Dc Generator Machines - Lincoln Electric Classic 300 MP Service Manual

LINCOLN ELECTRIC Classic® 300 MP Service Manual
Figure E.8 – DC generator machines

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 is 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
connected to the shaft. Rotation of the armature through the magnetic field produced by the stationary
field winding induces a coil voltage in the armature winding. The voltage induced in an individual armature
coil is an alternating (AC) voltage, which must be rectified. In a conventional DC generator, rectification is
provided mechanically by means of a commutator. A commutator is a cylinder formed of copper segments
insulated from each other and mounted on, but insulated from, the rotating shaft. Stationary carbon
brushes held against the commutator surface connect the armature windings to external terminals. The
commutator provides full-wave rectification, transforming the voltage waveform between brushes and
making available a DC voltage to the external circuit.
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