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The positive carbon brush of the generator rotor wears out more easily than the negative one, and the negative slip ring wears out more easily than the positive one. By comparing the collector rings and slip rings of the positive and negative poles in the same generator, it becomes clear why this phenomenon occurs Changhui Instruments analyzes the reasons in this article. Carbon brush wear yunrun.com.cn/tech/2085.html Reasons for wear of generator rotor carbon brushes and slip rings. There are two types of wear on the working surfaces between the generator rotor carbon brushes and slip rings: one is pure mechanical wear ； First is electrical wear and mechanical wear under the action of electric current. 1. Pure mechanical wear between the generator rotor carbon brushes and slip rings: The surfaces of the carbon brushes and slip rings come into contact, and due to the spring pressure and the elastic deformation of the materials, the parts in direct contact press into one another. When there is relative sliding, friction naturally occurs, resulting in wear. If the carbon brush particles are fine and soft, carbon powder tends to adhere to the surface of the slip ring, giving it a smooth, shiny surface similar to that of a stone ground mirror. The grinding surface of the carbon brush is also smooth, resulting in less mechanical wear for both components. However, if the quality of the carbon brushes is poor, with coarse particles, or even if they contain a small number of hard particles such as emery, this will inevitably scratch the surface of the slip ring, resulting in a metallic sheen or patterns on that surface. The surface of the carbon brushes themselves will also develop scratches as hard particles break off, which in turn increases mechanical wear. http://yunrun.com.cn/upload/201807/16/201807162247328643.png 2. Under the influence of electric current, carbon brushes and slip rings suffer from both electrical wear and mechanical wear. Under the excitation current supplied by the generator’s excitation system, carbon brushes and slip rings experience not only mechanical wear but also electrical wear. Electrical wear refers to the damage to the pole surface material caused by factors such as the high temperature of arcs and discharges. And since electrical wear affects the pole faces, it also has an impact on the degree of mechanical wear. Since the current flows through the contact surface between the carbon brushes and slip rings, and the location where this current is conducted keeps changing, coupled with a high current density, the temperature at certain points becomes very high ； Furthermore, due to the high temperature of the arc, the pole surfaces on both sides melt and fall off locally; the metal turns into metal vapor, while the carbon brushes become weakened in structure and fall off as a result of oxidation and corrosion. This is what constitutes electrical wear. However, the wear pattern varies depending on the polarity. Under the action of an arc, the surface of the anode (positive electrode) becomes locally heated, causing “metal vapor” to be evaporated and leading to erosion of the anode surface; this phenomenon is known as “anode evaporation”” ； The cathode (negative electrode) emits electrons due to the impact of positive ions and high temperatures, which also causes damage to the cathode surface; this is known as \"cathode pulverization\". Due to anode evaporation and cathode pulverization, the carbon brushes and slip rings develop polarity differences depending on the direction of the current. When current flows from the carbon brush to the slip ring, with the carbon brush acting as the positive pole and the slip ring as the negative pole, this results in slight anodic evaporation on the surface of the carbon brush; carbon particles and graphite ions migrate to the surface of the slip ring, causing electrical wear on the carbon brush. The surface of the slip ring exhibits slight cathodic pulverization, with carbon particles and graphite attached, forming a lubricated, shiny mirror-like surface. Due to the smooth surface of the slip ring, mechanical wear is minimal. When current flows from the slip ring to the carbon brushes, with the carbon brushes acting as the negative pole and the slip ring as the positive pole, the result is cathodic pulverization on the surface of the carbon brushes, along with reduced electrical wear. Anodic evaporation occurs on the surface of the slip ring. A large amount of metal evaporates, causing severe erosion of its surface; at the same time, these metal particles tend to adhere to the worn surfaces of the carbon brushes, which in turn leads to severe wear on the commutator surface and the formation of streaks. In this case, the surface of the slip ring is rough, has a metallic luster, and suffers significant mechanical wear between its surfaces. Generally speaking, when the carbon brush is at the positive pole: the carbon brush experiences significant electrical wear but slight mechanical wear, while the slip ring suffers minimal both electrical and mechanical wear ； When the carbon brush serves as the negative electrode, its electrical wear is low while its mechanical wear is high; both the electrical and mechanical wear of the slip ring are significant. This is why the positive carbon brush of the generator rotor wears out easily, and the negative slip ring also wears out easily.