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What is the Acceptable value of contact resistance for 400V LV Switchboard busbar?

Contact resistance can be measured by millivolt drop test and it has to be found by real test. But, it is not a right method to validate any busbar joints. As per IEC 61439 - 1 & 2, temperature rise of a switchboard is important and it is already validated by type test. If the temperature rise is within control, it is really not required to worry about the contact resistance of busbar joints, voltage drops etc. To control the temperature rise, right busbar architecture and device has to be chosen from the derating table provided in the Catalogue / Technical Guide and right torque has to be applied on the connection bolts. If these parameters are ensured as per Okken / Blokset design instruction, the design will be safe.
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