The temperature rise of enclosed busbar trunking refers to the relative increase in temperature on the conductor or casing after stable operation with rated current. The factors affecting the temperature rise of enclosed bus ducts are the low copper content and high resistivity of copper bars. People often mention the copper content and resistivity of copper bars, which are indeed related to the current carrying capacity. Copper bars with a copper content of 99.95% or ≥ 99.93% and a resistivity of ρ ≤ 0.01777 (square millimeters/meter) are relatively high-quality copper bars in busbar copper bars.

The insulation material and shell structure have poor heat dissipation, and the structural process is well treated. The conductors of the trunking with good insulation material heat dissipation can meet the current carrying requirements after being discounted according to the design manual or electrician manual. But some products use resin casting as insulation material, or use other insulation materials with poor heat dissipation, as well as air type busbar structures and dense busbar structures with poor heat dissipation, which require more discounts. Unstable connection of connectors, increased electrical resistivity of connectors, poor contact of connectors, and increased electrical resistivity can all cause temperature rise.

The temperature rise is closely related to the skin effect inside the conductor. The heat generated by resistance is not easily dissipated, and at higher temperatures, the valence and electron operation rates are high. The circuit is not very flat, which leads to a relatively narrow electronic path and high resistance. During long-term operation of this enclosed bus duct, the joint temperature rise should be regularly checked once a year. The joint temperature rise should not exceed 70 ℃ according to the standard (ambient temperature is 40 ℃) to be qualified. All joint connecting bolts and conductive contact parts should be checked for looseness to prevent the joint from heating up due to increased resistance caused by looseness. The cross-section of the enclosed bus duct should be selected according to the long-term operating current.

Verify the short-term thermal stability and dynamic stability of the cable tray under the condition of passing through a large short-circuit cable. Due to factors such as the resistance of conductors and the AC current trend meter effect when multiple conductors are in close proximity, the passage of current through the trunking can cause heating. The allowable heating temperature for copper and aluminum bare wire troughs during long-term operation is 70 ℃. However, when their contact surfaces are reliably covered with tin (such as ultrasonic tinning), the allowable temperature can be increased to 85 ℃. Due to the limitation of this continuous heating allowable temperature, different materials and cross-sections of wire troughs are given corresponding long-term allowable current values. When selecting a cross-section, the actual long-term operating current of the wire trough should be lower than the long-term allowable current value of the selected cross-section wire trough.