The power factor of transformers produced by regular factories is 0.8. Therefore, the large mixed load of 320KVA dry-type transformer is 256KW. Generally, it is recommended to be equipped with about 200KW. Of course, if it is a pure inductive load, it can only be equipped with about 100-150KW. Because the starting current of the inductive load is 3-5 times of the running current. The short-term overload resistance of the transformer can reach 2-3 times, but the temperature rise of the long-term overload transformer is relatively high, which will accelerate the aging of the insulation layer, and even the danger of breakdown!
The temperature of a normal working dry-type transformer reaches 95 degrees, which is already considered high. No more load can be added. Low-voltage equipment generally requires that the temperature rise should not exceed 60 degrees (ie: ambient temperature + 60 degrees). Too high temperature will accelerate the aging of the equipment insulation and shorten the service life. The limit value of 12 5K is H-class insulation. The national standard "Dry-type Transformer" GB6450-1986 stipulates the temperature rise limit of dry-type transformers. For the coils of dry-type transformers, when class A insulating materials are used, when the limit operating temperature is 105°C, the high temperature rise should be less than 60K; when class E insulating materials are used, when the limit working temperature is 120°C, The high temperature rise should be less than 75K; when the class B insulation material is used, its limit operating temperature is 130℃, and the high temperature rise should be less than 80K; when the class F insulation material is used, its limit working temperature is 15 5℃, The high temperature rise should be less than 100K; when the H-class insulating material is used, its limit working temperature is 180℃, and the high temperature rise should be less than 125K; when the C-class insulating material is used, its limit working temperature is 220 At ℃, the high temperature rise should be less than 150K.
