To Test or not to Test-A Case for Testing Complete Assemblies to IEC 60439-1

Low voltage switchgear is covered by IEC 60439-1 and the components within the switchgear assemblies are covered by I EC 60947. However, the successful testing of a component in accordance with I EC 60947 does not guarantee that it will perform successfully when installed in a switchboard configuration and this paper makes the case for type testing of components within assemblies as the only effective means of proving the integrity of the product. The paper firstly goes through the testing requirements of IEC 60947 and IEC 60439-1 and then identifies the areas of possible discrepancy between them. The problems of temperature rise limits are considered in detail in particular concerning the maximum operating temperatures of individual components and their actual rating when installed in a switchboard. It will then be explained why a component with a rating to IEC 60947 does not necessarily have the same rating when installed in a switchboard with higher internal ambient temperatures. The problems of short circuit testing are then considered with actual problems demonstrated concerning the different support arrangements allowed under the two standards which highlight why the only way to prove the capability of a component to operate as installed in a switchboard is to test it in the switchboard configuration. The paper concludes with proposals to clarify the requirements so that specifiers of equipment can guarantee that switchgear will meet their specified requirements especially to ensure that this can be met under all service conditions.