Download armature winding

Elements of Electrical Design
(2150904)
Armature Winding
PREPAID BY :  1.Jay Chikani
 2.Dipesh Shah
 3.Vijay Dudhat
 4.Probas Hazra
 5.Pradipsinh Jadeja
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Guide by : Prof. Raj Patel
(Electrical Dept., HGCE)
CONTENTS
Introduction
 Types of AC armature winding
 Types of DC armature winding
 Equalizer connections
 Example of Lap & Wave winding
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The armature winding is the main current-carrying winding in
which the electromotive force or counter - emf of rotation is induced.
The current in the armature winding is known as the armature
current. The location of the winding depends upon the type of
machine.

In the armature, an electromotive force is created by the relative
motion of the armature and the field. When the machine acts in the
motor mode, this EMF opposes the armature current, and the
armature converts electrical power to mechanical power in the form
of torque (unless the machine is stalled), and transfers it to the load
via the shaft. When the machine acts in the generator mode, the
armature EMF drives the armature current, and shaft mechanical
power is converted to electrical power and transferred to the load.

AC Armature Winding
› Close winding
› Open winding
› Split winding

DC Armature Winding
› Lap Winding
› Wave Winding

In this winding there is closed path around the armature. If
starting at an point, the winding is followed through all its
turn and the starting point is reached again. The armature
current divides itself into parallel paths.

Closed windings are always double layer windings.

A.C machine where commutator is not used so in this
case closed winding are not necessary BUT TYPE
WINDING CAN USED. Open windings may be single
or double layer. These winding are used for induction
machines and also for synchronous machines.
Generally simplex lap winding has two coil side per
slot. But most of the time there may be four or more
coil side per slot. In such case the value of back pitch
YB shall be show chosen that all the coils having coils
side in the upper layer of one slot should after form the
bottom layer of another slot
 This necessities the use of ‘split coils’

Commutator bar
• One coil between adjacent commutator
bars
• 1/p of total coils are connected in series
• No. of poles  no. of brushes  no. of parallel
paths
•
•
•
•
p/2 coils in series between adjacent commutator bars
½ of all coils between brushes
Regardless of no. of poles, there are always 2 parallel path
The distance between end coils (commutator pitch) is 2(C1)/p where
C is the no. of commutator bars
The equivalent circuit of a four point – pole dynamo with a
simplex winding. The voltage induced in each path is
assumed to both to be same and should be if the reluctance
of each magnetic path is the same, so that the lines of flux
cut by each inductor of each path are the same.
 However wear of the bearings or deflection of the armature
shaft may cause the armature to be closer to some poles and
farther from others, thus changing the length of the air gap,
and therefore the reluctance of the magnetic circuits of the
poles is not identical.
 This factors cause the voltage in the materials making up
the magnetic circuit. These factors cause the voltage in
each parallel path differ, and the unequal voltages in turn
cause flow of a circulating current through the windings
and brushes , undue heating of the armature and waste the
power


A wave windings requires no equalizer connections.
This is true because each path has conductors in series
under all poles of the dynamo. Any difference in the
lines of the flux from the poles will produce different
voltage in the inductors , but both paths will be equally
affected and the total induced voltage of each path will
always be the same.

A.C single phase windings

A.C three phase windings
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AC Lap Winding:
Development of single phase, single layer AC lap winding for a 4 pole AC machine having
24 slots.
In single layer winding, the number of coil is equal to half the number of slots on the stator,
so that each slots contains only one coil side.
We know that the pole pitch = Number of Slots/Number of Poles = 24/4=6
Slots per pole per phase, m = (24/4)x1 = 6
Number of coils C=12
Slots 1 to 6 and 13 to 18 lie under North pole regions N1 and N2 respectively. Similarly
slots 7 to 12 and 19 to 24 lie under South pole regions S1 and S2 respectively. In other
words, the first pole pair covers slots 1 to 12 and the second pole pair covers slots from 13 to
24.
For full pitch winding, angle between the two sides of the same coil is 180 degrees. 180
degrees corresponds to 6 slots.
Number of coils(or slots) per pole= 6.
The coil in slot no. 1 is to be connected to coil in slot no. (1 + slots per pole = 1 + 6 = ) 7 or
back pitch, Yb = 7, ie., if slot no. 1 is at the beginning of the first North Pole, N1, the slot no.
7 will be at the beginning of the first South Pole, S1.
The winding pitch, Y = +2 (progressive winding)
Therefore, the front pitch, Yf = Yb – Y = 5.
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Development of a single phase, single layer wave winding for a 4 pole, 24 slot ac machine.
Number of coils, C = 12
Pole pitch = Number of slots / Number of Poles =24/4 = 6
Slots per pole per phase m=6
Slots 1 to 6 and 13 to 18 lie under North pole regions N1 and N2 respectively. Similarly slots 7 to
12 and 19 to 24 lie under South pole regions S1 and S2 respectively. In other words, the first pole
pair covers slots 1 to 12 and the second pole pair covers slots from 13 to 24.
For full pitch winding, angle between the two sides of the same coil is 180degrees. 180degrees
corresponds to 6 slots.
For full pitch winding, angle between the two sides of the same coil is 180degrees.180degrees
corresponds to 6 slots.
For ac wave winding, back pitch, Yb = number of coils(or slots) per pole= 6 = front pitch, Yf.
If one side of the coil is placed in slot no. 1, the other side of the coil should be placed in slot no.
(1 + slots per pole = 1 + 6 =) 7. The finishing end of the coil side at slot no. 7 is connected to the
starting end of the coil side at slot no. (7 + 6 =) 13. Now the other side of the coil side at slot no.
13 is placed at slot no. (13 + 6 =) 19. Adding 6 to slot no. 19 gives 25, which is slot no.1, ie., 25 –
24 = 1. But a coil side is already placed at slot no. 1. So add 1 and place the coil side at slot no. 2.
Similarly, add turn by turn back pitch and front pitch and at the end of each round add Yb + 1. The
following table gives the complete winding table for a 4 pole 24 slot ac wave wound machine.