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#1 Toroid Secondary Connections

Posted: Tue Sep 07, 2021 7:59 am
by Ray P
I have a Canterbury Windings' toroidal transformer which has two 0-15VAC secondary windings.

Image

Black-White is one secondary and Red=Yellow the other.

I need a 30VAC supply so plan to connect the two secondary wingings in series, th problem is that the transformer isn't labelled so I don't know which is the 'start' and 'end' of each secondary - My starting assumption is that there is a sequence so for 30VAC I would the black and yellow wires and join the White and Red for series use however, that is just an assumption and if I make those connctions and measure it I'll either get 30VAC or something like 0VAC and a lot of heat. I'm seeking advice on resolving this conundrum without doing any damage.

Ta

#2 Re: Toroid Secondary Connections

Posted: Tue Sep 07, 2021 8:27 am
by jack
Start by connecting them in series - you'll either get approximately 0V or 30VAC as you say.

No damage will be caused; you won't get heat.

If you get 0V, they are in anti-phase, i.e. the joint is the same end of each winding; if you get 30V then they are in phase and the joint is opposite ends of each winding....

#3 Re: Toroid Secondary Connections

Posted: Tue Sep 07, 2021 8:48 am
by Nick
My guess is that black and orange are the same phase, so join white and orange and measure across black and yellow.

#4 Re: Toroid Secondary Connections

Posted: Tue Sep 07, 2021 1:00 pm
by Ray P
Thanks Gents, I'll try it later.

Looks like red is the new orange for me!

#5 Re: Toroid Secondary Connections

Posted: Tue Sep 07, 2021 7:00 pm
by Ray P
Yep, that was right, cconnected red and white and I measure 33VAC across the yellow and black, obviously with no load so circa 10% regulation it would seem.

Its a 300VA toroid so 30VAC @ 10amps will do nicely for a stereo class A SIT amplifier with circa 2A standing current.