Three rules for maintenance of quality onan transformers
1. Allowable temperature
When the quality onan transformer is running, its coil and iron core produce copper loss and iron loss, and these losses become heat energy, which increases the temperature of the iron core and coil of the quality onan transformer. If the temperature exceeds the allowable value for a long time, the insulation will gradually lose its mechanical elasticity and cause the insulation to age.
The temperature of each part of the quality onan transformer is different. The temperature of the coil is the highest, followed by the temperature of the iron core. The temperature of the insulating oil is lower than the temperature of the coil and the iron core. The oil temperature of the upper part of the quality onan transformer is higher than that of the lower part. The allowable temperature in the operation of the transformer is checked according to the upper oil temperature. For a transformer with class A insulation in normal operation, when the ambient air temperature is up to 400C, the limit operating temperature of the transformer winding is 1050C. Since the temperature of the winding is 100C higher than the oil temperature, in order to prevent the deterioration of the oil quality, it is stipulated that the oil temperature of the upper layer of the transformer should not exceed 950C. Under normal circumstances, to prevent the insulating oil from over-oxidizing, the upper oil temperature should not exceed 850C. For transformers with forced oil circulation water cooling and air cooling, the upper oil temperature should not often exceed 750C. (The maximum allowable value of the oil temperature of the upper layer of this transformer is 800C)

2. Allowable temperature rise
Only monitoring the oil temperature of the upper layer during the operation of quality onan transformers cannot guarantee the safe operation of the transformer. It is also necessary to monitor the temperature difference between the oil temperature of the upper layer and the cooling air—that is, the temperature rise. The difference between the temperature of the quality onan transformer and the ambient air temperature is called the temperature rise of the transformer. For A-class insulation transformers, when the maximum ambient temperature is 400C, the national standard stipulates that the temperature rise of the winding is 650C, and the allowable temperature rise of the upper oil temperature is 550C. As long as the temperature rise of the transformer does not exceed the specified value, the transformer can be guaranteed to operate safely within the specified operating years under the rated load. (The transformer can operate continuously for 20 years with rated load during normal operation)
3. Reasonable capacity
During normal operation, the power load of the quality onan transformer should be about 75-90% of the rated capacity of the transformer.