The winding used in electrical machine can be broadly classified into two types: Concentrated Winding and Distributed Winding.
In concentrated type of winding, all the winding turns are wound together in series to form one multi-turn coil. Examples of concentrated winding are field winding for salient pole synchronous machine and DC machine. In concentrated winding, all the turns have the same magnetic axis. Primary and secondary winding of a transformer also form concentrated winding. Figure below shows one example of concentrated winding.
Since the coils are concentric in this type of winding, there is no concept of pitch factor and distribution factor for such winding. In fact, the value of pitch factor and distribution factor for concentrated winding is unity. Thus the emf induced E by working flux Ø in such type of winding having N series turns is given as below.
E = √2πfNØ
No rotational torque is produced if both field winding and armature winding are of concentrated type. Example is transformer which does not rotate.
In distributed type of winding, all the winding turns are arranged in several full-pitch or fractional pitch coils. These coils are then inserted into slots spread along the air gap periphery. Stator and rotor of Induction Machine, armature winding of synchronous and DC machine are some of the examples where distributed winding is used. Figure below depicts distributed winding.
It can be seen from above figures that, the three phase winding are distributed among the 12 slots. The induced emf in any phase is the phasor sum of individual emf induced in coils side located at different slots. For better understanding of how emf is calculated in distributed winding, please read Distribution Factor.
Difference between Concentrated and Distributed Winding
The major difference between the concentrated and distributed winding is that, concentric oils are used in concentrated winding whereas coils are spread along the air gap periphery in distributed winding.
Some of the important difference between concentrated and distributed winding are tabulated below.
|The coils of concentrated winding are co-axial. This means, all the winding coils have the same magnetic axis.
|The coils of distributed windings are not co-axial. They are rather distributed in various slots along the air-gap periphery.
|The emf induced in the such winding is independent of pitch and distribution factor.
E = 1.414πfNØ
|The emf induced in the distributed winding is dependent on the value of pitch factor Kp and distribution factor Kd.
E = 1.414πKpKdfNØ
|This type of winding is used in transformer, electromagnets etc.
|Distributed winding is used in armature winding of induction machine, synchronous machine, DC machine etc.
|For concentrated winding, the number of pole is equal to number of slots.
|Number of pole is not equal to number of slots.