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Predominant Vacuum Technology 杰出的真空技术
Vacuum interrupting technology is nowadays the dominant switching principle in medium voltage. Innovative developments are
leading to a continuously increase market growth, based on the fundamental advantages such as reliability, availability,
compactness and, lost but not least the environmental responsibility of the vacuum as a switching medium.
真空开断技术是当今中压领域主导的电弧开断技术,基于真空作为开断介质的可靠性、可利用性、紧凑性、环境友好性的优点,真
空开断作为灭弧技术主导市场需求持续增长。
Arc quenching 灭弧
During the galvanic separation of the contacts, the current to break produces a metal –vapour arc discharge. The current flows
through this metal-vapour plasma until the next current zero. Near the current zero, the arc extinguishes. The metal vapour loses
its conductivity after few microseconds already – the insulating capability of the contact gap recovers quickly. To maintain the
metal vapour arc discharge, a specific minimum current is required. If this minimum current is not reached, it will chop before the
natural current zero. To prevent unpermissible switching overvoltage while switching inductive circuits, the chopping current must
be limited to the lowest possible values. Using a special contact material, the chopping current in vacuum circuit –breakers is just
2 to 3A. Due to the fast recovery of the contact gap, the arc is safely quenched even if the contacts sparate right before a current
zero. Therefore, the arcing times in the last-pole-to-clear are 15ms as a maximum. Depending on the breaking current and the
interrupter dimensions, different contact geometries are used.
在触头开断过程中,断开的电流会产生金属蒸气电弧放电。电流流过金属蒸气等离子体,直到下一个电流过零。在过零点附近,电
弧熄灭。金属蒸气在几微秒后失去导电性–触头间隙的绝缘能力迅速恢复。为了维持金属蒸气电弧放电,需要特定的最小电流。如
果未达到此最小电流,它将在自然电流零之前截断。为防止在开关电感电路时出现不允许的开关过电压,必须将截断电流限制在可
能的最低值。使用特殊的接触材料,真空断路器中的截留值仅为 2 至 3A。由于触头间隙的电压快速恢复,即使触头在电流过零之
前变小,电弧也可以安全地熄灭。因此,最后一个开断电极的电弧放电时间最长为 15ms。根据分断电流和断路器尺寸,使用不同
的触头几何形状。
Axial Magnetic- field application in VB Series breaker 纵向磁场
The arc remains diffuse even with high currents due to the axial magnetic field. The dis-type contact surfaces are uniformly
stressed, and local melting is avoided. This results in a very small arc voltage ranging between 20 and 200V. for this reason, and
due to the short arcing times, the energy converted in the contact gap is very low. Because of this relatively low stress, the
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quenching system is maintenance-free. In stationary condition, the pressures in the interrupter are very low-less than 10 bar, so
that contact distances of just 6 to 20 mm are required to reach a very high dielectric strength. Apart from circuit-breakers, the
vacuum interrupter technology can also be used in contactors and switches. Today, more than 70% of all circuit-breakers
installed in medium-voltage system are based on vacuum interrupter technology.
由于纵向磁场,即使在高电流下,电弧仍保持扩散状态。 盘型触头面烧蚀均匀,避免了局部熔化。这样会产生非常小的电弧电
压,范围在 20 至 200V 之间。 因此,由于电弧持续时间短,在触头间隙中转换的能量非常低。 由于烧蚀相对较低,因此灭弧系统
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无需维护。 在静止状态下,灭弧室中的压力非常低,小于 10 bar,因此仅需 6 至 20 mm 的触头间距离即可达到很高的绝缘强
度。 除断路器外,真空灭弧室技术还可用于接触器和开关。 如今,安装在中压系统中的所有断路器中,有 70%以上是基于真空灭
弧室技术的。
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