Compared with other circuit breakers, the working principle of vacuum circuit breaker is different from that of arc extinguishing medium. There is no conductive medium in vacuum, which makes the arc extinguish quickly. Therefore, the spacing between the dynamic and static contacts of the circuit breaker is very small.
Insulation characteristics of vacuum
Vacuum has strong insulation characteristics. In vacuum circuit breakers, the gas is very thin, the free travel of gas molecules is relatively large, and the probability of mutual collision is very small. Therefore, collision dissociation is not the main reason for true space gap breakdown, but the metal particles precipitated by the electrode under the action of high-strength electric field are the main factor causing insulation damage.
The insulation strength in vacuum gap is not only related to the size of the gap and the uniformity of the electric field, but also greatly affected by the properties of electrode materials and surface conditions. Under the condition of small distance gap (2-3 mm), the vacuum gap has higher insulation characteristics than high pressure air and SF6 gas, which is the reason why the contact opening distance of vacuum circuit breaker is generally small.
The influence of electrode materials on breakdown voltage is mainly manifested in the mechanical strength (tensile strength) of materials and the melting point of metal materials. The higher the tensile strength and melting point, the higher the insulation strength of the electrode under vacuum.
working principle
When the high vacuum air current flows through the zero point, the plasma quickly diffuses and extinguishes the arc to complete the purpose of cutting off the current.
Post time: Aug-04-2022