For copper busbars, IEC 61439-1 and common engineering practice recommend 1. Busbar sizing for continuous current starts with selecting a material (copper: 1,700 micro-ohm-cm, or aluminium: 2,800 micro-ohm-cm resistivity) and determining the current density. These standards specify the parameters that should be considered when sizing busbars, including current rating, short-circuit. Since 1. 39 A/mm² is safely below the typical 1. Use the IEC 60949 adiabatic formula: $S ge frac {I_k times sqrt {t}} {k}$ Example: For a 50 kA fault for 1s, required area is 350. Conductivity of 35 MS/m is lighter and also cheaper but needs larger physical dimensions. Current capacity without any exceeding safe operating temperature. Voltage drop limits: Maximum 3%. Temperature rise limits: Maximum 50°C above. The IEC 61439 standard applies to busbar assemblies that will be installed in electrical applications with a voltage rating up to 1000 V (for AC) and 1500 V (for DC).
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