Theory of operation, Dc generator machines – Lincoln Electric CLASSIC I SVM134-A User Manual
Page 43
DC GENERATOR MACHINES
The armature winding of a DC generator is located on
the rotating member. Current is conducted from it by
means of carbon brushes. The field winding is located
in the stator, which is stationary and excited by direct
current.
The armature coil sides are placed at opposite points
on the rotating shaft with the conductors parallel to the
shaft. The armature assembly is normally turned at a
constant speed by a source of mechanical power con-
nected to the shaft. When the armature rotates
through the magnetic field produced by the stationary
field winding, it induces a coil voltage in the armature
winding. The voltage induced in an individual armature
coil is an alternating (AC) voltage, which must be recti-
fied. In a conventional DC generator machine, rectifi-
cation is provided mechanically by means of a com-
mutator. A commutator is a cylinder formed of copper
segments insulated from each other and mounted on,
but insulated from, the rotating shaft. Stationary car-
bon brushes held against the commutator surface con-
nect the armature windings to external terminals. The
commutator provides full-wave rectification, transform-
ing the voltage waveform between brushes and mak-
ing available a DC voltage to the external circuit.
THEORY OF OPERATION
E-5
E-5
CLASSIC I
ARMATURE
SHAFT
GENERATOR
ARMATURE
SHUNT
WINDINGS
FIELD
MECHANICAL
COUPLING
SHUNT
WINDINGS
FIELD
BRUSH
BRUSH
MAGNETIC FIELD
MAGNETIC FIELD
DC CURRENT
DC CURRENT
F
I
E
L
D
C
U
R
R
E
N
T
F
I
E
L
D
C
U
R
R
E
N
T