The question is often asked, if 13A plug can take the full load of 3000VA of a SmartUPS or SURT.
This issue turns up every now and then and basically there shouldn't be any problem.  There are more issues in the UK with high voltage than with low voltage as the supply voltage there is 240V.
If we take the full load of 3000W then it would draw 12.5A at 240V.
However we, like other UPS manufacturers recommend not loading a UPS over 80% which would mean a load of 10A. Even at 200V it would take 12A and it would only begin to become a problem
at a voltage of about 185V.
A BS1362 13A Fuse is a slow blow type and is required to operate at 1.9 times rated current (24.7 A) within 30 minutes, and also that the fuse shall have a non-fusing current of 1.6 times rated
Current  (20.8 A).  For this reason the plug is well capable of taking a few amps more for a reasonable period of time and this is why a B16A MCB will often trip before the 13A fuse blows.
Where there is a voltage sag, the 13A fuse would can handle this without blowing or without damaging the plug-top.
We would also like to point out that the SmartUPS UPS units comply with IEC 62040-3 and the corresponding British Standards so there should be no problem with the electrical cords or plug-top supplied with these units.
Released for:APC Australia