Generally speaking, people still have concerns about the conductivity of insulated piercing clamps. Can such a few small thorns withstand such a large current?
We analyzed the working principle of the parallel channel clamp and the insulation piercing clamp from the principle of conducting current between conductors. The current conduction between the conductor and the conductor can be analyzed from the mechanical contact area of the conductor and the current conduction path.
1. The mechanical contact area of the conductor
From a microscopic point of view, the surface of the conductor is composed of countless uneven peaks and valleys. The smoother the surface of the conductor, the smaller the height difference between the peaks and valleys. When the two conductors are brought into contact by external force, the contact is mainly There is a form of peak-to-peak contact. Therefore, the actual mechanical contact area is much smaller than the nominal contact area of the clamp design. According to literature analysis, the real mechanical contact area is about 7% of the nominal contact surface.
2. Current conduction path between conductors
1) Under the action of external force, the active aluminum oxide layer on the aluminum interface of the two conductors is squeezed or rubbed to partially rupture it, allowing aluminum electrons to flow freely between the surface peaks to form a certain conductivity. The more the pressure is Larger, the more peak points of contact, the smaller the contact resistance.
2). The conductive ability of active aluminum oxide itself makes the undamaged area also have a certain conductivity.
3).Due to the good plasticity of aluminum, when the pressure on the two interfaces is released, part of the aluminum on the inner wall of the clamp will be plastically deformed and enter the stranded void of the outer layer of the wire, and the electrical conductivity on the electrical interface will be improved.
Due to the creep of the wire, the wire is slightly thinner and reduced in diameter, the effective contact area is reduced, and the resistance of the groove clamp is increased. The reduction of the effective contact surface is mainly caused by the reduction of the pressure on the wire by the clamp and the increase in the oxidation of the contact surface.
Therefore, in order to improve the power supply reliability of the parallel groove clamp, several parallel groove clamps are often used on site.
Therefore, we usually think that the contact of the parallel groove clamp splint is actually only point-to-point contact, and the piercing clamp relies on the piercing of the blade to enter the wire, as if a finger is inserted into the water. According to relevant literature, its contact area is more than that of the parallel groove clamp. It is more than 1 times larger. Moreover, the puncture clamp also has the advantages of convenient installation and high reliability.
The wire that has been pierced by the piercing clamp should ensure that its breaking force is not less than 95% of the original wire’s breaking force, and the wire cannot lose its due mechanical properties due to the puncture.
Post time: Nov-27-2021