26-06-2012, 02:19 PM
GENERATORS MAINTENANCE
2- generator maintenance.ppt (Size: 1.29 MB / Downloads: 47)
REASONS WHY GENERATORS FAIL
FOREIGN OBJECT DAMAGE
Problem: Objects can come from external sources or
failure of internal components, they can pick up energy
from the spinning rotor and do extensive damage
Prevention: Inspect on a regular basis all internal parts
that are prone to failure or can be dislodged.
Inspection tests can be a combination of visual
inspection along with ultrasonic or magnetic particle
tests on rotating components
STATOR WINDING VIBRATION
Problem: Primarily a design related problem that
affects large (>300Mw) generators which have
insufficient end winding bracing to limit the
movement of end turns.
Prevention: Proper bracing of the end winding is
required to limit motion caused by steady state and
transient electromagnetic forces.
ROTOR WINDING DISTORTION
Problem: Rotor winding distortion caused by poor end
turn blocking support design or by foreshortening of
the rotor coils. Foreshortening is caused by thermal
forces which compress rotor coils.
Prevention: Proper design of rotor coils and bracing to
support the coils under axial load is essential.
Rotors should be tested for turn to turn shorts at
operating speed.
STATOR WINDING VIBRATION
Problem: Primarily a design related problem that
affects large (>300Mw) generators which have
insufficient end winding bracing to limit the
movement of end turns.
Prevention: Proper bracing of the end winding is
required to limit motion caused by steady state and
transient electromagnetic forces.
ROTOR VIBRATION
Problem: There are many causes, turn-to-turn shorts,
rotor coil foreshortening, electrical grounds,
mechanical imbalances, overheating, etc.
Prevention: Comprehensive vibration measuring is effective
combined with a regular maintenance program.