AS 60890:2009 pdf free
AS 60890:2009 pdf free.A method of temperature-rise assessment by extrapolation for partially type-test assemblies (PTTA) of low-voltage switchgear and controlgear
In IEC Publication 60439-1，in the series of type tests, a temperature-rise is specified.However, for certain types of assemblies for which the performance of a temperature-rise test is either not feasible or economically not justifiable a calculation of the temperature rise in the form of extrapolation from data found by tests on other assemblies may be made instead.Such assemblies are then called partially type-tested assemblies (PTTA).
Various methods of calculations can be conceived and are acceptable. The factors and coefficients set out in this report have been derived from measurements on numerous assemblies and the method has been verified by comparison with test results. The method described in this report is therefore one possible method and may for partially type-tested assemblies be used to prove compliance with the requirements of sub-clauses 8.2.1 of IEC Publication 60439-1. This report applies to PTTAs only.
The following method is applicable to enclosed PTTA or partitioned sections of PTTA without forced ventilation.
NOTE 1 – The influence of the materials and wall thickness 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.
NOTE 2 – For open-type and dead-front PTTA, no temperature-rise assessment is needed if it is obvious that no excessive air temperatures are likely to arise.
The proposed method is intended to determine the temperature rise of the air inside the enclosure.
NOTE: The air temperature within the enclosure is equal to the ambient air temperature outside the enclosure plus the temperature rise of the air inside the enclosure caused by the power losses of the installed equipment.
Unless otherwise specified, the ambient air temperature outside the PTTA is the air temperature indicated for indoor installation of the PTTA (average value over 24 h) of 35°C. If the ambient air temperature outside the PTTA at the place of use exceeds 35°C, this higher temperature is deemed to be the ambient air temperature of the PTTA.AS 60890 pdf free download.
