Slot pitch in dc machine. Winding Factor | Pitch Factor | Distribution Factor
In distributed winding, coil sides per phase are displaced from each other by an angle equal to the angular displacement of the adjacent slots. But a multi-turn coil may have many conductors per coil side. As we have seen that, pole pitch is equal to total numbers of armature slots divided by total numbers of poles, we alternatively refer it as armature slots per pole.
In this coil, there will be a phase difference between induced emfs in two sides, less than o.
That means, after placing one side of the coil in a particular slot, after how many conjugative slots, the other side of the same coil is placed on the armature. The distribution factor Kd given by equation is for the fundamental component of emf.
The number of slots per pole per phase is m. In this case, the coil sides lie under opposite poles, hence the induced e. Pole Pitch Definition of Pole Pitch The pole pitch is defined as peripheral distance between center of two adjacent poles in DC machine. Before going through this section, we should understand some basic terms related to armature winding of DC generator.
In practice, coil pitch or Span as low as eight tenth of a Pole Pitch, is employed without much serious reduction in emf. But before doing this, the meaning of the following terms used in connection with armature winding should be clearly kept in mind. Hence, the total e.
A single-turn coil will have two conductors. Therefore, it must be less than unity. Definition of Coil Span Coil span is defined as the peripheral distance between two sides of a full time slot, measured in term of the number of armature slots between them.
A 3rd harmonic component of the flux wave, may be imagined as produced by three poles as compared to one pole for the fundamental component. Fractional-pitched windings are purposely used to effect substantial saving in the copper of the end connections and for improving commutation.
Similarly, we place all conductors of opposite side of the coil in another single armature slot. Hence, it is equal to 1, 2, 3, 4 etc. This distance is measured in term of armature slots or armature conductor come between two adjacent pole centers. Coil and Winding Element With reference to Fig. Obviously, the number of winding elements is twice the number of coils.
Such a winding is not much used. Commutator Pitch It is the distance measured in commutator bars or segments between the segments to which the two ends of a coil slot pitch in dc machine connected. Obviously, commutator pitch is equal to the number blackjack betting spread bars between coil leads.
Single-layer Winding It is that winding in which one conductor or one coil side is placed in each armature slot as shown in Fig. Hence resultant terminal voltage of the coil is vector sum of these two emfs and it is less than that of full-pitched coil. As seen from Fig.
So, the resultant emf of the winding is the phasor sum of the induced emf per coil side. As a matter of precaution, it should be kept in mind that all these pitches, though normally stated in terms of armature conductors, are also sometimes given in terms of armature slots or commutator bars because commuta- tor is, after all, an image of the winding.
Pitch of a Winding Y In general, it may slot pitch in dc machine defined as the distance round the armature between two successive conductors which are directly connected together.
Alternatively, the front pitch may be defined as the distance in terms of armature conductors between the second conductor of one coil and the first conductor of the next coil which are connected together at the front i. Total attention is given for designing a 3 phase alternator winding design, for 5th and 7th harmonics.
Both front and back pitches for lap and wave-winding are shown in Fig. If the coil span is less than the pole pitch, then the winding is referred as fractional pitched.
Pole-pitch It may be variously defined as: Induced emf per coil side is Ec. This number is known as coil span. Thus, the total terminal voltage of the coil will be nothing but the direct arithmetic sum of these two emfs.