ATS -Withstand and Close-On Rating

[faresos]

What does it mean exactly by Close on rating (close on fault currents) for the transfer switches? I do understand the withstand part but not sure about the close on? Thanks,

 

[dkidd]

Specific overcurrent protective device test
– ATS must withstand specified current applied until overcurrent protective device clears
– After withstanding the fault current, the ATS must close into the fault using the same set of contacts
– Rated devices along with the maximum current and voltage must be declared on product markings or documentation