Wear form of electrical contact
In the process of breaking and closing circuit of electric contact, various phenomena such as metal bridge, arc and spark discharge occur in the contact gap, which causes metal transfer, splashing and vaporization of contact material and leads to loss and deformation of contact material. This phenomenon is called electrical wear of contact
Electrical wear directly affects the life of electrical appliances,
The electrical wear directly affect the service life of electrical appliances. Electrical contact electrical wear form basically has two kinds, namely metal transfer and arc burning loss of liquid bridge. 1. The formation of the liquid bridge and contact open circuit, the metal transfer from contact closed completely to the beginning of contact separation time, first contact number decreases, the contact stress and contact contact resistance is more and more big, it makes the contact point of current density has increased dramatically, and the resulting heat makes contact with the metal melt, forming the so-called metal liquid drop. Contact continue to disconnect the metal liquid drop stretched, forming liquid metal bridge, referred to as "liquid bridge.
Due to the asymmetry of temperature distribution along the length of the liquid bridge, and the maximum value was close to the anode, therefore, to make metal liquid and shifting from anode to cathode. Practice shows that due to the effect of metal transfer of the liquid bridge, after many times of operation, the contact of anode due to the loss of metal forming pits, YinPole is formed by metal in acupuncture, bulge on contact surface. In low current electrical appliances (such as relay), liquid bridge to contact electrical wear has an important influence. 2. The arc of contact arc of contact corrosion is very serious, arc wear than liquid bridge caused by 5 ~ 10 times higher than that of metal transfer. When load current is more than 20 a, achieve hundreds or even thousands of Ann, the arc of high temperature, the distance between the contact again
usually have electric arc, coupled with strong metal steam heat, often blow out, liquid metal from the contact surface to splash around. This kind of grindingWear loss and small power arc is different, metal vapor deposition on the contact surface contact again probability has been reduced greatly, make contact Yin and anode were serious wear and tear, due to the anode temperature higher than the cathode, anode wear is more serious.
