Several issues with circuit breakers and high-voltage cabinets
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What is the purpose of silver plating on the moving and stationary contacts of a circuit breaker? Why are the isolation steel plates in various compartments such as the busbar room, cable room, and circuit breaker room within high-voltage switchgear galvanized?
The purpose of silver plating is to prevent oxidation and electrochemical corrosion. The oxide film has a high resistivity and is difficult to remove, especially at the joint areas; therefore, these areas are either silver-plated or tin-plated, with tin plating being more commonly used nowadays. Galvanizing partitions and similar components serves to enhance their corrosion resistance, but the galvanized layer can wear out easily. Currently, aluminum-zinc coated steel sheets are widely used; when the galvanized layer is worn away, the aluminum oxidizes to form a dense oxide film that continues to protect the steel sheet. Moreover, aluminum-zinc coated steel sheets exhibit good heat resistance, corrosion resistance, and heat reflectivity. Their main advantage is cost-effectiveness, with the only drawback being the increased difficulty in processing them.
Agree with the person above. Furthermore, when an electric current flows through the direct connection between copper and aluminum, an electrochemical galvanic cell reaction occurs, which increases the contact resistance; over time, the contact surface heats up and a failure occurs. Because chemicals such as zinc, silver, and gold have more inert chemical oxidation properties than copper. Gold is the best, silver is the next best, and zinc is the third best. Copper terminals that need to be connected to aluminum wires are generally plated with gold, silver, or zinc on their surfaces. Since gold is a precious metal, its processing cost is high. Although zinc is inexpensive, it wears easily. Therefore, when manufacturing conductive parts that require high electrical conductivity, the contact surfaces need to be silver-plated.
The silver-plated surface turns yellow and loses its luster. The tinned surface turns white and shiny. When aluminum is joined to aluminum, the oxide layer is removed, embossing is done, and a conductive paste is applied. Copper-to-copper joints are silver-plated or tin-plated and embossed. When copper and aluminum are joined, the copper is tin-plated or silver-plated, while the aluminum has its oxide layer removed and a conductive paste is applied; however, such copper-aluminum joints are not common in practice.
It is mainly to prevent arc oxidation, as arcs may be generated during disconnection or closing
Learn anytime* Ha, by the way, is tin plating okay? ? ? Is the electrical conductivity of tin lower than that of aluminum?
Tin plating is commonly used nowadays. Aluminum oxidizes easily, and its oxide film has poor electrical conductivity; therefore, when joining aluminum busbars, it is necessary to remove the oxide film from the joint surfaces before applying conductive paste.