winding. In this case, each coil has same
pole pitch.
Unabalanced winding : If each pole of the same phase has unequal number of coils, then the
winding is called as unbalanced winding.
One Slot winding : In this type of winding, the slot per pole per phase will be equal to one.
Example 3.11 : For a 3 phase, 18 slots, and 6 pole machine
Slots per pole per phase = = 1.
Two slot winding : In this type of winding, the slots per pole per phase will be equal to two.
Example 3.12 : For a 3 phase, 48 slots, and 8 pole machine
Slots per pole per phase = = 2.
3.14 SINGLE LAYER WINDING : In this type of winding, as shown in Fig. 3.12 (a), each slot
contains only one coil side. It means a coil occupies two complete slots. The number of coils in
the machine is equal to half the number of slots in the stator, or rotor and armature.
3.15 DOUBLE LAYER WINDING : In this type, as shown in Fig. 3.12 (b), each slot contains two
coil sides, housed one over the other. The number of coils is equal to the number of slots in the
stator and armature.
Fig.3.12 - Single layer and double layer winding
3.16 SINGLE PHASE WINDING : The winding has only one group of coils per pole, placed in
one slot or several slots depending upon whether or not the winding is concentrated or distributed.
3.17 THREE PHASE WINDING : For three phase windings, three single phase windings are
used, spaced 120 degrees apart.
48
3×8
18
3×6