Table 2. - Limiting observable temperature rise of indirectly cooled and directly water-cooled salient pole
synchronous generators and synchronous generator/motors for hydraulic turbine applications - directly
cooled machines manufactured after 1982
Method of Water-cooled windings
temperature Class B insulation
determination temperatures (°C)
(1) Temperature of cold coolant Detector or thermometer.
45 - 50
(Note 1) (Note 2)
(2) Temperature rise of directly cooled Coolant
armature windings (Note 3) (Note 2)
(3) Temperature rise of directly cooled Resistance.
55 - 50
field windings. (Note 2)
(4) Temperature rise of cores and Detector or thermometer. 85 -80
mechanical parts in contact
with or adjacent to insulation
(5) Temperature rise of collector rings. Thermometer.
(6) Temperature of miscellaneous parts such as amortisseur windings, rotor surface, brush holders,
brushes, etc., may attain such levels as will not injure the machine in any respect.
Note 1. - The method of coolant temperature measurement shell be optional with the manufacturer
unless otherwise agreed upon. Only one method of temperature measurement shall be required in any
Note 2. - Cold coolant temperatures shall be provided within the range of 45 to 50 °C, at the
manufacturer's option, so long as compensating adjustments are made in the rise of the respective parts
so that the sum of the cold coolant temperature and respective part rise does not exceed 100 °C for water
Note 3. - Temperature rise of coolant at the outlet of the hottest coil shall be considered the observable
temperature rise of the directly cooled armature winding.
Note 4. - Temperature of the core and mechanical parts in contact with or adjacent to insulating mate-
rial including that of the winding and of core laminations shall not exceed the values in the table.
Temperature of other metal parts, including structural members and shielding devices in the end region, is
not required to be within the limiting temperature, provided that these parts do not appreciably influence
the temperature of insulating material either by contact or radiation. These parts may be operated at
temperatures which are considered safe for the particular metals used.
Note 5. - The values shown for item 4 are limiting regardless of the operating power factor.
9. SHORT-TIME AND EMERGENCY
During short-time emergencies, loads of 115
percent of the normal loading limit are permissible
at the discretion of the plant superintendent.
In extreme emergencies where lack of generation
might cause a system breakup, it may be
necessary to overload machines briefly in excess
of 115 percent of the loading limit and/or
7 (FIST 1-4 3/91)