US RV 230-110-230 transformer

[nozspark]

Hi,
I have just been asked to convert a recently imported RV to 230v.

What I am planning on doing is to leave the existing 110v stuff alone and to add a transformer & change over switch so that it can be plugged into a UK campsite supply (16A ceeform) - I will also be adding a 230v cu and appropiate RCD & MCB's to power a couple of additional 230v sockets - I also want to retain the use of the 110v genny.

Before anyone starts I have had a look through this site and the internet in general over the last few hours; and appart from
//www.diynot.com/forums/viewtopic.php?p=515108#515108 I have drawn a blank.

I have also been in touch with a transformer manufacturer (via a local wholesaler) who want to supply me with a dual winding tx (one winding step up, the other step down) but I am still waiting on a price.

So, to my question:-

Has anyone on here done anything like this before?

If so any hints, tips and sources of parts & information would be very much appreciated.

Cheers in advance

 

[bernardgreen]

You must consider the effect of running USA equipment that is designed for 60Hz on a UK supply of 50 Hz. Induction motors will run slower but take more current ( impedance of coils is lower at 50Hz than it is at 60Hz ).

Tranformers in power supplies may be prone to running warmer for the same reason.

Remember that USA appliance wiring has BLACK as LIVE and WHITE as NEUTRAL

 

[nozspark]

Just been quoted £300 + VAT for the transformer in a wall mounted enclosure, just wondering if anyone knows of any other suppliers.

As this is going in a motorhome I don't think there will be any frequency concious appliances..

 

[ColJack]

stick this in a cupboard, hardwire the output to the 110 stuff ( take off the 3/4 sockets on it.. ) and the input to the 240 you install..

 

[bernardgreen]

http://www.sigaelec.co.uk/

make custom and standard transformers. Laminated up to 5Kva and toriodals up to 10Kva

The standard toroidal power transformer range is suitable for all normal transformer applications and covers a range of power outputs from 1VA upto 10KVA when operated from a 50Hz power supply. Transformers can also be supplied for use on 60Hz and 400 Hz supplies.

 

[nozspark]

Bernard,
I've just had a reply from them and "We regret this item is not within our normal manufacturing range" so I am still looking for a supplier for this transformer.

 

[plugwash]

I don't see any reason you need a special transformer, an ordinary site transformer should work fine once the connections are modified appropirately.

 

[djrichie_t]

I don't see any reason you need a special transformer, an ordinary site transformer should work fine once the connections are modified appropirately.

Site transformers are only designed for 'intermittent use' and are very cheaply made, they do get hot.

Best transformer to use is a toroidal single wound autotransformer. Check these out, they are made to a very good quality.

 

[nozspark]

Cheers,

Have sent them a query, am only looking a 3kva so I hope their US3010 will do the trick!

 

[ban-all-sheds]

As this is going in a motorhome I don't think there will be any frequency concious appliances..

Motors in fridge/freezers?

Motors in a/c units?

Motors in microwave ovens (turntable)?

Motors in waste-disposal units?

Motors in toilet macerators?

Motors in central vacuum cleaning units?

OK - some of these only run very intermittently, so the heating effect won't matter, but others run for longer periods - you should probably think about replacing the a/c.

 

[nozspark]

I know for a fact that the owner will not replace the A/C unit, so I will either have to isolate that circuit in the change over switch (when on shore power), disconnect it or just put a big label in the RV. As for the other things, I feel that the effect would be minimal.

 

[ban-all-sheds]

They won't thank you for disabling the a/c if they're trying to sleep in the vehicle in summer...

Seriously - check with an automotive a/c specialist - your customers really need to be aware of the implications of running it on a 50Hz supply, as these could be serious, and ignoring any potential problems won't make them go away.

 

[Stoday]

Most small motors have "universal" windings with a wound rotor in series with field windings. Such motors work from DC upwards and include macerators, waste disposal units and the like.

The problem arises with induction motors. First, there is a 17% fall in speed when running a 60Hz motor on 50Hz mains. Second, the magnetic field is induced for 17% longer time, which starts to saturate the iron. Iron losses increase dramatically and can lead to overheating. On the other hand running a 50Hz motor at 60Hz does not result in greater iron losses. The 20% speed increase might increase the load on the motor, increasing the slip and thus increasing rotor losses. So it can result in overheating for an entirely different reason.

Air conditioning is the biggest problem because it incorporates a large induction motor. This was more of a problem in the UK because unlike the US and Europe, households with three phase supplies are very unusual. The starting current of a large single phase induction motor will cause lights to flicker. This is no longer true for better quality air conditioners, which are driven through an invertor. The purpose of the invertor is to minimise the starting transient. Also, it is possible for some invertors to run on 50Hz or 60Hz supplies, so the right choice of air conditioner could solve this problem.