IEC/TR 60890 1st Edition, January 1, 1987
A Method of Temperature-rise Assessment by Extrapolation for Partially Type-Tested Assemblies (PTTA) of Low-Voltage Switchgear and Controlgear
Includes all amendments and changes through Amendment 1, February 1995
Additional Comments: BILINGUAL * W/D S/S BY IEC TR 60890
Published By:International Electrotechnical Commission (IEC)
The following method is applicable to enclosed PTTA or partitioned sections of PTTA without forced ventilation.
Notes 1. - The influence of the materials and wall thicknesses usually used for enclosures are negligible on the steady state temperatures. The method is therefore applicable to enclosures made of sheet steel, sheet aluminium, cast iron, insulating material and the like.
2. - For open-type and dead-front FTTA, no temperature-rise assessment is needed if it is obvious that no excessive air temperatures are likely to arise.