Wave winding

 Wave winding

In wave winding the coil side is not connected back but progresses forward to another coil sides as shown in fig. b) In this way the winding progresses passing successively every N-Pole, S-Pole till it returns to coil side from where it was started. Because the winding progresses in one direction round the armature in a series of waves hence it is known as wave winding or series winding.

Important point Regarding wave winding:

1)      Both pitches Yb and Yf Should be Odd and Of the same sign.

2)      Back and front pitches must be nearly equal to the pole pitch and may be equal or differ by 2 in which case they will be one more or one less than average pitch.

3)      Commutator pitch,  Yc = Average pitch Ya

4)      Resultant pitch,  Yr = Yf + Yb

5)      The average pitch, which must be an even integer is given by

            Ya =        Z = number of conductors

                                   P = number of poles

The +Ve sign in the above formula will give progressive winding and –ve sign a retrogressive winding.

6)      For even number of pairs of poles i.e., for 2,4,6, or 8 pair pole machines:

(i)                  The average pitch may be odd or even.

(ii)                The number of coils must be odd.

(iii)               The number of commutator segments must be odd.

7)      For odd numbers of pairs of poles

i)                    The number of coils may be even or odd.

ii)                   The number of commutator segments may be even or odd.

iii)                 If the number of coils are even, Ya must be odd and Vice-Versa.

Dummy Coils: The wave winding is possible only with particular number of conductors but some times the standard armature punching available in armature winding shops do not meet the requirements of the winding as they may accommodate more than the required number of conductors. In such cases dummy (coil or) coils, or idle coils are employed. These coils are placed in slots to preserve the balance of machine but are not electrically connected to the rest of the winding.

For Example: To have a simple wave winding with 32 armature conductors in a 4-pole machine,

Ya =

But the average pitch must be an integer, so the winding is not possible with 32 conductors (of course lap winding is possible). However, if Z = 30 (or 34) conductors are possible, but in both cases two coil- sides or coil is inactive and hence is called dummy coil. The ends of dummy coil are taped and are not connected to the commutator segments.