transformer for America

[Pagetslady]

Here is an unusual question, I have a yellow 240v to 110v transformer for working on site, but I am visiting USA soon where they have 110v if I put 110v from shore power into the 110v socket will I get 240v out of the 240v socket.

 

[misterg]

Here is an unusual question, I have a yellow 240v to 110v transformer for working on site, but I am visiting USA soon where they have 110v if I put 110v from shore power into the 110v socket will I get 240v out of the 240v socket.

Yes.

Andy

 

[nedmin]

Dont forget they have 60 cycles/second ac over there not 50. as previously said will give you 240v but depends what you want to run off it.

 

[sarabande]

it also depends if the unit is fitted with control diodes and/ or RCD internally.

What's the make please?

 

[Ubergeekian]

Don't do it!

Here is an unusual question, I have a yellow 240v to 110v transformer for working on site, but I am visiting USA soon where they have 110v if I put 110v from shore power into the 110v socket will I get 240v out of the 240v socket.

I doubt this will work, and it could be extremely dangerous. Here's why.

The 110V secondary side of site transformers is centre tapped to earth, making it a 55-0-55 supply, with the two 55s 180 degrees out of phase. That's for safety - 55V can hurt a fair bit but is extremely unlikely to kill you, unlike 110V or 240V.

What you're proposing would put US live-and-neutral 110V across the two outer tappings. What happens then depends on the earthing arrangements of the supply.

• If the neutral is locally bonded to earth, one half of the input windings would effectively be shorted, with 110V across the other half. That will cheerfully induce something in the secondary - but it will also attempt to induce anything up to 110V in the other half of the primary. The effectively short-circuited other half of the primary. If you're lucky it'll just blow a fuse.
• If the neutral is floating you'll try to pull it up to 110V or thereabouts. This will not be good, to put it mildly, since it will be at 110V out of phase with the supply, so you'll be simultaneously encouraging every load on the same supply (a) to quadruple its power draw and (b) take half of that power through the primary of your transformer. If you're lucky, you'll just blow a fuse. If you're unlucky you'll damage some or all of the other loads on the circuit, blow up the transformer and electrocute your neighbours.

Use the proper transformer for this.

Note: what precisely happens in either of the above cases depends on details of the transformer windings. It won't be pretty, though.

 

[mikefleetwood]

I was under the impression that the American 110V supply was already centred on ground/earth, to give maximum 55V on either wire for exactly the reasons explained above.

Also, I thought the 110V on site transformers was isolated from earth.

Perhaps someone with accurate information could tell us.

However, to answer the original question if you put 110V into the 110V "output" you will get 230V from the "input" - probably. But, both connectors will be reversed, putting live volts on the exposed pins, so very dangerous! Also, you will not get the same VA power rating as if used "right way round", as the new primary will have the wrong number of turns to drive the core without saturation (if I remember the basic theory correctly!).

 

[NormanS]

Here is an unusual question, I have a yellow 240v to 110v transformer for working on site, but I am visiting USA soon where they have 110v if I put 110v from shore power into the 110v socket will I get 240v out of the 240v socket.

Presumably your present transformer is required because at least some of your equipment is 110v. Why do you want to use 240v in USA?

 

[VicS]

I think you will find that 110volt site transformers do have a centre tapped secondary
see HERE
for an example, making it a 55-0-55 supply.


AFAIK the public electricity supply in the US is not similarly 55-0-55 but has one conductor grounded.
If this is so one half of the 110volt winding will be shorted out by the two earth connections unless the local earth( ground) is not connected to the centre tap.
Even then the earth on the 240 volt side will still be connected to the centre tap of the 110volt winding and will therefore be at 55 volts relative to the local earth so that internal connection will have to be broken and remade to the supply ground conductor

The point about male and female sockets and plugs is a safety issue.

It possible maybe with some modifications to the way the transformer is wired and the type of connectors.

The best advice you can be given I think is to get the proper equipment for the job.

 

[mikefleetwood]

The best advice you can be given I think is to get the proper equipment for the job.

Second that.

 

[Ubergeekian]

AFAIK the public electricity supply in the US is not similarly 55-0-55 but has one conductor grounded.

The public supply in the US is generally 110-0-110 two phase, using 110V for sockets and the full 220V for big wired-in stuff like cookers.

 

[VicS]

The public supply in the US is generally 110-0-110 two phase, using 110V for sockets and the full 220V for big wired-in stuff like cookers.

The 110-0-110 two phase being the 220volt supply centre tapped ?

If so that means the 220volt supply is CTE ?

 

[misterg]

FFS!

You would need to connect it up properly, but it would work fine. You wouldn't connect an earth to the 110V winding if it was the primary (WTF would you??), and you would need to make the correct arrangements for establishing a neutral and "earth" connection on the 240V side.

That said, if you don't understand it, don't do it.

Andy

 

[Ubergeekian]

You would need to connect it up properly, but it would work fine. You wouldn't connect an earth to the 110V winding if it was the primary (WTF would you??)

Dunno about you, but I rather like earth connections on mains voltage systems. And if you have an earth connection, the centre of the 110V side will be earthed, which as two of us have now pointed out is a Very Bad Thing Indeed.

Of course you could delve into the works of the thing, cut off the earth and so on, but at that level of fiddling you might as well make the right thing in the first place.

 

[Ubergeekian]

The 110-0-110 two phase being the 220volt supply centre tapped ?

If so that means the 220volt supply is CTE ?

It's a two-phase system, so you have a common neutral and two 110V lines 180 degrees apart. Occasionally people try to draw extra current by wiring supplies from different rooms in parallel. If they are on opposite phases, this can be a bit unfortunate.

 

[oldharry]

Why risk it? Get one of these: http://www.maplin.co.uk/Module.aspx?ModuleNo=24488

 

[RobHom]

Second that.

I will "second" your "second"....and here's why: I have been in marinas here in the states where the electric service has not been quite "kosher"...in that whomever did the wiring was not all that good at it...or there had been excessively high tides that leaked into the conduit piping and caused some "shorts" and other problems....and also have seen where the hot and neutral lines have been reversed and even where the ground was placed wrong....and it was basically "out of phase"....

You won't have a problem in a newer marina...but in older ones that have had repairs done by "their" maintenance people the possibility exists that they may not have been "licensed electricians".....

Best to have the right stuff to begin with.