ARMATURE WINDINGS

Presenter Name- Kumar GoswamiB.E.(ELECTRICAL ENGG.)

• LAP windings1

• WAVE windings2

Types of Armature Windings

Introduction

Lap winding- In lap winding, the finishing end of one coil is connected to a commutator segment and to the starting end of the adjacent coil situated under the same pole and so on, till all the coils have been connected. This winding is known as lap winding because the side of successive coils overlap each other.

• Simplex Windings1

• Multiplex Windings2

Types of LAP Windings

Simplex windings

In the simplex winding there are many parallel paths or circuits through the winding as there are field poles on the machine.

• Duplex windings1

• Triplex Windings2

Multiplex Windings

Double and Triple windings are used on armature designed for supply of large currents at low voltage.

The purpose of such a winding to increase the number of parallel paths enabling the armature to carry a large total current.

At the same time reducing the conductor current to improving the commutation condition.

Double winding consist of two similar simplex windings placed in the alternator slots on the armature and connected to alternator commutator segments,

Triple winding consist of three similar windings occupying every third slot and connected to every third commutator segment.

Important Points regarding lap Windings

The coil or back pitch Yb must be approximately equal to the pole pitch ie. Yb=Z/P where z is the number of conductors on armature and p is the number of poles.

The back pitch Yb should be either lesser or greater than front pitch Yf by 2m where m is the multiplicity of the winding.

ie.Yb =Yf+2m where m=1 for simplex winding m=2 for duplex winding m=3 for triplex winding

When Yb>Yf the winding progress from left to right and so known as progressive winding.

When Yb<Yf the winding progresses from right to left there it is known as retrogressive winding.

The back pitch and front pitch must be odd .

The average pitch is given by Yav = Yb+Yf/2 And should be equal to the pole pitch

Z/P The resultant pitch YR is always even Ie. Resultant pitch YR=2 for simplex

lap winding YR=4 for duplex lap winding YR=6 for triplex lap winding

Diagram of 4 Pole 8 Coil Lap winding

Ring Winding diagram

Characteristics of Simplex Lap winding

The winding start from any coil side returns back to that coil side after connecting all the coil sides once hence it is singly re-entrant closed winding .

Back pitch and front pitch of all the coils remain the same and odd number.

The total number of brushes is equal to the number of poles, and the brushes are connected to the coil sides, which instantaneously lie between the poles and have no emf induced in them.

There are as many parallel paths in the armature as the number of poles.

The emf between +ve and –ve brushes is equal to the emf generated in any of the parallel paths,I Z is the total number of armature coil sides and P is the number of poles, then armature coil sides connected in series in each path=Z/P

Total generated emf E =E M F generated per path =Average emf per coil side *Z/P

eav* Z/P Round the complete armature

winding, the resultant emf is zero , so that there will be no circulating current round the closed winding.

Duplex winding

Wave winding

The ends of each armature coil are connected to commutator segments some distance apart, so that only two parallel paths are provided between the positive and negative brushes.

Simplex Wave Winding

Number of conductors in each path = Z/2 The generated emf is equal to the average

emf induced in each conductor *Z/2 E= eav * z/2 Current flowing through the each conductor

is equal to the current per path Ia/2 where Ia is the armature current.

The resultant emf round the circuit is zero.