What about the temperature grade of dry type transformer

The insulation grade refers to the heat resistance grade of the insulating material used, which is divided into a, e, B, F and H levels. The specific allowable temperature rise standard of each insulation grade is as follows: maximum allowable temperature (℃) a: 105 e: 120 B: 130 F: 155 H: 180 winding temperature rise limit (℃) a: 60 e: 75 B: 80 F: 100 h: 125 epoxy castables for dry-type transformers have different grades such as F and H. Generally, the resistivity of epoxy resin has no problem, there are some differences in breakdown voltage, but the difference is not big. Class H is mainly used in dry-type transformer. At present, more companies produce class F dry-type transformer, but with the large-scale transformer, the heat-resistant requirements are higher and higher, so the demand for H-class dry-type transformer is more.

　　Dry type transformer is widely used in local lighting, high-rise buildings, airports, docks, CNC mechanical equipment and other places. Simply speaking, dry-type transformer refers to the transformer whose core and winding are not immersed in insulating oil. The cooling methods are divided into natural air cooling (an) and forced air cooling (AF). Under natural air cooling, the transformer can operate continuously for a long time under rated capacity. When forced air cooling, the output capacity of the transformer can be increased by 50%. It is suitable for intermittent overload operation or emergency overload operation; due to the large increase of load loss and impedance voltage during overload, it is in non economic operation state, so it should not be in continuous overload operation for a long time.