110v Transformers for 240v

Puffin · 18th April 2008, 04:15 PM

Can anyone suggest a wiring diagram to connect two 110v trannys to get 220/240v ?

martin clark · 18th April 2008, 07:05 PM

What is it you need to do?

Jut connecting two 110v secondaries in series will get you in the area for many purposes, but that may not be enough if you need a full240v from 110v input - the step-up configuration will tend to exaggerate the apparant voltage drop under load.

Puffin · 18th April 2008, 07:23 PM

The 110v are the primary's.

martin clark · 18th April 2008, 07:35 PM

OK, but is it 240v input, and 240v output you want, or what combination..?

If you mean 110v primary:110v secondary transformers - you could connect two transformers with both primaries in series and two secondaries in series, and apply 240v to get a 240v:240V composite transformer, but it's not a good idea on the whole.

Puffin · 18th April 2008, 07:37 PM

What I am trying to achieve is 240v input by using two 110v transformers. the ac output is immaterial at present.

martin clark · 18th April 2008, 07:44 PM

Then just connect the two primary -side windings in series. You can leave al teh secondaries uncommitted.

Don't expect this to be very useful. Use a minimum-value mains fuse etc. Assuming good matching, these transformers will be seeing 120VAc each, but it's not guaranteed: if wildly different in VA capacity, the smallermay be exposed to even higher voltages . Even more seriously, if they are wound for 60Hz (US etc) mains, the cores will be under-sized for use in the UK anywhere near rated capacity, and I would expect them likely to hum badly. HTH!

Spiny · 18th April 2008, 07:48 PM

the problem IMO is that having transformers in series they must supply the same power otherwise you will get an inbalance between the transformers and the output voltages will vary.
I suggest you use one with the correct primary or use a 230/110 autotransformer to drive the 110 devices in parallel.

18th April 2008, 04:15 PM	#1
Puffin diyAudio Member Join Date: Feb 2006 Location: U.K	110v Transformers for 240v Can anyone suggest a wiring diagram to connect two 110v trannys to get 220/240v ?

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18th April 2008, 07:05 PM	#2
martin clark diyAudio Member Join Date: Jul 2003 Location: Bath, UK	What is it you need to do? Jut connecting two 110v secondaries in series will get you in the area for many purposes, but that may not be enough if you need a full240v from 110v input - the step-up configuration will tend to exaggerate the apparant voltage drop under load.

18th April 2008, 07:23 PM	#3
Puffin diyAudio Member Join Date: Feb 2006 Location: U.K	The 110v are the primary's.

18th April 2008, 07:35 PM	#4
martin clark diyAudio Member Join Date: Jul 2003 Location: Bath, UK	OK, but is it 240v input, and 240v output you want, or what combination..? If you mean 110v primary:110v secondary transformers - you could connect two transformers with both primaries in series and two secondaries in series, and apply 240v to get a 240v:240V composite transformer, but it's not a good idea on the whole.

18th April 2008, 07:37 PM	#5
Puffin diyAudio Member Join Date: Feb 2006 Location: U.K	What I am trying to achieve is 240v input by using two 110v transformers. the ac output is immaterial at present.

18th April 2008, 07:44 PM	#6
martin clark diyAudio Member Join Date: Jul 2003 Location: Bath, UK	Then just connect the two primary -side windings in series. You can leave al teh secondaries uncommitted. Don't expect this to be very useful. Use a minimum-value mains fuse etc. Assuming good matching, these transformers will be seeing 120VAc each, but it's not guaranteed: if wildly different in VA capacity, the smallermay be exposed to even higher voltages . Even more seriously, if they are wound for 60Hz (US etc) mains, the cores will be under-sized for use in the UK anywhere near rated capacity, and I would expect them likely to hum badly. HTH!

18th April 2008, 07:48 PM	#7
Spiny diyAudio Member Join Date: Feb 2008	the problem IMO is that having transformers in series they must supply the same power otherwise you will get an inbalance between the transformers and the output voltages will vary. I suggest you use one with the correct primary or use a 230/110 autotransformer to drive the 110 devices in parallel.

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