In other words one coil sides is placed in each armature slot. The brushes of a generator must be set in the neutral plane; that is, they must contact segments of the commutator that are connected to armature coils having no induced emf. Two Layer Armature Winding In other types of armature Winding, arrangement every armature slot is occupied by two coil sides, one on upper half and other on lower half of the slot.
That means all conductors of one side of armature slots definition particular coil must be placed in one single slot only. If the coil is made up of more than one turn of conductor, it is referred as multi turn coil. The exact distribution of the windings and selection of the number of slots per pole of the field greatly influences the design of the machine and its performance, affecting such factors as commutation in a DC machine or the waveform of an Armature slots definition machine.
Front Pitch Yf The number of armature conductors or elements spanned by a coil on the front is called front pitch. Although distinctly separate these two sets of terminology are frequently used interchangeably or in combinations that include one mechanical term and one electrical term.
Armature reaction is essential in amplidyne rotating amplifiers.
This number is known as coil span. Copper armature wiring enhances electrical efficiencies due to its higher electrical conductivity. At this situation, two opposite sides of the coil lie under two opposite poles.
In other words, it is the number difference of the conductors connected together at the back end of the armature. These are two principal methods by which the effect of armature reaction is overcome. 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. Pole Pitch is naturally equal to the total number of armature slots divided by the number of poles in the machine.
The effect of the armature field is to distort the generator field and shift the neutral plane. If the coil is made up of more than one turn of a conductor, we refer it as a multi-turn coil. If the coil span is equal to the pole pitch, then the armature winding is said to be full - pitched. Coil Span or Coil Pitch Coil of dc machine is made up of one turn or multi turns of the conductor.
This arrangement is referred as single layer winding. This is naturally equal to the total number of armature slots divided by number of poles in the machine.
Coil Span or Coil Pitch
Similarly, all conductors of other side of the coil are placed in another single armature slot. Whatever may be the number of armature slots definition per side of the coil, each coil side is placed inside one armature slot only.
In practice, coil pitch or Span as low as eight tenth of a Pole Pitch, is employed without much serious reduction in emf. Hence resultant terminal voltage of the coil is vector sum of these two emfs and it is less than that of full-pitched coil. In a "wave" winding, there are only two paths, and there are as many coils in series as half the number of poles.
A single turn coil will have one conductor per side of the coil whereas in multi turns coil, there will be multiple conductors per side of the coil. Before going through this section, we should understand some basic terms related to armature winding of dc generator.
Winding materials[ edit ] Armature wiring is made from copper or aluminum. The effect of armature flux on the main field is called the armature reaction.
This field is at right angles to the generator field, and is called cross magnetization of the armature. If the coil span is less than the pole pitch, then the winding is referred as fractional pitched.
Whatever may be the number of conductors per side of the coil, each coil side is placed inside one armature slot only.