When the transformer is running, the magnetic flux passing through the iron core will be lost in the iron core, and the current passing through the winding will also be lost in the winding. In addition, the leakage flux caused by the winding current and the leakage flux outside the core when the core is over-excited will cause additional losses in various layouts, such as coils, core layout parts, core pieces, and oil tanks. Oil pumps for cooling equipment And electric fans are also lossy.
All kinds of losses are converted into heat. Part of this heat is used to increase the temperature of each component, and the other part is to radiate heat to the cooling medium adjacent to each component.
The insulating material used in the transformer has a certain heat life. For example, the heat-resistant grade of oil-immersed transformers is Class A, and the long-term working temperature of Class A insulating materials is 105°C.
According to the thermal aging rules of transformer insulation in GB/T 15164-1994 "Guidelines for Loads of Oil-immersed Electronic Transformers", transformer insulation is based on the popular temperature of 90 ℃, and the temperature increases by 6 ℃, the aging rate is doubled; on the contrary, The temperature drops by 6°C, and the aging rate is reduced by 1/2. This is based on GB 1094 "Power Transformers". This hot temperature corresponds to "operating at an ambient temperature of 20°C and a hot temperature rise of 78K". This is due to the fact that the ambient temperature in a year changes during the operation of the transformer. When the ambient temperature is higher than 20°C, the hot temperature will exceed 98°C; when the ambient temperature is lower than 20°C, the hot temperature will be less than 98°C.
Varelen Electric Co., Ltd