A conductor is a length of wire used in armature winding that is placed in the armature slots. It is typically made of copper and can have one or more parallel strands. It lies in the magnetic field produced by the field winding.
Two conductors connected in series are known as a turn. The other end of the two conductors is connected to the commutator segments or connected to the other turns. The emf induced in the two conductors will help each other.
A coil is the formation of one or more turns made up of a conductor. A coil consisting of one turn (two conductors) is known as a single-turn coil and more than two turns (many conductors) is known as a multi-turn coil. In a multi-turn coil, the group of wires or conductors are wrapped together with tape.
- Coil Span or Coil Pitch:
The distance between the two sides of a coil or distance between the two conductors of a turn in a coil is known as coil span or coil pitch.
- Pole Pitch:
The distance between the two adjacent pole centers is known as the pole pitch of the machine.
- Full-Pitch Coil:
A coil is said to be fully pitched when the coil span is made equal to the pole pitch of the machine. In other words, the distance between the two coil sides of a coil will be equal to the distance between the centers of two adjacent poles. A pole can be of many coils but there will be maximum emf induced in the full-pitched coil since the coil sides of a coil lie under opposite poles.
- Front Pitch:
The distance between the second conductor and the first conductor of two adjacent armature coils connected in series is called front pitch. It is denoted by Yf.
- Back Pitch:
The back pitch is similar to that of coil span or coil pitch i.e., the distance between the two coil sides of a coil. It is the distance between the armature conductors, which a coil advances on the back of the armature. It is denoted by Yb.
- Commutator Pitch:
It is the distance measured between two commutator segments to which starting and ending terminals of a coil are connected. It is denoted by Yc and measured in terms of commutator bars or segments.
- Single-layer Winding:
In single-layer winding, each armature slot occupies only one coil side.
- Double-layer Winding:
In double-layer winding, two coil sides (two conductors) of different coils are placed in the same armature slot. Here, the two coil sides are placed one upon another with an equal portion of the armature slot occupied by them.