Why does the dry type transformer withstand voltage test hav

   Dry type transformer do withstand voltage test, because of the electric distance will "PI PI" there are three kinds of voice, the voice of air ionization "zi zi" : the voice of air lingers = "pa", was loud and crisp, with spark, insulation (or air) is the voice of the breakdown General, air discharge in three stages, the first stage is ionization, the electric field in the big point, will enter lingers stage, in a larger air will be breakdown. If it is just like the "crackling" sound of fried beans, can adhere to a minute without breakdown, in principle is in line with the requirements of the national standard. If there is the sound of "ZI ZI", but also insisted on a minute of no breakdown, in fact, is in line with the requirements of the national standard, but the risk of long-term operation of the transformer flow is greater. The main reason for the high pressure noise is that the air distance between the main empty channel (high pressure coil and low pressure coil) is not enough. E=U/D The distance between E electric field, U voltage and D electrodes. When D is small, E is large. The field strength that the air can withstand under standard air pressure and standard humidity is about 0.7kV /mm. When the electric field is greater than this value, the molecule is prone to ionization. But as long as the air doesn't break down, it doesn't conduct electricity.