1. Potential Impact of Structural Characteristics of Fire-Resistant Bus Duct on Current Carrying Capacity
In order to achieve fire resistance, the structure of Fire-Resistant Bus Duct is more complex than that of ordinary bus duct. Usually, a fire-resistant insulation layer is added inside the Fire-Resistant Bus Duct. This structure occupies a certain space, which makes the heat dissipation space of the bus relatively reduced. The heat dissipation of ordinary bus duct mainly depends on the heat exchange between the bus itself and the surrounding air, and the heat dissipation path is relatively direct. The fire-resistant insulation layer in the Fire-Resistant Bus Duct is like a barrier, which hinders the dissipation of heat. For example, some Fire-Resistant Bus Ducts use ceramic fiber insulation materials with low thermal conductivity, and it is difficult for heat to be quickly conducted out. According to thermal principles, the failure to dissipate heat in time will cause the bus temperature to rise, and the current carrying capacity of the bus is closely related to the temperature. The temperature increase may limit its current carrying capacity. Therefore, from the perspective of structural characteristics, the current carrying capacity of the Fire-Resistant Bus Duct may change.
2. The influence of refractory materials on current carrying capacity
The refractory materials used in Fire-Resistant Bus Duct are one of the key factors affecting current carrying capacity. These refractory materials often have low thermal conductivity, which can prevent heat transfer when a fire occurs and protect the normal operation of the busbar. However, under normal operation, this low thermal conductivity becomes an unfavorable factor affecting the current carrying capacity. Since heat is difficult to dissipate through refractory materials, the heat generated by the busbar during the power-on process will accumulate inside. The current carrying capacity is determined based on the temperature that the busbar can withstand during normal operation. Heat accumulation causes the temperature to rise. In order to ensure the safe operation of the bus duct, the current carrying capacity has to be reduced. Compared with ordinary bus ducts, ordinary bus ducts do not have the obstruction of such refractory materials, the heat dissipation is relatively good, and the current carrying capacity is relatively small.
3. The relationship between electrical performance adjustment and current carrying capacity
In order to achieve the purpose of fire resistance in design, the electrical performance of the Fire-Resistant Bus Duct may be adjusted, and these adjustments will indirectly affect the current carrying capacity. For example, in order to enhance the fire resistance, the insulation material of the busbar may be changed or the spacing between the busbars may be adjusted. Changes in insulating materials may affect the electric field distribution of the busbar, while adjustments to the busbar spacing may affect its magnetic field distribution, which in turn affects the reactance of the busbar. Changes in reactance will affect the current-carrying capacity of the busbar. Generally speaking, when the reactance increases, the current-carrying capacity will decrease. When designing ordinary bus ducts, the main consideration is the optimization of normal electrical performance, and there is no need to consider the electrical performance adjustment brought about by fire resistance, so its current-carrying capacity is relatively stable, which is different from Fire-Resistant Bus Duct.
4. Comparison of current carrying capacity in actual applications
In actual applications, due to the combined influence of the above factors, the current carrying capacity of Fire-Resistant Bus Duct does vary compared with that of ordinary bus ducts. Many engineering cases and experimental data show that the current carrying capacity of Fire-Resistant Bus Duct is usually lower than that of ordinary bus ducts. For example, under the same busbar material, ambient temperature and use conditions, ordinary bus ducts may be able to carry a current of 1000A, while Fire-Resistant Bus Duct may only carry a current of 800A. This reduction in current carrying capacity is to ensure that the bus duct can operate safely and stably under the premise of guaranteed fire resistance performance, and meet the power supply needs of the building in special circumstances such as fire.
