1. Elements of Electrical Design HASMUKH GOSWAMI COLLEGE OF ENGINEERING
( )
Armature Winding
PREPAID BY : - Guide by : -
1.Jay Chikani Prof. Raj Patel
2.Dipesh Shah (Electrical Dept., HGCE)
3.Vijay Dudhat
4.Probas Hazra
5.Pradipsinh Jadeja
HASMUKH GOSWAMI COLLEGE OF ENGINEERING

2. Contents Introduction Types of AC armature winding
Types of DC armature winding
Equalizer connections
Example of Lap & Wave winding

3. Introduction
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.

4. Types of Armature Winding
AC Armature Winding
Close winding
Open winding
Split winding
DC Armature Winding
Lap Winding
Wave Winding

5. Closed 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.

6. Open winding
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.

7. Split winding
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’

8. LAP WINDING 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

10. Wave winding 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

12. Equalizer connection
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

13. “Equalizer connection is needed in lap winding armature but not in wave winding “ why ?
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.

15. Ac armature winding
A.C single phase windings
A.C three phase windings

16. Example of lap winding
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 = = ) 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.

18. Example of wave winding
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 = =) 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. ( =) 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.

20. THANK YOU