In message , David Looser
writes
"J. P. Gilliver (John)" wrote in message
...
In message , Mortimer
writes:
[]
While we're talking about electrical safety, what is the current (scuse
that unintentional pun) advice on extending the lead of a freezer? I know
you have to use cable that is rated for 13A (1.5 mm^2 wire rather than 1
mm^2) and conventional extension cables must be unrolled to avoid
inductive heating. But providing you use a cable of the correct
[]
I don't _think_ it's _inductive_ heating they're that concerned about -
just air cooling, or rather the lack of it when a cable is wound onto a
reel (and tightly, as it often is).
--

Indeed. It's a common error to assume that the reason that cable drums
should be unwound when in use is something to do with inductance. Possibly
because its a coil, and wire is commonly coiled up to create an inductor.
But in this case it is, as you say, simply a matter of air cooling, or more
to the point the lack of it. The inductance of an air-cored coil of
relatively few turns would be insignificant at 50Hz and in any case the
inductances of the two conductors largely cancel out.

David.



It's nothing to do with inductance. A moment's thought will show that a
cable drum of mains cable is wound non-inductively, as the forward and
return paths of the current run next to each other in the cable.
--
Chris Morriss