Instead of performing a costly full-scale temperature-rise test, IEC TR 60890 uses:
IEC TR 60890 establishes a mathematical procedure to estimate the air temperature rise inside an electrical enclosure based on internal power losses. It is primarily used when physical testing is impractical or unnecessary, such as for custom "one-off" panels or as a preliminary design check to reduce laboratory costs. Key Technical Specifications (2022 Edition) iec tr 60890 pdf
The validity area has been extended from 3,150 A to 3,200 A . 150 A to 3
Formula: P_total = P_busbars + P_breakers + P_contactors + P_auxiliaries iec tr 60890 pdf