Pick a preliminary size based on a conservative current density (J), typically 1. Let's choose a standard size of 2 x (40x8 mm) bars = 640 mm². We can check our design by calculating the actual current. The IEC 61439 standard applies to busbars, especially when they are part of low-voltage switchgear and control gear assemblies, e. Behind every reliable low voltage switchgear lineup is a design balance that is harder than it first appears: current must flow safely, heat must be controlled, internal space. 1) One package contains 2 busbar supports including inlay parts for bar thickness 5 mm and lateral finger-safe covers. Guide to Low Voltage Busbar Trunking Systems Verified to BS EN 61439-6 Guide to Low Voltage Busbar Trunking Systems Verified to BS EN 61439-6 November 2014 Guide to Low Voltage Busbar Trunking Systems Verified to BS EN 61439-6 Companies involved in the preparation of this Guide Acknowledgements. The busbar sizing calculator determines the required busbar dimensions based on the continuous current rating, short circuit withstand, and thermal limits for switchgear assemblies. The current rating is calculated from the conductor cross-sectional area, material (copper or aluminium), and maximum.