David Lee brought next idea :
But you must never use the cable whilst tightly coiled up (unless you have
deliberately overspecified its capacity). A coiled cable has a much higher
AC impedance due to induction and can overheat alarmingly. I have seen a
coiled 13A extension cable melt with a 3kW load! Typically a 9m extension
rated 13A unwound is derated to only 8A when fully wound.

The inductive heating is tiny compared to its heating as a result of
resistive heating. Basically the fact that it is coiled means that it
cannot dissipate much heat to the surrounding air and it then
overheats.



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Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk