On Thu, 11 Aug 2011 20:47:41 -0400, "Josepi"
wrote:

Copper takes 100% overload for a long time. In power distribution systems
hours..it can glow read hot and still survive just fine.

Aluminum is a different beast.


And although the copper may survive, the insulation very well may not.
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"whit3rd" wrote in message
...
This is probably just a matter for careful selection of a circuit breaker.
Transformers have a volt-second limit (and that means 50 Hz at rated
voltage is more likely to saturate the core than 60 Hz at rated voltage).
The volt-second limit applies to the UNLOADED transformer, though,
so a blade-welding cycle (with a nice big load on the secondary
while current is flowing in the work) is likely to be trouble-free.
If the transformer is switched on before the blade parts are butted,
it could saturate and blow the main breaker (so putting a 20A breaker
local to the unit would be more convenient if it needs resetting).

Another saturation protection would be a good fast-blow fuse (because
if it isn't the breaker or fuse that blows, it's the copper in the
transformer).