>>Hmmm... I'm not familiar with hos polyfuses work - do
>>they have to have power removed to reset?  I sort-of
>>thought they'd reset when the fault current was removed.
>
>They are basicaly a type of PTC, they have a low resistance normaly,
>but under fault current conditions they heat up and the resitance
>increases greatly.  Simply removing whatever is drawing too much
>current will allow them to reset.

But they do have a thermal time constant, which is why the item would work
for a while before cutting out, and then the power would not come back
immediately after unplugging. They are ideal devices to protect against
massive overcurrent loads as they will heat up quickly, but for a load that
is close to the Polyfuse rating the heating time is quite long. When it came
to needing to power cycle the hub to get the power back, the time taken to
do that was probably long enough for the Polyfuse to cool off and lower the
resistance enough for the power to appear, especially if the power had been
left off for 5 seconds or so.

In the UK farnell and RS have both had polyfuse devices in the past. On the
Farnell CD I have they are called "resettable fuse". Looks like RS may have
them as "thermal fuse".

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