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AudioFreak 13th January 2002 02:37 AM

Wiring of a transformer
I've got an old EI core transformer with dual primaries (115/230V) with and a multi-tapped secondary with 5 wires.

What i need to know is this .... when i go to wire the primaries in series, how can i tell the beginning of a winding from the end of a winding?

norman 13th January 2002 03:50 AM

Your question makes no sense. What's the difference between the beginning and the end? A piece of wire has 2 ends. It seems to me they look the same.


AudioFreak 13th January 2002 03:54 AM

with a transformer there is a 'beginning' and an 'end' to each winding .... the idea is that you wire the end of the 1st winding to the beginning of the second winding.

subwo1 13th January 2002 03:56 AM

One way is to hook the primaries up to a small transformer's secondary. First check the primary windings with an ohm meter to tell which leads go to each primary. The small one can have a secondary rating of 12V, say. Then guess, and connect the primaries together. When you hook them to the small transformer, the one under test should not draw much current or load the 12V one. Otherwise, reverse one of the primaries.

You can also use a short lamp instead of the 12V transformer. If you get the connections wrong, the light will glow at full brightness. You can use a 60 or 100 watt light bulb to do the test.

Lisandro_P 13th January 2002 08:26 AM

You can wire the secondaries in series and check the voltage with a multimeter; if they're out of phase, the voltage will be low (zero if they're identical).

AudioFreak 13th January 2002 11:14 AM

thanks ... Lisandro_P, its the primaries i am concerned about not the secondaries.

blmn 13th January 2002 12:05 PM


I think you can put the secondaries (identicals) in paralel, applying a 60Hz signal from an generator and, with an scope, see the phase of the signal at the primaries. When tey are the same you can use it has a relative "beginnings" and "ends" for both sides of the transformers. Make it at opposite way works too, but, It's hard to setup and you must use more voltage.


AudioFreak 13th January 2002 12:25 PM

thanks blmn i hadnt thought about that .... i'll try both methods and see what data i can gather.

PassFan 13th January 2002 02:51 PM

I know if you wire it wrong on a toroid the two fields oppose each other and produce enough demand to blow the 120v fuse protection. I'm not sure on an E-core. Yes, the voice of experience, the worlds fastest teacher.:)

AudioFreak 13th January 2002 02:53 PM

Yeah i agree PassFan,

Experience is the best although it might be painful gaining it :)

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