on 28/04/2006, David G supposed :
I have been playing around with a Tool Transformer for 110v power tools.
Using an earth leak tester I found that the earth pin on the 240 side gave a
reading on earth, neutral and live on the 110v side. I assume this is the
centre tapped earth, but am curious to know why this is so.

TIA

That is because the centre tap of the 110v side is earthed to the 240v
earth :-)

The idea is that there should be a maximum voltage to earth of 55v,
which is half of the 110v voltage of the secondary winding.

--

Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk