IEC 61439-1 permits a maximum temperature rise of 70 K for uninsulated copper or aluminum conductors (busbars) when measured at a 35 °C reference ambient. For terminals connecting external conductors, the allowable thermal rise is tighter — 55 K — to protect cable insulation at. Diversity factor according to busbar standard IEC 61439-1 and 2 is shown below, Therefore, if a 22-number circuit with a total equipment requirement of 2700 A has a diversity factor of 0. Then, its main busbar circuit requirement current is 1620 A (2700 A * 0. In that case, a typical temperature rise inside a cabinet could push many of the components to their specified environmental limits, increasing the chance of failure. By the way, 35 o C is about the average. 7 cycles of 24 h each to salt mist test according to IEC 60068-2-11; (Test Ka: Salt mist), at a temperature of (35 ± 2) °C. Not many local vendors can achieve this? #4. Am I correctly interpreting the specification? as.
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