Specifications

34
3.18 CONCENTRIC WINDING : Concentric windings are single layer windings. This winding
has two or more than two coils in a group and the coils in each group have the same centre. In
each group, the coil pitch is not equal and therefore do not overlap each other, as shown in
Fig. 3.12. The coil span of the individual coils is different. The coil span is more than a pole pitch
while the span of others is equal to or less than the pole pitch. These windings are so designed
that the effective coil span of the winding is equal to that of a winding as a full pitch winding with
some of the coils having a span greater than a pole pitch, some with less than a pole pitch but
an effective span which makes the winding behave as if it had full pitched coils.
Fig.3.14 - Concentric Winding
QUESTIONS
Part - A
Choose the Correct Answer (1 Mark)
1. The back pitch for a 4 pole, 12 slot simplex lap connected dc machine is
A) 1, 0 B) 3, 1 C) 5, 3 D) 7, 5
2. The slots per pole of a 4 pole 25 slot simplex wave connected dc machine is
A) 6 B) 24 C) 4 D) 6
3. The coils under two adjacent poles forming one coil group and one coil group per pair of
poles is called as
A) distributed winding B) mush winding C) chain winding D) concentric winding
4. The product of pitch factor and distribution factor is
A) front pitch B) winding factor C) back pitch D) coil pitch
5. The mechanical degree between adjacent poles in a 6 pole electrical machine is
A) 180
0
ε B) 180
0
C) 60
0
D) 60
0
ε
3.19 CHAIN WINDING: In this winding, the number of coils/pole/phase is more than one having
different pitches and the coils overlap each other in the form of a chain.
N1 S1
1
4
1
6