No almost twice the rated voltage to any normally designed mains
transformer will cause the transformer core to heavily saturate.
This will burn the fuse or the transformer itself if it is not
It is not the insulation but the transformer core+coil design
that made for lower voltage. Most propably the transformer
will not arc at twice the normal voltage...
Tomi Engdahl (http://www.iki.fi/then /)
Take a look at my electronics web links and documents at
| It is not the insulation but the transformer core+coil design
| that made for lower voltage. Most propably the transformer
| will not arc at twice the normal voltage...
Unless the overheating due to the overcurrent due to a combination of the
greater voltage and the reduced inductance resulting from saturation were
to melt the insulation enough to compromise their the insulation integrity.
|WARNING: Due to extreme spam, googlegroups.com is blocked. Due to ignorance |
| by the abuse department, bellsouth.net is blocked. If you post to |
In which case the problem would not be the insulation, but rather the
overheating due to overload or saturation. The point was that it is unlikely
that the inulation would arc from double the voltage, especially when you
consider that the transformer is designed to pass a hi-pot test of several
Benjamin D Miller, PE
The insulation at this voltage level will have a factor of safety in the
order of 5-6. The problem is that 208V vs 120V will drive the
transformer into heavy saturation where the no load current will greatly
exceed the rated current- so I^2R losses and heating will be much
greater than normal resulting in, as Rheilly indicates; insulation has
temperature limits after which it starts to fail or burn and
let the smoke out"
The idea of "letting the smoke out" has been around around for a long
time. For a number of years experianced engineers have told me that
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nature of this smoke to find out in what way it somehow contributes to
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You will only make money if you find an easy way to put the smoke back in.
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You might saturate the core, in which case it will draw a large current. In
any event you are exceeding its design voltage. As others pointed out, it
has nothing to do with insulation. You could run it from L-N at 120V and
then feed a 2:1 step up transformer to get your 208 volts.
Benjamin D Miller, PE
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