On Thu, 02 Feb 2017 14:26:41 -0600, wrote:

I was looking at the commercial isolation transformers and they are very
costly, so I decided to build my own. After all, all they are is a
transformer with a power cord on the primary and an outlet (and fuse) on
the secondary. And I already have an enclosure to put it in.

I'm looking at a bare transformer to use as an 120v isolation
Transformer. (120v in, 120v out). The transformer primary is 480 / 240.
The secondary is 240 / 120.

This is for single phase 60 cycle AC. (U.S. power).

Will it work if I connect the 240 lugs on the primary to 120 volts, and
use the 240 lugs on the secondary to obtain 120 volts.
Electrically, this makes sense, but I am not 100% sure, so I thought I'd
ask.

Also, this Transformer is rated at 750 va.


The 750VA rating applies to the part at it's label voltages. If there
is a dual primary - two windings which, connected in series, will
support 480V and which, connected in parallel will support 240V, then
a primary current of 1.5A is expected in each winding under rated
operation.

Reducing the voltage does not change the current capability of these
windings. If you halve the applied voltage, you halve the throughput
power rating, in this case, to 375VA.

A less efficient winding method, with a single tapped winding, will
use different gauge wire for the 240V section of the winding.

The same considerations apply to the secondaries.

Wired as 240in to 240out will produce a 1:1 isolation transformer.

RL