When vacuum breaker is in position closing gate, its are isolated from rightly to bear by supportive insulator, once place connective circuitry produces vacuum breaker breakdown of permanent ground connection, after breaker movement tripping operation, spot of ground connection trouble was not kept clear of again, the right insulation that has electric generatrix also wants to bear by the vacuum clearance of this breaker fracture surface; When all sorts of breakdown leave, fracture surface is touched one pair child the vacuum insulation clearance between should be able to bear or endure the effect that suffers all sorts of extensive telegram in reply to press and do not produce puncture. Accordingly, the unoccupied place insulation character between vacuum is become rise destroy voltage of arc room fracture surface, the main research task that makes breaker of vacuum of odd fracture surface develops to tall voltage grade.
The expression that vacuum spends means
Absolutely pressure the space with the rare gas under an atmosphere, call vacuum space, vacuum is spent taller namely intensity of pressure of the gas inside the space is lower. The unit that vacuum spends has 3 kinds to show pattern: ? namely tall) of mercury of a Mm, millibar (103bar) or handkerchief (Pascal: PA) . (1 hold =131 in the palm. 6Pa, what we say 1 millibar =100Pa) normally vacuum destroys the vacuum of arc room interior is spent should amounting to 10-4 to hold in the palm is to point to destroy the aeriform intensity of pressure with indoor arc is " only extremely one of Mm mercury are tall " , i.e. is 1. 31x10-2Pa.
"" of clique dark theorem also has interpret to be mensurable " of " Ba Shen, it is to show clearance voltage is able to bear or endure bear the relationship between intensity and aeriform pressure. Graph the 1 relation curve that expresses clique dark theorem shows "V" glyph, charge baric force namely increase or reduce, can rise extremely clearance insulation intensity. Its puncture mechanism still is not clear about up to now, because vacuum destroys vacuum of arc room interior spends prep above 10-4 to hold in the palm, space of so rare airy, the free travel of aeriform element is 103mm, destroy in vacuum arc room so inside the cubage of size, the machine rate that produces collision is almost 0. Won't produce collision dissociate accordingly and make vacuum clearance puncture. The experiment reachs the "V" form curve of clique dark theorem, the condition is to be below the circumstance of homogeneous field, uj of voltage of meantime unoccupied place puncture can express to be:
Uj=KLa
L------Clearence distance;
A------Clearance coefficient (the A=1 when clearance <5mm, > when 5mm, a=0. 5)
By the clique dark theorematic "V" form sees in relation curve, spend when vacuum amount to 103 inflection point appears when holding in the palm, the curve becomes even near inflection point, puncture voltage is almost invariant.
Be spent when vacuum and when clearence distance is same, its puncture voltage produces change along with material of the electrode that touch a head, intensity of electrode material machinery is high, when melting point is high, the unoccupied place puncture voltage between vacuum also rises subsequently.
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