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Old 22nd February 2004, 02:27 AM   #1
pjb is offline pjb  United States
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Default toroid rewiring from 240v to 120v

Question: I have a toroidal transformer that is
in a British audio component (marked 240v) and
I want to use it in the USA.

The transformer looks to have 3 connections on
the primary side, 2 of which are used now in the
British wiring.

Anyone recognize this type of transformer? Any
safe way to determine what if any correct wiring
would make it run on 120v in the US?

Thanks!
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Old 22nd February 2004, 09:16 AM   #2
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Join Date: Jul 2003
Location: Newcastle, Australia
If it has three connections, then it is probably 240 and 220V taps. To enable 120V operation, you would need two separate primary windings (ie four connections).

Of course, you could still connect these to 120V anyway, but with half the output voltage (but still the same current rating, so therefore half the VA rating).

Cheers
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Old 22nd February 2004, 12:14 PM   #3
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Default Re: toroid rewiring from 240v to 120v

Quote:
Originally posted by pjb
Question: I have a toroidal transformer that is
in a British audio component (marked 240v) and
I want to use it in the USA.

The transformer looks to have 3 connections on
the primary side, 2 of which are used now in the
British wiring.

Anyone recognize this type of transformer? Any
safe way to determine what if any correct wiring
would make it run on 120v in the US?

Thanks!
Connect the secundary to say 12 V AC...and with the primary unconnected check the voltages between the 3 primary connections...

If they are equal then you have a 0-110 -220 primary!

PS:Atention to the voltages!!!
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Jorge
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Old 22nd February 2004, 01:28 PM   #4
sreten is offline sreten  United Kingdom
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Join Date: Nov 2003
Location: Brighton UK
Default Re: Re: toroid rewiring from 240v to 120v

Quote:
Originally posted by Tube_Dude

Connect the secundary to say 12 V AC...and with the primary unconnected check the voltages between the 3 primary connections...

If they are equal then you have a 0-110 -220 primary!

PS:Atention to the voltages!!!
IMO unlikely, but a simpler way of doing it is measuring the
DCR of the primaries, if equal = centre tap (why?), if one is
much smaller (10%) than the other then 220/240 taps.

sreten.
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