Pay attention to the conductor material of busbars: Currently, there are three types of conductor materials—copper bars, aluminum bars, and copper-aluminum composite materials—and their prices vary significantly. In addition to purity, it’s also important to consider the mechanical properties of the material after bending. The interfacial strength of copper-aluminum composite materials directly affects their machinability and reliability. This is a critical performance parameter for copper-aluminum composite busbars. Such materials can only be used in electrical equipment if they exhibit no blistering, no noticeable orange-peel texture, no delamination between copper and aluminum, and meet the minimum requirements for interfacial bonding strength during punching and shearing processes.

1. Different manufacturing processes result in varying interface bonding strengths. When copper and aluminum are pressed together under mechanical pressure, only the atoms at the interface can be activated to form atomic bonds. After heat treatment, point connections evolve into surface connections; however, the diffusion depth is very shallow, leading to relatively low interface bonding strength. Only by fusing copper and aluminum under specific process conditions can the interface be uniformly bonded with a certain composite layer thickness, thereby achieving higher interface bonding strength. Based on extensive experiments and finite element analysis using computers, when the copper cross-sectional area accounts for 20% of the total cross-section, the cost-effectiveness is optimal. Due to the skin effect, the electrical conductivity increases significantly by 20%, hardness improves, and service life is extended. There is a certain relationship between the copper-layer cross-sectional ratio and the specific gravity of copper-aluminum composite busbars. When the copper cross-sectional area constitutes 10%, 15%, and 20% of the total cross-sectional area, the corresponding specific gravity increases by 32%, 3.63, and 3.94 (g/cm³), respectively. A simple method for determining the cross-sectional area of the copper layer is to obtain a sample, weigh it, calculate its volume, and then determine the specific gravity.

2. Use qualified products from reputable enterprises: For bus-only lanes, only products bearing the 3C mandatory certification mark should be used, and type-test reports must be provided. When making purchases, conduct thorough investigations into the manufacturer’s production scale, technical capabilities, worker qualifications, and production environment—especially the production environment. If the production environment is not clean, conductive particles may find their way into the insulation layer. While this may not matter during initial operation, prolonged use can damage the insulation layer. The economic cross-section of waterproof busbars should be selected based on the maximum long-term operating current. The short-term thermal stability and dynamic stability of waterproof busbars must be verified according to the conditions of the maximum short-circuit current. When conductors are placed close to each other, the current flowing through the waterproof busbar generates heat due to the effects of conductor resistance and the skin effect in alternating current. The long-term permissible heating temperature for bare copper and aluminum busbars is 70°C. However, when the contact surfaces are reliably coated with tin (e.g., by ultrasonic tinning), the permissible temperature limit under continuous heating can be raised to 85°C. Corresponding long-term permissible current values are provided for waterproof busbars made of different materials and with different cross-sections. When selecting components for waterproof busbars, ensure that the actual maximum value of the waterproof busbar is less than the long-term permissible current rating of the selected component.

3. According to the recommendations of busbar trunking system manufacturers, when the average annual load is relatively high and the busbar trunking system is long—such as in outdoor switchgear installations—a method based on economic current density should be adopted. The economic current density refers to the small current per unit cross-sectional area of the busbar, taking into account comprehensively busbar losses, annual maintenance costs, and depreciation expenses for both the busbar itself and associated auxiliary equipment. By dividing the economic current density by the long-term operating current (excluding overload currents), one can determine the required cross-sectional area of the busbar.

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