AHMEDABAD INSTITUTE
OF TECHNOLOGY
DC MACHINE WINDING TERMS & DESIGN

Prepared By,

(1) 130020109048

(2) 130023109003
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(3) 140023109001

(4) 140023109002
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(5) 140023109003

(6) 140023109004
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(7) 140023109005

(8) 140023109006
MR URVISH MEVADA
GUIDED BY
JIGNESH PATEL
HOD
DC machine winding terms & design
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Basically Armature winding of a Dc machine is wound by one of the two
methods, Lap winding and lap winding
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The difference between these two is merely due to the end connections and
commutator connections of the conductor.
DC machine winding terms & design
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Terms related to DC winding:
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Pole pitch: It is defined as number of armature slots per pole. For example, if there are 36
conductors and 4 poles, then the pole pitch is 36/4=9.
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Coil span or coil pitch (Ys): It is the distance between the two sides of a coil measured in terms
of armature slots.
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Front pitch (Yf): It is the distance, in terms of armature conductors, between the second
conductor of one coil and the first conductor of the next coil. OR it is the distance between two
coil sides that are connected to the same commutator segment.
DC machine winding terms & design
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Back pitch (Yb): The distance by which a coil advances on the back of the armature is called as
back pitch of the coil. It is measured in terms of armature conductors.
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Z = the number conductors
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P = number of poles
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YB = Back pitch
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YF = Front pitch
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YC = Commutator pitch
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YA = Average pole pitch
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YP = Pole pitch
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YR = Resultant pitch
DC machine winding terms & design
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Resultant pitch (Yr): The distance, in terms of armature conductor, between
the beginning of one coil and the beginning of the next coil is called as resultant
pitch of the coil.
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Armature winding can be done as single layer or double layer. It may be simplex,
duplex or multiplex, and this multiplicity increases the number of parallel paths.
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The induced emfs in the different paths tend to differ slightly due to the nonuniformities in the magnetic circuit.
D.C machine winding terms & design
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Lap winding:
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Then, the back and front pitches are of opposite sign and they cannot be equal. YB = YF ± 2m
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m = multiplicity of the winding.
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m = 1 for Simplex Lap winding
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m = 2 for Duplex Lap winding When,
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The commutator pitch for the lap windings is given by
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yc = ±m, m = 1,2,
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The increase in the number of parallel paths in the armature winding brings about a problem of
circulating current.
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One method commonly adopted in d.c. machines to reduce this problem is to provide equalizer
connection.
D.C machine winding terms & design
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The number of parallel paths formed by the winding
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equals the number of poles. The number of conductors that are connected in
series between
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the brushes therefore becomes equal to Z/2b
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Thus the lap winding is well suited for high current generators.
In a symmetrical winding the parallel paths share the total line current
Equally
Simplex lap winding
In this type of winding finish F1 of the coil 1 is connected to the start S2 of
coil 2 starting under the same pole as start s1 of coil 1.
We have back pitch yb =2c/p=k.
Where c= number of coils in the armature,
p=number of poles,
K=an integer to make yb an odd integer.
Duplex Lap Winding
A winding in which the number of parallel path between the brushes is twice the
number of poles is called duplex lap winding.
Advantages of Lap Winding
1. This winding is necessarily required for large current application
because it has more parallel paths.
2. It is suitable for low voltage and high current generators.
Disadvantages of Lap Winding
1. It gives less emf compared to wave winding. This winding is
required more no. of conductors for giving the same emf, it results
high winding cost.
2. 2. It has less efficient utilization of space in the armature slots.
Simplex wave winding
In this type of winding finish F1 of the coil 1 is connected to the start sx of coil x
starting s1 of coil 1.
Wave winding:
In wave winding the end of one coil is not connected to the beginning
of the same coil but is connected to the beginning of another coil of the same
polarity as that of the first coil as shown in fig. 7.
Important rules for Wave winding:
1. Yb (Back pitch) and Yf (Front pitch) must be approximately equal to Yp (Pole
pitch)
2. Yb and Yf must be odd.
3. Yb and Yf may be equal or differ by ±2. + for progressive winding, - for
retrogressive winding
4. Yc = (Yb + Yf ) / 2 and should be a whole number.
Dummy coils:
The wave winding is possible only with particular number of
conductors and poles and slots combinations. Some times the standard
stampings do not consist of the number of slots according to the design
requirements and hence the slots and conductor combination will not
produce a mechanically balanced winding. Under such conditions some
coils are placed in the slots, not connected to the remaining part of the
winding but only for mechanical balance. Such windings are called
dummy coils.
Equalizer rings or Equalizer connections
in Lap winding:
This is the thick copper conductor connecting the equipotential points of
lap winding for equalizing the potential of different parallel paths. Sequence
diagram or ring Diagram: The diagram obtained by connecting the conductors
together with their respective numbers. This diagram is used for finding the
direction of induced emf and the position of brushes
Ex.: Draw the winding diagram of a D C Machine with 4 poles, 14 slots, progressive,
double layer lap winding. Show the position of brushes and direction of induced emf.
Soln:
Number of poles = 4 ;
Number of slots = 14,
Number of conductors = 14 x 2 = 28
Pole pitch = Number of conductors/pole = 28/4 = 7
We have pole pitch = (Yb + Yf ) / 2 = Yp
Hence
(Yb + Yf) = 14 (Yb - Yf ) = 2
Solving above equations
Yb = 8 and Yf = 6
back pitch yb = 2c/p ± k
For lap winding both Yb and Yf must be odd and differ by 2 Satisfying the above
condition Yb = 7 and Yf = 5 (Winding diagram and ring diagrams are shown below)
At the back Yb = 7
coil
connected side
to coil side
At the front yf =5
coil connected side
to coil side
At the back yb =7
At the front yf = 5
coil connected side Coil connected side
to coil side
to coil side
1+7=8
3+7=10
5+7=12
7+7=14
9+7=16
11+7=18
13+7=20
15+7=22
8-5=3
10-5=5
12-5=7
14-5=9
16-5=11
18-5=13
20-5=15
22-5=17
17+7=24
19+7=26
21+7=28
23+7=30
25+7=32
27+7=34
26-5=21
28-5=23
30-5=25
32-5=27
34-5=29
Thank you