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Old 18th May 2006, 06:08 AM   #1
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Default Rewinding 220v transformers for 110v?

I've got some excellent 220v transformers for my GC project; each is rated for 48VCT. I'm now using two of them in series, producing 48vct total on 110v. Each is rated 330VA on 220v; half this is likely plenty.
Does anyone know a good way I could possibly convert one of these into a 110v transformer? Perhaps the center could be found on the primary, and it could be converted into dual primaries?

Sorry to ask the stupid question, but these things weigh over 20 lbs. each. They're ridiculously heavy.
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Old 18th May 2006, 07:20 AM   #2
rpapps is offline rpapps  Antarctica
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Hi
The problem you face is that the primary is usually wound first and the secondary wound over the top. So you would have to strip it off first and then rewind the whole thing to achieve what you want.
Alternatively, if you have three phase power in your house and don't mind installing a special outlet just for your amp, hooking it between any two phases will give you 220 volts.
Cheers
Rob
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Old 18th May 2006, 07:50 AM   #3
AndrewT is offline AndrewT  Scotland
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Hi,
three phase will give you root(3) times the single phase voltage.
120Vac>=208Vac, 110Vac>=190Vac.

I wonder if the poster meant looking for the two poles that exist in some (many) US homes. These are 180 degrees out of phase and will give 2times the voltage.

Using the series method reduces the VA rating of each transformer drastically, possibly half.
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Old 18th May 2006, 07:59 AM   #4
rpapps is offline rpapps  Antarctica
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Quite right Andrew.
Sloppy math on my part.
Cheers
Rob
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Old 22nd May 2006, 07:54 AM   #5
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Well, I now feel very confused.
That said, that's nothing outside the ordinary.

Anyway, the primary seems to be seperate from the secondary; it's an EI-core transformer. What if I were to simply scratch off (and replace) bits of insulation on the primary winding until I found a center tap, then cut the wire in half, creating two seperate 110v primaries to be wound in paralell?

Also, how would I go about finding these out-of-sync leads? I don't even think my house has three-phase; the house is over 70 years old.
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Old 22nd May 2006, 08:48 AM   #6
AndrewT is offline AndrewT  Scotland
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Hi Spasticteapot,
from what I have managed to glean from this forum you do not have 3phase into domestic properties in the US.

It appears that all have single phase 110Vac and many have 2phase 220Vac (110Vac,110Vac from ground).

Some have referred to a high power connection in the basement or adjacent to the meter/distribution board.
This high power connection seems to be both phases brought to a socket that makes 220Vac available.

What have you got?

Just to clarify (or muddy), in the UK a few domestic properties have 3phase (415Vac;- 240Vac to ground times three) available or two poles of a 3phase supply.
There may be the rare equivalent to this in the US.
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