Armature winding in detail

 Armature Winding

• Armature winding is always closed and double layer type closed means all winding are connected in series to form a closed circuit. the junctions of two coils terminated on copper segment called as commutator segments.
• A coil has two sides occupying distinct specified slots. To maximum induced emf, the spacing between two ends should be kept at 180° electrical. it means if one side is under North Pole then other should be under South Pole.

Coil span
spacing between the two sides of coil. The spacing is expressed in terms of number of slots between the sides.
if S is the total number of slots and P is the total no. of poles then coil span is S/P
E.g.: For 20 slots, 4 poles, coil span=5, if one side of a coil is placed in slots 3, then other end must occupy slot (3+5=8).

• A double layer winding means that each slot has two coil sides (belonging to 2 different coils). one coil is placed in lower portion of slot and other above it.
• if S=20, P=4, coil span=5, if a coil is housed in upper deck of slot 6, then other end should lie in lower deck of slot 11. Name of coil is (6-11).

Commutator pitch

The separation of coil sides in terms of number of commutator segments is called as commutator pitch (Yc).

Procedure to create Armature winding:-

1. Type of winding (lap or wave), total number of slots S and total number of poles P will be given.
2. Calculate coil span (≈S/P)
3. Calculate commutator pitch Yc

        For lap winding, Yc = ± 1 and for wave winding, Yc = 2(S+1)/P

  

    4. We have to complete the winding showing the positions of coil sides in  slots, inter connection of the coils through commutator segments using appropriate numbering of slots, coil sides and commutator segments.

    5. Finally to decide and place the stationery brushes on correct commutator segments.