Alfamag Toroidal Transfo: not sure how to wire

michouthefirst · 9th November 2012, 12:40 PM

I bought this transfo and I am not sure how to wire it. PC Mountable Toroidal Transformers | Low Profile PC Mount Transformers : AlfaMag Electronics

If you look at the PDF file linked there http://www.alfamag.com/assets/files/...ansformers.pdf

It looks like there is 4 windings on the transfo. I was expecting one for primary and another one, center tapped, secondary. Now there seems to be 2 primaries and 2 secondaries.

When I ordered it, I choose single primary, single center-tapped secondary.

Could anyone help me with this?

Thank you.

mickeymoose · 9th November 2012, 01:48 PM

Prim 115VAC: 1 to 3 = AC Line, and 2 to 4 = AC Return or Neutral
Sec. CT: 8 = AC, 7 to 6 = CT, 5 = AC

michouthefirst · 9th November 2012, 01:57 PM

Ok, cool. So both primaries must be connected for the transformer to work properly?

Are all toroidal transfomers wired that way?

And thank you more the info

AndrewT · 9th November 2012, 02:22 PM

A dual 115Vac primary can be wired for either 115Vac duty or for 230Vac duty.
For 230Vac, the two primaries must be wired in series. Use a bulb tester to ensure no accidents due to incorrect phasing.
For 115Va, the two primaries should be wired in parallel, again use a bulb tester to avoid phase error accidents.
But a single 115Vac primary connected to 115Vac and one unconnected 115Vac primary will work. It works very well but has only half the VA capability of the dual primary version, half the ampere-turns.
But be careful, the unconnected primary has 115Vac at it's ends !!!!! and that "loose" primary is not properly isolated from the mains. There are only two thin layers of enamel between the mains and the loose ends !!!!!

michouthefirst · 9th November 2012, 02:30 PM

I will just wire the 2 primaries in parallel then. Thanks!

9th November 2012, 12:40 PM	#1
michouthefirst diyAudio Member Join Date: Jul 2012 Location: Gatineau	Alfamag Toroidal Transfo: not sure how to wire I bought this transfo and I am not sure how to wire it. PC Mountable Toroidal Transformers \| Low Profile PC Mount Transformers : AlfaMag Electronics If you look at the PDF file linked there http://www.alfamag.com/assets/files/...ansformers.pdf It looks like there is 4 windings on the transfo. I was expecting one for primary and another one, center tapped, secondary. Now there seems to be 2 primaries and 2 secondaries. When I ordered it, I choose single primary, single center-tapped secondary. Could anyone help me with this? Thank you.

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9th November 2012, 01:48 PM	#2
mickeymoose diyAudio Member Join Date: Nov 2008	Prim 115VAC: 1 to 3 = AC Line, and 2 to 4 = AC Return or Neutral Sec. CT: 8 = AC, 7 to 6 = CT, 5 = AC

9th November 2012, 01:57 PM	#3
michouthefirst diyAudio Member Join Date: Jul 2012 Location: Gatineau	Ok, cool. So both primaries must be connected for the transformer to work properly? Are all toroidal transfomers wired that way? And thank you more the info

9th November 2012, 02:22 PM	#4
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	A dual 115Vac primary can be wired for either 115Vac duty or for 230Vac duty. For 230Vac, the two primaries must be wired in series. Use a bulb tester to ensure no accidents due to incorrect phasing. For 115Va, the two primaries should be wired in parallel, again use a bulb tester to avoid phase error accidents. But a single 115Vac primary connected to 115Vac and one unconnected 115Vac primary will work. It works very well but has only half the VA capability of the dual primary version, half the ampere-turns. But be careful, the unconnected primary has 115Vac at it's ends !!!!! and that "loose" primary is not properly isolated from the mains. There are only two thin layers of enamel between the mains and the loose ends !!!!!

9th November 2012, 02:30 PM	#5
michouthefirst diyAudio Member Join Date: Jul 2012 Location: Gatineau	I will just wire the 2 primaries in parallel then. Thanks!