Switchgear assemblies current ratings

The temperature rise limits of the various parts of a switchgear assembly during continuous operation at the rated current must conform to the values in Tables 14.5 and 14.6. 

During the test the main busbars are fed at the rated current, for which the switchgear assembly is designed. They are heated naturally and therefore no resistance of the main bus need be measured. The busbars are shorted at one end and the current is fed from the other through a variable-current injection set at a reduced voltage of 3-10 V, or enough to achieve the rated current. The arrangement saves on power requirement and consum-... 

This will be carried out under similar parameters of room condition and the type of test voltage wave to those for a switchgear assembly (Section 14.3.5). The current in each phase should be within 2% of the specified test value (rated current). 

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