Basic knowledge of electric vacuum products and the structure principle of arc extinguishing chamber

First, basic knowledge of electric vacuum products

Before understanding vacuum interrupter products, we first learn some terms and basic knowledge about electric vacuum products. The commonly used terms of electric vacuum products are as follows:

◆ Arc
◆ Vacuum and vacuum degree
◆ Vacuum arc
◆ AC vacuum arc
◆ Vacuum breakdown
◆ Arc extinguishing principle
◆ Life of vacuum interrupter

1. Arc

Arc or arc discharge is a form of gas discharge. Gas discharges are varied in nature and appearance. Under normal conditions, the gas has good electrical insulation properties. But when a sufficiently large electric field is added to both ends of the gas gap, an electric current can be caused to pass through the gas. This phenomenon is called discharge. The discharge phenomenon is related to the type and pressure of the gas, the material and geometry of the electrode, the distance between the two poles and the voltage applied at both ends of the gap. For example, under normal conditions, when the electrodes at both ends of the gas gap are pressurized to a certain extent, the electrons in the ordinary air move at high speed under the action of electric fields, produce more electrons and ions after colliding with gas molecules, and the new electrons and ions collide with neutral atoms, producing more electrons and ions, at this time, the gas begins to emit light, the two electrodes become hot, and the current rapidly increases. This change in nature is called the breakdown of the gas gap, and the voltage required is called the breakdown voltage. At this time, due to the support of the electric field, the discharge does not stop, so it is called self-sustained discharge. Arc is a form of gas self-sustaining discharge. The arc has the characteristics of high current density and low cathode potential.

2, vacuum and vacuum degree
Gas states below 1 atmosphere are called vacuum. The quantity describing the degree of vacuum is called the vacuum degree, which is expressed by the pressure of the gas.

l Atmospheric pressure = 760×133.332Pa = 1.013×105Pa (PASCAL) or 0.1013MPa

In vacuum technology, the wide vacuum degree range is divided into coarse, low, high, ultra-high and extremely high regions. Among them, the gas pressure in the high vacuum area is 10-1 ~ 10-6Pa, and the second half of this area, that is, 1.33 ×10-3 ~ 1.33 ×10-6, is the vacuum degree range usually used in the vacuum interrupter. In the high vacuum region, the number of gas molecules per unit volume is greatly reduced, the probability of collisions between gas molecules is greatly reduced, and the average distance between gas molecules is greatly increased.