Yet many old-timers still call it "IEC 949" — a quiet tribute to the first edition that brought order to a wild frontier of power electronics.
(often referred to simply as IEC 949) is the international standard titled
This is the complex part requiring the thermal properties of the insulation. The standard uses parameters: iec 949 pdf
: The adiabatic value is multiplied by this modifying factor to determine the actual permissible short-circuit current.
: Inversed temperature coefficient factor for conductor resistance at 0°C Standard Material Coefficients Yet many old-timers still call it "IEC 949"
Understanding IEC 949: Calculation of Thermally Permissible Short-Circuit Currents
Accessing the official IEC 949 PDF or its localized equivalents (such as BS IEC 949 or standard software implementations) provides engineers with several critical tools: 1. Material-Specific Constants : Cross-sectional area of the conductor ( mm2m
: This method assumes no heat is lost to the surrounding insulation during the short circuit. It uses a simplified formula for quick estimations: : Permissible short-circuit current (A). : Cross-sectional area of the conductor ( mm2m m squared : Duration of the short circuit (s). : Constant depending on the material's thermal properties.
As this example demonstrates, the non-adiabatic method provides a more accurate (and in this case, higher) rating, potentially allowing for more cost-effective designs.
The International Electrotechnical Commission (IEC) decided to act. A working group was formed, and after years of debate and refinement, was born — officially titled "Terminology for high-voltage direct current (HVDC) transmission using thyristor valves."