On May 27, 5:14*am, KD7HB wrote:

Hi, Lloyd.
The voltage ratios have to be the same, either direction, as they are
physical quantities(turns counts). What doesn't work it the KVA
rating, according to the electrician that installed the transformer to
operate our convection oven for soldering circuit boards. He said to
de-rate the KVA 10%. We have been running a transformer backwards to
get 480 from 208 for about 4 years, now. 24/7.

Paul

True the voltage levels at no load have to be the same. But the
voltage ratios do not have to be 2:1. As Don and Lloyd say, the
smaller transformers are designed with a ratio slightly off of 2:1.
That is so at the rated load, with some voltage reduction because of
losses in the transformer, the voltage ratio is 2:1.

But it reminds me of the difference between an engineer and a
physicist. If a physicist enters a room and sees a naked girl on the
other side of the room, he sighs. Because he knows that he can go
toward the girl until he gets half way there. And he can half the
distance again and again, but doing that will never get him to the
girl.

The engineer just barges in, because he knows he can get close enough.

Dan