KALOL INSTITUTE OF TECHNOLOGY& RESEARCH CENTER

PRESENTATION ON ARMATURE WINDING SUBJECT:-ELEMENTS OF ELECTRICAL

DESIGN

ENROLLMENT NO:-130260109039

●Topics to be covered……•DC WINDINGS:- ●AC WINDINGS:-

• Simplex & Duplex winding ● Introduction

• Lap & Wave windings ● single layer winding

• Basic terms related to armature windings ● Mush winding

• Dummy coils ● Double layer winding

• Equalizer connections ● Condition of designing D.L.W.

● Integral slot lap & Wave winding

● Fractional slot lap& Wave winding

●DC WINDINGS●•Lap Windings

•Armature windings are mainly of two types – lap winding and wave winding. Here we are going to discuss about lap winding.

• Lap winding is the winding in which successive coils overlap each other. It is named "Lap" winding because it doubles or laps back with its succeeding coils.

• In this winding the finishing end of one coil is connected to one commutator segment and the starting end of the next coil situated under the same pole and connected with same commutator segment.

● Lap Windings:-

● Simplex lap winding:-

•A winding in which the number of parallel path between the brushes is equal to the number of poles is called simplex lap winding.

● 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.

● Important terms related to lap winding:-• If, Z = the number conductors

• P = number of poles

•YB = Back pitch (YB = YF ± 2m) (m=multiplicity of winding)

•YF = Front pitch (m=1 for simplex lap winding)

• YC = Commutator pitch (m=2 for duplex lap winding)

•YA = Average pole pitch YB > YF for progressive lap winding Yc =1

•YP = Pole pitch YB <YF for retrogressive lap winding Yc=−1

•YR = Resultant pitch Resultant pitch (YR) = YB - YF = 2m

● Wave windings:-•Wave winding is one type of armature winding. In this winding the end of one coil

is connected to the starting of another coil of the same polarity as that of the first coil.

• This winding forms a wave with its coil, that’s why it is named as wave winding. It is also called series winding because its coils are connected in series.

● Progressive wave winding:-• If after one round of the armature the coil falls in a slot right to its

starting slot the winging is called Progressive wave winding.

● Retrogressive wave winding

• If after one round of the armature the coil falls in a slot left to its starting slot the winging is called Retrogressive wave winding.

● Important terms related to wave winding:- In simplex wave winding Back pitch(YB) and front pitch (YF) are both odd and are of same sign. Back pitch and front pitch are nearly equals to the pole pitch and may be equal or differ by ±2. + for progressive winding, - for retrogressive winding.

Resultant pitch:- Yr= YB + Yf

Commutator pitch :- Yc = Y/2

● Dummy coil:-

• The wave winding is possible only with particular number of conductors and slots combinations.

• It is not always possible to have the standard stampings in the winding shop consist of the number of slots according to the design requirements.

• In such cases dummy coils are employed. This coils are placed in the slots to give the machine the mechanical balance but they are not electrically connected to the rest of the winding.

● Dummy coil:-

● 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 further 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. 

● Equalizer connection:-

•  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. 

• To reduce the circulating current, points on the winding which should be at the same potentials are brought to the same potentials by connecting them with conductor. These connections called equalizer connections confine the circulating current to the winding, thus reducing the sparking at the brushes. It is found that circulating current flowing through the equalizer connections sets up a magnetic flux of the strong poles. This tends to reduce the higher induced voltage and makes the voltage of each path more nearly equal. 

● Equalizer connection:-• 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.

•Introduction:-• In ac machines, the stator has ac armature winding in which the alternating emf is

induced. The winding for armature of a dc machines is closed and the closed windings are always double layer type. The armature used for armature of ac machines is open.

• open layer can be either single layer or double layer. The stator winding consists of single turn or multi turn coils, arranged in slots and connected properly so as to obtain the required phase grouping. The AC winding must be properly arranged, so that the emf induced in all the phases are of equal magnitude and frequency. The emfs of all the m phases of ac machine must have identical wave-shape and displaced in time phase by (2 * pie/m).

●AC WINDINGS●

● Single layer winding:-• There are two types of single layer winding

1) Concentric winding

2) Mush winding

● Single layer mush winding is used in small induction motor.

● The winding in which the whole of the slot is occupied by one coil side or conductor of a coil is called single layer winding.

● Single layer winding are not used in d.c. machine because due to commutation problem.

• This is a single layer winding & is most commonly used for small induction motors. In this winding, All the coils have same span & each coil is wound on a former , making one coil side shorter than the other. The short coil sides are put first & then the long sides are inserted in the slots.

• The long & short coil side will take alternate slots. Also, the ends of the coil situated in the adjacent slots cross each other.

• This winding also known as “basket winding”.

● Mush winding:-

• (a) The coils should have a constant span.

• (b) There should be one coil side per slot. It means that , the number of coil side=number of slots.

• (c) There should be only one coil group per phase per pole pair.

• (d) The maximum number of parallel paths per phase should be equal to the pair of poles.

• (e) The coil span must be odd integer.

● Condition for designing a Mush winding:-

● Double layer winding:-•Double layer winding consist of two coils sides accommodated in

each slots of the stator or rotor of ac machine. In this winding, one side of every coil is placed in the top layer of the slot & the other side of the coil is placed in the bottom layer of another slot nearly a pole pitch apart. The coil used in double layer winding are diamond shaped as in the dc windings.

• In double layer windings used in ac machines , the number of coil sides/slot is invariably 2. Therefore

No. of coils(C)= No. of slots(S)

•Double layer winding can be further classified into two categories:-

1) Integral slot winding:-

when the number of slot/pole/phase is an integer , then it is called an integral slot winding.

2) Fractional slot winding :-

When the number of slot/pole & also the number of slot/pole/phase are not integer is called fractional slot winding.

● Double layer winding:-