Manual for Induction Motors and Generators
Trouble Shooting - 109
3BFP 000 050 R0101 REV E
8.5 Thermal performance and cooling system
There are two fundamental reasons that might cause an increase in the machine's temperature:
• The effect of the cooling system has declined
• The machine is producing excessive amount of heat.
If the machine temperature exceeds the normal values, measures should be taken to determine
which one of the above mentioned two causes is dominant cause in a particular incident.
NOTE: An excessive heat production might be caused by a winding problem or by network
unbalance, and in these cases corrective actions on the cooling system would be
ineffective or harmful.
If the winding or cooling air temperature detectors show an abnormal temperature, a check of
the cooling system has to be done. Two separate maintenance issues affect the cooling system.
The apparent part is to ensure the uninterrupted and correct operation of the heat exchanger.
This task is accomplished by periodically cleaning and checking the heat exchanger for correct
operation.
The air or water flow through the heat exchanger must also be checked. If the cooler is equipped
with an external blower fan, its operation needs also to be checked.
The less apparent but equally important part is to ensure good air circulation in the primary
cooling circuit inside the machine. This task can be fulfilled by cleaning and checking the
machine interior during overhauls or if problems arise.
Other possible causes for poor heat exchanger performance might include elevated ambient
temperature, high intake air or water temperature, and low air or water flow.
In addition, lubrication or bearing malfunction might lead to high bearing temperature. A
seemingly high temperature might also be caused by a problem in the temperature measurement
system Chapter 8.3.2 Pt-100 resistance temperature detectors.
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