Transformer with center tapped primary

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I bought a transformer from eBay fully expecting 2x115v primary windings that I could wire in parallel for 115v or series for 230v. Instead the transformer is wound as 0-115v-230v with 115v as a center tap. I’m sure it’s fine wired for 230v however I have 115v mains and using the tap leaves the winding unused.

So would it be okay to use this type of transformer at 115v?
 
To be certain you should measure winding resistance.
Since transformer is expected to put out same power either on 115V or 220V , then 0>115 winding must use thicker wire (and have lower resistance) than to 115>230V one.
So measure both.
No need for an accurate value here, just to make a comparison and confirm/deny this possibility.
So maybe your transformer is, say, 3 ohms 0>115, 5 or 6 ohms 115>230 and 8 or 9 ohms 0>230 taps.

Please measure and post results.
 
fine, you can use it.
In the old days, International transformers were multitapped and each section was wound with the proper diameter wire, period.
Look at this VOX guitar amplifier (used by Beatles, Stones and Queen among 1000 others)
To work *anywhere* on the World it had primary taps at: 115/160/205/225/245V.
ac301960.jpg


Then cutthroat competition chimed in and transformers became dual series/parallel primary, matching only 2 voltages and "sort of" close enough to others.

Of course, saving some 20% weight and cost ;)

Unused windings are he norm there and well accounted for.
 
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