Vacuum Electronic Devices
Release Time：2016/1/27 10:35:43 News Source：admin Views：8587
Vacuum interrupter, also known as vacuum tubes, high-voltage power switch is the core component. Its main role is to, through a vacuum tube excellent insulation of high voltage circuit so quickly after the power cut out and inhibit the current arc to avoid the occurrence of incidents and accidents, mainly used in electricity transmission and distribution control system, also used in metallurgy, mining, petroleum, chemicals, railways, broadcasting, communications, industrial power distribution system such as high frequency heating. With energy and materials, fire, explosions, small size, long life and low maintenance costs, reliable operation and no pollution.
Vacuum interrupter circuit breaker from the use of divided into rooms with interrupter and load interrupter switch, circuit interrupter used mainly for the power sector in the substation and power grid facilities, load interrupter switches used mainly used for power grid end-user.
Vacuum Interrupters structure mainly by gas-tight shell insulation, conductive circuits, shielding system, bellows and other parts.
1, airtight insulation system
By the glass or ceramic casings made airtight insulation, moving cover plate, fixed cover plate, stainless steel corrugated pipe insulation system composed of a gastight. In order to ensure the glass, ceramic and metal gastightness good, except when the sealing operation should have a strict process, also called the permeability material itself as small as possible and internal release gas restrictions to the minimum. The role of stainless steel bellows vacuum interrupter can not only internal and external vacuum atmospheric state separate, but also move together with the dynamic contact conductive rod in the framework of the provisions of movement, in order to complete the vacuum switch closed with breaking operation.
2, conductive system
Set conductive rod, will be run Globoidal will contact, moving contact, moving Globoidal run, moving conductive rod constitute interrupter conductive system. One set of conductive rod, will be run Globoidal will collectively set contact electrode, moving contact, moving Globoidal run, moving together, moving conductive rod electrodes, from vacuum interrupter assembled into the vacuum circuit breaker, vacuum load switch and vacuum contactors Reclosing when actuator conductive rod through the dynamic movement, so that the two contact closure, completed a circuit to connect. In order to make contact between the two to minimize contact resistance and to maintain the stability and dynamic stability interrupter under current good mechanical strength, electrical conductivity vacuum moving par-oriented units set up at one end and use a set of compression springs, to maintain contact between the two have a rated pressure. When the vacuum switch breaking current when interrupter contact separation of the two arcing in the meantime, until the current natural arc extinguished before midnight, they completed a circuit breaker.
3, shielding system
Vacuum interrupter shield system is mainly shielding extinguishers, shield and other component parts.
Shielding systems main role is:
(1) to prevent arcing contact in the course of a large amount of metal vapor and liquid droplets splash, pollution shell wall insulation to avoid vacuum interrupter shell insulation intensity dropped or produce flashover.
(2) to improve the vacuum interrupter internal electric field distribution, in favor of vacuum interrupter small shell of insulation, especially for high-voltage vacuum interrupter miniaturization significant effects.
(3) to absorb part of arc energy, condensation products arc. Especially in the vacuum interrupter breaking short-circuit current, the arc generated by thermal shielding system was largely absorbed and will be beneficial to the resumption of contact between the medium intensity. Shielding system to absorb the volume of products the greater the arc of his greater absorption of energy, which increase the vacuum interrupter breaking capacity of a good role.
4, contact
Contact is the arcing, the site of arc extinguished, the structure of materials and higher requirements.
4.1 pairs of contact materials have the following requirements:
(1) high breaking capacity. Requirements of the conductive material itself rate is high, small thermal conductivity, heat capacity, thermal capacity of low-emission.
(2) high breakdown voltage. Breakdown voltage high, medium intensity on the resumption of high benefit to the interrupter.
(3) high anti-corrosive power. That can stand the arc ablation, metal evaporation less.
(4) the ability of anti-fusion.
(5) low-closure current value, hope the following 2.5A.
(6) low gas content.
At present, vacuum interrupter circuit breaker with the contact material mostly copper-chromium alloy, copper and chromium 50 percent each. In the upper and lower contacts of the docking of the welding on the surface of a copper-chromium alloy films, the general thickness of each 3mm. Block, known as the rest of the contact with oxygen-free manufacturing can be.
4.2 Contact structures
Contact structure on the eradication of solitary room breaking ability to be greatly affected. Contact with different structures arising from the effect of different interrupter, early contact, using a simple cylindrical structure, although simple, but breaking capacity can not meet the requirements of circuit breaker, only the following 10kA breaking current, only vacuum load switches, high-voltage vacuum contactors, etc. Vacuum be adopted. At present, there is often used in bad spiral structure contact with chute goblet contact and vertical structure of the magnetic field structure contact goblet three, with the use of longitudinal magnetic field structure contact mainly goblet.
5, Bellows
Vacuum Interrupters bellows main responsibility to ensure that moving the electrode in a certain range and long-term campaign to maintain the function of high vacuum and to ensure that vacuum interrupter has a higher degree of mechanical life.
Vacuum Interrupters bellows is 0.1 ~ 0.2mm thick stainless steel made of thin-walled components. Vacuum in the division process, the interrupter bellows by stretching the role of bellows section by stress effect, so we have the life span of bellows expansion should be based on the volume and use of repeated pressure to determine.
Bellows fatigue life and working conditions of heating temperature, vacuum interrupter breaking big in the short-circuit current, the conductive heat transfer under the bellows, so the temperature bellows, when the temperature rise of up to a certain extent This will affect the fatigue strength bellows 6, the working principle
Vacuum interrupter is sealed in a vacuum of a pair of contact to achieve the power circuit to connect with the function of breaking a power vacuum devices, is the use of high vacuum dielectric Block. When its current disconnect certain values, the move, scheduled for the separation of contact in an instant, the current contraction of the separation of the contact just a point or points, the performance of inter-electrode resistance increased dramatically and rapidly rising temperatures, until the electrode metal evaporation, while the formation of a high electric field strength, leading to intense field emission and the breakdown gap created a vacuum arc, when the current close to zero, at the same time increasing contact spacing, vacuum arc plasma is fast around the proliferation of arc current zero, the contact gap of medium to quickly move from the electrical insulator, so the current was breaking, breaking the end.