ARMATURE WINDINGS

Md.Selim HabibLecturer, Dept. of EEERUET, Rajshahi-6204.

Conductor: The length of the wire lying the magnetic field and in which an e.m.f.is induced, is called conductor (inductor).

A

B

C

D

Elements of an armature winding

The length AB or CD is conductor

A turn – two conductors connected to an end by an end connector

Elements of an armature winding

Elements of an armature winding

A coil – One or more turns connected in series. The coil may be single turn or multi turn coil.

A

B

C

D

Single-turn Multi-turn

A

B

C

D

Coil sideCoil side

Coil side: Any side of the coil that cuts lines of flux.

Fig: Single turn

A single turn coil has two conductors.

Fig: Multi-turn

Coil side Coil side

Multi-turn coil may have many conductors

per coil side.

Coil side 1: 3 conductors

Coil side 2: 3 conductors

Commutator

The group of conductors of a multi turn coil is wrapped with a tape as a unit and is placed in armature slots.

Commutator

Elements of an armature windings

A winding – several coils connected in series. The complete connection and location of all the coils on the armature

Fig: Winding

Pitch: A method of measurement. Coil sides, slots and commutator segments measurements of pitch.

Elements of an armature winding

Back pitch: The number of coil sides spanned by the back end connections.

Front pitch: The distance measured along the armature from one coil side to another coil side, the ends of which are connected to the same commutator segment.

Front pitch: Yf

Back pitch: Yb

Elements of an armature winding

The angle between centers of adjacent poles is 180o (electrical)

N

N

S S

360o electrical = 180o mech

180o electrical = 90o mech

Elements of an armature windings

The angle between centers of adjacent poles is 180o (electrical)

N

N

S S

If coil sides are placed 180o electrical apart, the coil is said to be full-pitch

a

b

180oelec

a b

If coil sides are placed not exactly180o electrical apart, the winding is said to be chorded winding. This requires less copper and induces less voltage.

Single layer winding: One conductor or coil side per slot.

Two layer winding: Two conductor or coil side per slot.

Fig: Two layer winding

The most common ways of connecting coils for armature windings:

Lap winding

Wave winding

1. Simplex2. Duplex3.Triplexand so on

Simplex Lap Singly reentrant winding

Commutator bar

Coil A Coil B1. Lap refers to fact that coil B laps over coil A.

2. Simplex means coil B is placed in the slot adjacent to coil A.

3. Singly reentrant indicates that the last coil is connected to the first coil, the coils form one continuous electrical path

Windings

Elements of an armature winding

Commutator bar

Lap winding

• 1/p of total coils are connected in series• No. of poles no. of brushes no. of parallel paths• Junction point of adjacent coils are connected to commutator

segment• No. of parallel path, a=mp. Where m= multiplicity factor, p=

poles• a=1 for simplex, a=2 for duplex and so on

Duplex Lap Doubly reentrant winding

Coil B is placed two slots to the right of coil A, leaving one empty slots between them. Coil A and B are connected in series and the junction point is connected to the commutator segment.

The empty slots are then filled exactly the same manner as the first.

Elements of an armature winding

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(C1)/p

where C is the no. of commutator bars

Elements of an armature winding