IEC 61439-1:2020 is available as IEC 61439-1:2020 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.
IEC 61439-1:2020 lays down the general definitions and service conditions, construction requirements, technical characteristics and verification requirements for low-voltage switchgear and control gear assemblies. NOTE Throughout this document, the term assembly(s) (see 3.1.1) is used for a low-voltage switchgear and control gear assembly(s). For the purpose of determining assembly conformity, the requirements of the relevant part of the IEC 61439 series, Part 2 onwards, apply together with the cited requirements of this document. For assemblies not covered by Part 3 onward, Part 2 applies. This third edition cancels and replaces the second edition published in 2011. It constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: a) clarification that power electric converter systems, switch mode power supplies, uninterruptible power supplies and adjustable speed power drive systems are tested to their particular products standard, but when they are incorporated in assemblies the incorporation is in accordance with the IEC 61439 series of standards; b) introduction of a group rated current for circuits within a loaded assembly and the refocusing of temperature-rise verification on this new characteristic; c) addition of requirements in respect of DC; d) introduction of the concept of class I and class II assemblies regarding protection against electric shock.
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200A would be the overall circuit ampacity and not a 100A per pole additive equation statement. The measured voltage of 240 volts would be between each pole or phase and the measured voltage of 120 volts would be from either phase to the center-tap wire. If all the connected loads were balanced the measured amps would be equal.
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There are some unknowns here, so the below are assumptions with the given values. With the secondary voltage of 120 and the markings of 25, 75, and 167 - I would assume as you have stated that these are the kVA ratings and the 4800 is more than likely the primary voltage. Additionally, the 3-wires are either a center tapped winding, or a 2-winding transformer connected internally and only 1 connection lead brought out of the transformer. In either case the secondary voltage would be 120/240 based on your ampacity values stated above. The formula to calculate Full-Load Current with Single-Phase Transformer is = kVA x 1000 / V
Using the 25kVA transformer as an example:
25 x 1000 / 120 = 208 secondary amps or 25 x 1000 / 240 = 104 secondary amps
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