Paul E. Schoen wrote in message
...

"N_Cook" wrote in message
...
Phil Allison wrote in message
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"N_Cook"

This one is mounted by central coach bolt and dished disk plus rubber
disk.
In use the bolt is vertical and when amp is carried it is horizontal.
I should say I've seen the result of an amp set for USA use used on
240V
extensive areas of bare copper due to lacquer melting or burning off
and
large amounts of smoke damage.


** Now I know for sure you are a posturing BULL**** ARTIST.

The only thing that fails when a toroidal of several hundred VA is fed
with double the rated primary voltage is the damn FUSE !!!!


It was someone who brought their 160VA Alchemist APD22 Nemesis Amplifier
over from the USA, transformer survived long enough for the
electrolytics
to short , then they overloaded the primary enough to blow the , still
set
for USA use, mains fuse.

So the fuse should be about 2 amp slow blow type, which should blow within
0.1 sec at 20 amps and within 1 or 2 cycles at higher current. For 240 VAC
use, it would be about half that. But the parallel primary connection
would
also be able to handle twice the current, so the fuse should have been
adequate.

I have tested some toroidal trannies that seem to saturate quite slowly
with increased primary voltage. In a 2 kVA unit rated 240 VAC I had about
50 mA at 240V, 100 mA at 280V, and 600 mA at 320V. Of course it would have
drawn a lot more current at 2x rating, but perhaps not enough to blow a
properly rated fuse instantly. I have seen a rather severe failure in a
toroidal 480 to 240 VAC autotransformer that was connected backward to a
high capacity mains source, thus placing the protective fuse on the load
side.

Paul



I was trying to find a table or formula for toroidal inrush current versus
power rating, but nothing found. A toroidal Tx , power for power comparison
to conventional Tx, has to be larger fuse rating, to avoid blowing at switch
on or after a few switch-ons.
If a toroidal Tx has nothing wrong with it at switch one then there is more
headroom for some later failure inducing problem not to blow the fuse. But
does this headroom increase with higher wattage ? does the ratio of
practical fuse rating/ normal maximum power consumption rise with higher
wattage toroidals ?


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/