Running a 220v computer in a 110v environment

From: Dwight Elvey <elvey_at_hal.com>
Date: Thu Oct 7 13:20:21 1999

"Daniel T. Burrows" <danburrows_at_mindspring.com> wrote:
> The only safe way is to use a transformer that is correctly wired. US mains
> is
> 120 - neutral - 120. which gives 240 between the 2 hots. European mains are
> 240 - neutral. Both expect the neutral to be at / near ground potential. If
> you wire it to US 240 directly what was neutral in Europe will be at 120v. I
> have several isolation / step up transformers that I routinely use to
> accomplish
> this. You need to be careful how they are wired in order to have both primary
> and secondary tied correctly to neutral and the grounds MUST be kept separate
> from the neutral to meet US electrical code.
>

Hi
 When using an isolation transformer, the transformer needs
to handle the entire power. If you use an auto-transformer
arrangement, you only need half as big a transformer.
What I have done in the past is look for supply transformers
that have configurable AC for 110/120. I save these from
old supplies that would otherwise be scrap. When I need a
boost or dropping transformer, I just wire up the primaries
as an auto-transformer. I compare the core volumes of the
units transformer with the transformer that you are using
as the auto-transformer. If the core volume of the auto-transformer
is 50% as big as the units, you should have no problems with power.
You can just leave the secondaries open.
Dwight
Received on Thu Oct 07 1999 - 13:20:21 BST