View Single Post
Old 15th Nov 2017, 4:35 pm   #8
daviddeakin
Hexode
 
daviddeakin's Avatar
 
Join Date: Apr 2007
Location: W Yorks, UK.
Posts: 406
Default Re: 'Alternative' isolation transformer

Don't forget about magnetising power. The first transformer will have to supply the magnetising power to the second transformer, so this needs to be subtracted from the first one's VA rating. Bigger transformers often need a lot of magnetising power, for example, 30VA for a 50VA transformer I just measured! This means that if you used two of these 50VA transformers back to back you would in fact only have 20VA of useful power available! It's therefore a good idea to stick to a smallish (12VA to 15VA say) transformer for the second one, and derate the first transformer by at least 5VA.

Last edited by daviddeakin; 15th Nov 2017 at 4:43 pm.
daviddeakin is offline