Using 120V transformers with 240V supply

[Peter Daniel]

I'm building PS to be used with 240V AC. However, the only transformers I have at my disposal are the ones specified for 120V. Can I use 2 transformers with their primaries in series and effectively used with 240V supply? Is it the same as using ea. transformer with 120V supply or am I missing something here?

 

[Sangram]

Linguistic battles aside...

Yes

I missed it too...

http://www.diyaudio.com/forums/showthread.php?s=&threadid=9398

Great little idea about the auto (tranny, trafo, whatever)...

 

[AudioFreak]

That'll be fine Peter.

 

[Sangram]

That'll be fine Peter.

Yeah but if you have varying loads on the two transformers you will have problems.

I am currently running the PM 665 with the two transformers in series. I will put in the auto transformer anyway as I don't want to blow anything to bits, ever...

 

[AudioFreak]

Yeah but if you have varying loads on the two transformers you will have problems.

True. I should have said.. As long as the total VA being drawn off the secondary side of each transformer is equal, it'll be fine.

To achieve that, assuming that both transformers are near to identical, you could run the secondaries of each transformer in parallel. ie. secondary winding #1 on transformer #1 in parallel with secondary winding #1 on transformer #2 and secondary winding #2 on transformer #1 in parallel with secondary winding #2 on transformer #2.

 

[yeti]

It's easy, just wire the primaries in series and the secondaries in parallel, but check the sense of the windings!

Arne

 

[jan.didden]

240v trannies

Peter,

It should work, but if the trannies are not completely identical (and half a winding secondary may be enough) you will connect in parallel two unequal voltage sources which will cause a relatively high circulating current heating up the tranny for no reason and robbing you of available power.

I would advice to check the loaded output of each secondary and if there is more than a few hundred mV difference, if that is an option, to use each secondary for one polarity of the supply.


Jan Didden

PS I forgot, but I had a similar case where I added one turn to one tranny to get them equal. May also be possible.

 

[Peter Daniel]

The transformers are identical and they have only one secondary ea. I was thinking about using each secondary for one polarity of the supply for the gainclone.

 

[AudioFreak]

Not a good idea unless you can be sure that the VA drawn from both transformers are identical.

 

[blmn]

Peter,

No problems if you're using the secondaries in series feeding the same amp(s) because (full wave ct schema to have v+ and v-, for example).

regards

 

[blmn]

You have to be aware of the secondaries phases, of course.

 

[EC8010]

Blumlein

You have to be aware of the secondaries phases, of course.

I see Blumlein is also your hero. What a loss!

 

[blmn]

Yes,

I had to choose a nickname to join to the forum. I chose some letters of Blumlein's name. After that, I found a picture of him on the Net. Very nice guy!