I've done it in a pinch, and it worked for me, although I would be careful. I know in my application I didn't need much amperage.

Just to clarify I am talking about an actual transformer which looks something like this, and not something called a transformer that plugs into the wall but could contain other circuitry.

thanks Frank...but im talking about those yellow site ones commonly found in the uk...

regards

les

Why do you want do do this? 240VAC is more readily avaliable just about everywhere!

Yes. Transformers are the same one way as the other. The only thing to watch out for is the power (VA) rating of the transformer.

"Yes. Transformers are the same one way as the other. The only thing to watch out for is the power (VA) rating of the transformer."

thanks for the reply Bill,

can i assume then in a 3kw transformer (240 down to 110) it is the output quoted and stepping up i can input 3kw at 110 volts..(3000/110 =27.27 amps) and i will get 3kw (minus conversion losses) at 230volts and 12/13 amps...? sounds somewhere near right to me( but im the one asking the experts)...would be on a 13amp fuse ............to fill in the blanks ......., i was recently offered an american sine wave power inverter, and was thinking of how i could safely convert its output to UK voltage without too much expense and thought about putting its output through a much larger than reqd transformer to get it to 230/240 volts , if i use a larger capacity transformer then it wont be overloaded but the inverter output can still spike to its momentary rating, usually double the continuous rating....

asked the sparky at work but he gave me a funny look and said he'd never tried it.....

?????????

regards and thanks so far .....

aaaarrrggghhh tttuurrnnnn iiiittt ooooffffff hee hee

Your assumptions are correct. It's best to not operate the transformer at maximum, as this is typically determined by the temperature rise of the windings, which is a function of the wire size, magnetic efficiency of the core, etc. The limiting factor in transformers is the temperature at which insulation breaks down and causes faults between windings. A 3kVA transformer should not be wound secondary on top of primary, such as is the case in some small transformers, but would ordinarily be wound such that the primary and secondary winding are wound starting in close proximity to the core, resulting in similar efficiencies whether used as step-up or step-down transformer.

The ratio of this xfmr 2:1, and will work in reverse as well, as 1:2, but important facts are that whether it is a single phase or three phase xfmr, the line and load sides of the xfmr must be the same phasing.

yep , single phase .....

cheers for that ...

aaaarrrggg ttuuurrrrnnnnn iiiitttt oooooffffffffff hee hee

thanks for the advice fellas, im gonna give it a go,

regards

les

aaaarrrgggg ttuuuurnnnn iitt offffff hee hee

holy smoke you have gotten quite a response here, ok here is the low down on on the hooplah .

The 2:1 ratio is correct is correct as far as kva but you must keep in mind that the kva be in the lower portion of the equation. for example if a load at 110 VAC is supplied with with 220vac the load is that of of 1/2 of 230 VAC so if load is for example 5 amps at 110 VAC it is equal to 10.0 VAc at 230 VAC. so for a transformer in a boost application it would be load KVA times two times to give the most power requied for the load. however eighty percent is usually adequate.

Dave

Remember power in = power out.

"aaaaahhhh tttuuuurrrrnnnn iittt oooofffffff. hee hee"

Is that sound you are getting when you are working with transformer , i aan`t know that

Yes. Use of transformers is almost symmetric, but due to the losses it's not totally true. The 240 V output will be a bit lower.

Whoa horsey! Before we all go up in smoke....

I'm going back 20 years but I remember theoretically they are bi-directional, but practical transformers are optimised to work at maximum efficiency from primary to secondary; the primary coils are optimised to produce magnetic flux, and the seconary to intercept it (except toroidals which are rare due to the expense of winding them).

Thus when you reverse this process it will work, but at lower efficiency.

All OK until you used the magic words "3 kW" and "yellow boxes". Lets say the extra losses are 10% (I'm going to guess this is at least half the real losses). Now our little "box" has to get rid of up to an extra 300watts, on top of what it was originally designed for. Try touching a 300watt halogen lamp. That heat may do some sort of damage to the internal wiring.

By the by, the transformer output will be a socket (female) and the the input a plug (male). To use in reverse infers you will need a live plug from your 110 mains for the socket, and the units male terminals will be live @ 230. Earth continuity may also be an issue, as will volt drop. It might be very noisy too. What fun.

I'd use a 6kW unit to help get rid of the heat (which is a heavy beast) and preferably in someone elses property!