is defined as peripheral distance between center of two adjacent poles in DC machine. This distance is measured in term of armature slots or armature conductor come between two adjacent pole centers.
Definition of Coil Span
Coil span is defined as the peripheral distance between two sides of a coil, measured in term of the number of armature slots between them. 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. This number is known as coil span.
Back Pitch (Yb)
A coil advances on the back of the armature. This advancement is measured in terms of armature conductors and is called back pitch. It is equal to the number difference of the conductor connected to a given segment of the commutator.
Front Pitch (Yf)
The number of armature conductors or elements spanned by a coil on the front is called front pitch.
Alternatively, we define the front-pitch as the distance between the second conductor of the next coil which connects the front, i.e., commutator end of the armature. In other words, it is the number difference of the conductors connected together at the back end of the armature. We are showing both front and back pitches for a lap, and a wave windings in the figure below.
Resultant Pitch (Y)
It is the distance between the beginning of one coil and the beginning of the next coil to which it is connected.
As a matter of precautions, we should keep in mind that all these pitches, though normally stated concerning armature conductors, are also times of armature slots or commutator bars.
is defined as the distance between two commutator segments which two ends of same armature coil are connected. We measure commutator pitch in term of commutator bars or segment.