DC Machine Armature Winding (Hadi Saadat)

The DC machine armature windings are always of the closed continuous type of double-layer lap
or wave winding. For small machines, the coils are directly wound into the armature slots using
automatic winders. In large machines, the coils are preformed and then inserted into the armature
slots. Each coil consists of a number of turns of wire, each turn taped and insulated from the
other turns and form the rotor slot. Each side of the turn is called a conductor. The number of
conductors on a machine's armature is given by
Z = 2CNc----- (1)
Where Z = number of conductors on rotor
C = number of coils on rotor
Nc= number of turns per coil
Since the voltage generated in the conductor under the South Pole opposite the voltage generated
in the conductor under the North Pole, the coil span is made equal to 180 electrical degrees, i.e.,
one pole pitch. In a 2-pole machine 180 electrical degrees is equal to 180 mechanical degrees,
whereas in a 4-pole machine 180 electrical degrees is equal to 90 mechanical degrees.