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alexander.keys1 wrote:
> terry wrote:
>
> Assuming a drill of that age is metal-cased, I wouldn't want to use it
> on 230v, not worth the risk, if the handle goes live, you can't let go.
> dangerous by the HSE, IEE Regs. etc. here in the UK.
>
That's an excellent point. I must mention that it has always had a
three prong plug and the the metal; frame is grounded. With the
transformer, which is a bit of a weight to lug around but also acts as
an extension have made sure the ground/earth is extended from the input
to the output side. It is always plugged into a grounded outlet.
The transformer also acts to isolate the input (115 volt) and output
(230 volt) windings.
However if something did short to the frame and even if the transformer
was plugged into one of those RCD type outlets or GFI (Ground Fault
Interrupter) as they (incorrectly to my mind) are called here, I think
you are correct. There would not be any unbalance of current between
live and neutral wires to the input side of the transformer and thus
less protection?
Gee: Been using it that way for years; but .............
Must think about that! Maybe I should NOT have the input and output
windings separated/isolated like that? In that form the transformer
handles the total load while converting it from 115 to 230. And has
never even got warm. And it's heavy. I put an old suitcase handle on
top to carry it around!
Another form would be to have a voltage-bucking arrangement using a 1
to 1 transformer. Whereby the 115 volt input is supplemented by another
115 from the transformer to have 115 + 115 = 230 volts. In that case
the transformer would supply half the power (wattage) but it's winding
would have to carry the total output current.
Now; thinking out loud that 'might' allow any current unbalance, due
to a fault to the metal frame of the drill to be detected by the
RCD/GFI outlet into which the transformer is plugged.
By the way the idea of using 110 volt tools from a transformer with its
centre point earthed sounds like a good practice. Maximum voltage to
ground/earth/structure etc. being 110/2 = 55 volts RMS or about 78
volts peak.
Thanks for the thoughtful input. Terry
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