You should understand that not all  transformers are NOT bidirectional!
The primary is often well coupled to the core, and can excite the core well=
..
THe secondary is a bit more isolated and can not excite the core as well.

On Sep 5, 2011, at 9:40 AM, Electron wrote:

>=20
> Hello,
> is it normal that an isolation transformer gets very hot (~60C) even with=
out
> a load?
>=20
> I have built one using two spare 160VA transformers: 230V->32V =3D 32V->2=
30V of
> course the two transformers are identical, just wired as pri->sec=3Dsec->=
pri
>=20
> I needed it since my oscilloscope is not isolated from ground, and this m=
akes
> some measuring impossibile without the isolation transformer.
>=20
> Meanwhile I noticed that my 'scope is CAT II, i.e. designed to work on ci=
rcuits
> directly connected to the low-voltage installation (MAINS).
>=20
> Could there be any problems about floating the ground connection on mains
> powered scopes? I have been using it this way for days but I haven't died
> yet, was it just out of luck? :D However I get much more "usefulness" fro=
m
> my scope through the isolation transformer and no ground. :P
>=20
> But then I thought: did I really need the isolation transformer? Couldn't
> I just cut the 'scope's ground wire instead?? :P
>=20
> With kind regards,
> Mario
>=20
> --=20
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  *
  |  __O    Thomas C. Sefranek  wa1rhp@comcast.net
  |_-\<,_   Amateur Radio Operator: WA1RHP
  (*)/ (*)  Bicycle mobile on 145.41 MHz.

ARRL Instructor, Technical Specialist, VE Contact.

http://www.harvardrepeater.org


--=20
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