Using 120V transformers with 240V supply

Peter Daniel · 15th January 2003, 05:35 AM

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 · 15th January 2003, 06:50 AM

Linguistic battles aside...

Yes

I missed it too...

Paying for stupid mistake.

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

AudioFreak · 15th January 2003, 07:03 AM

That'll be fine Peter.

sangram · 15th January 2003, 07:13 AM

Quote:

Originally posted by AudioFreak
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 · 15th January 2003, 07:21 AM

Quote:

Originally posted by sangram
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 · 15th January 2003, 11:12 AM

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

Arne

jan.didden · 15th January 2003, 12:03 PM

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 · 15th January 2003, 12:33 PM

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 · 16th January 2003, 12:46 AM

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

blmn · 16th January 2003, 12:56 AM

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

15th January 2003, 12:03 PM	#7
jan.didden diyAudio Member Join Date: May 2002 Location: Great City of Turnhout, Belgium Blog Entries: 6	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.

15th January 2003, 12:33 PM	#8
Peter Daniel diyAudio Member Join Date: Jul 2002 Location: Toronto, Canada	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. __________________ www.audiosector.com “Do something really well. See how much time it takes. It might be a product, a work of art, who knows? Then give it away cheaply, just because you feel that it should not cost so much, even if it took a lot of time and expensive materials to make it.” - JC

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15th January 2003, 05:35 AM	#1
Peter Daniel diyAudio Member Join Date: Jul 2002 Location: Toronto, Canada	Using 120V transformers with 240V supply 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? __________________ www.audiosector.com “Do something really well. See how much time it takes. It might be a product, a work of art, who knows? Then give it away cheaply, just because you feel that it should not cost so much, even if it took a lot of time and expensive materials to make it.” - JC

15th January 2003, 06:50 AM	#2
sangram diyAudio Member Join Date: Sep 2002 Location: India	Linguistic battles aside... Yes I missed it too... Paying for stupid mistake. Great little idea about the auto (tranny, trafo, whatever)...

15th January 2003, 07:03 AM	#3
AudioFreak Warp Engineer On Holiday Join Date: Oct 2001 Location: Queensland, Australia	That'll be fine Peter.

15th January 2003, 11:12 AM	#6
yeti diyAudio Member Join Date: Nov 2001 Location: Ewersbach	It's easy, just wire the primaries in series and the secondaries in parallel, but check the sense of the windings! Arne

16th January 2003, 12:46 AM	#9
AudioFreak Warp Engineer On Holiday Join Date: Oct 2001 Location: Queensland, Australia	Not a good idea unless you can be sure that the VA drawn from both transformers are identical.

16th January 2003, 12:56 AM	#10
blmn diyAudio Member Join Date: Feb 2001 Location: .	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