Cooling System Failure
Cooling failure is often a contributing cause, not necessarily the final failure itself.
Typical problems:
Fan failure
In forced-air cooling:
· Fan motor failure
.Control circuit failure
. Contactor failure
· Bearing problem
Pump failure
In forced-oil systems:
· Pump motor failure
· Bearing damage
· Blockage
· Electrical supply failure
Radiator problems
Blocked air passages
. Oil leakage
.Corrosion
. Restricted oil flow
Failure chain:
Cooling equipment failure - oil/winding temperature rises ->insulation ageing accelerates - dielectric strength decreases -internal fault risk increases
Therefore, cooling-system failure should be analyzed together with:
· Load
· Top-oil temperature
· Winding temperature
· Ambient temperature
· Alarm/trip history