description about LAP and WAVE winding in dc generator

In generators we employ two types of winding in the armature. Winding differ in the way the end connections at the front and at the commutator end. This winding each can connect in progressively and retrogressively depending upon the requirement.

difference between lap and wave windings

There are some rules to be employed while you are winding the armature they are as follows

The Front pitch and Back pitch should be approximately equal to pole-pitch i.e winding should be full pitched. But in some conditions we will use short pitched winding also. Due to full pitched winding the emf around the coils increases.
Both pitches are odd otherwise it will be difficult to place winding in the armature.
The commutator segments should be equal to number of slots or coils because the front ends of conductors are joined to the segments in pairs.
The winding should close upon itself, that means the coils should be interconnected to form a closed loop.

Simplex Lap winding:

In lap winding the finishing end of one coil is connected to commutator segment and to the starting end of another coil and soon up to all coils are connected. so this type of winding which laps back with succeeding coils called as Lap winding.

Some points regarding the connection of Lap winding:

The back and front pitches are odd and of opposite sign with difference of '2'
Both back and front pitches should be nearly equal to pole pitch
The average pitch Ya = (Yb+Yf)/2 and it equal to pole pitch (Z/P)
Commutator pitch Yc = ±1
Resultant pitch Yr is even i.e Yr = Yb-Yf
The number of slots for a 2-layer winding is equal to number of coils(i.e half the number of coil sides). The number of commutator segments are also same.
The number of parallel paths in the armature = mp where m is multiplicity and p is number of poles
For progressive winding Yb > Yf i.e Yb = Yf+2 so the commutator pitch Yc = 1 and we can find Yf = Z/P - 1 and Yb = Z/P + 1
For retrogressive winding Yb<Yf i.e Yb = Yf-2 so the commutator pitch Yc = -1 and we can find Yf = Z/P + 1 and Yb = Z/P - 1

Simplex Wave winding:

In wave winding a conductor under one pole is connected at the back to a conductor which occupies an almost corresponding position under the next pole of opposite polarity. so this type of winding progress like a series of waves so it is called as Wave winding.

Some points regarding the connection of Wave winding:

The back and front pitches are odd and of same sign
Both back and front pitches should be nearly equal to pole pitch and may be equal or differ by 2.
The average pitch Ya = (Yb+Yf)/2 and it equal to (Z±2/P) and + sign for progressive winding and - sign for retrogressive winding.
Resultant pitch Yr = Yb+Yf
Commutator pitch Yc = Ya and also Yc = (no.of commutator bars±1)/no. of pair of poles
Number of coils Nc = (PYa±2)/2

These are the winding connections we use for drum type armature in dc generator. This are the values you have to calculate before connecting the winding.

Where to use lap and wave winding:

In wave winding the emf produced is high when compared to lap winding with same poles and conductors and also the number of conductors, slots used should be more when compare to lap so, for more emf and small generators we use wave winding.

In wave winding we don't use equalizer rings but in lap winding we have to use equalizing connections for spark less commutation.

Hence for large current requirements we use lap winding and for high emf requirements we use wave winding. Here i want to conclude in single line as, the lap winding is used for low voltage and high current generators where as wave winding is used for high voltage and low current generator.

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