Using UK equipment in USA

A common arrangement, I believe, is for a transformer to have 2 sets of primary windings, which are used in series or in parallel, to suit the mains voltage. This could be done by rewiring instead, clearly - rather than by an external switch,

Japan - bizarrely uses 100V AC - but is both 50Hz & 60Hz....!  (50Hz in Tokyo & north - 60Hz in Osaka and south)

Based on my experience with AC power in aerospace, it was usually the low frequencies which were the most difficult - and would set the design point for a transformer, it seemed. Higher frequencies were easier to deal with.

Clearly all this is a pain to makers - which is why SMPS's are so attractive - 100V to 240V input, without any change. 

If tge US "240v" is indeed from a centre tapped transformer providing two 120v RMS circuits (each using the centre tap as neutral, which will be approximately at ground potential as is the UK neutral, then taking the supply from the two 120v live ("hot") wires and ignoring the neutral will indeed give 240v RMS.

Any 240v rated transformer should work satisfactorily (with reference to earlier discusdions on frequency), but there is a potential safety issue:- both supply wires are live, at 120v above ground, whereas in UK only one is. Once through the transformer it is irrelevant, but it means that if there is a single fuse, on only what in UK would be the live feed in the equipment, that would not cut off the other 120v live feed from the switch and transformer primary etc. i am not saying this is necessarily a dangerous situation, however protection then is wholly reliant on any fuses or breakers in the second live feed outside the equipment. It seems a less safe way of providing 240V than ours. 

joerand posted:

David O,

Are you moving into your own property in the US?  If so, I would give serious consideration to having a dedicated 240-volt circuit installed in your listening room. US mains panels almost always have additional vacant breaker positions and it's a simple matter of fitting a 2-pole breaker to get a 240-volt circuit. Easy job for a qualified electrician and very likely cheaper than voltage converting your three boxes.

Most US homes already have existing 240-volt circuits for electric clothes dryers, stoves and ranges, and sometimes 240-volts circuits in the garage for compressors or welders, so it's nothing unusual.

In your case then it's just a matter of having a UK socket (which you may have to order yourself) installed at the end of your dedicated 240-volt circuit.

And if someday you move back to the UK, take your unconverted Naim boxes right back with you.

Whilst this will work I would be very wary of fitting UK plugs/sockets in an American home. As I understand it the US insurance companies take a dim view of paying out in the event of a fire if the equipment is not connected with connecters that have been tested by UL. If you are going to use a US 220V supply I would suggest you have a dedicated US socket and plug for this which will be covered on the insurance. I appreciate its a low risk, but in my view its not one worth taking.

Innocent Bystander posted:

..., if the US so-called "240v" is actually derived from two phases 120° out of phase (as in 2 phases of a 3 phase generated supply), each of 120v RMS, then the voltage of the combined supply is actually 208v RMS, not 240v at all. 

Yes, that's exactly what it is. The square root of 3 is your friend. If I recall correctly, we had a 'healthy' 120v at our home.

Mike-B posted:

Allante93 posted:

Most countries use 50Hz (50 Hertz or 50 cycles per second) as their AC frequency. Only a handful use 60Hz. The standard in the United States is 120V and 60Hz AC electricity.Mar 26, 2017"

What are the Advantages, or Disadvantages? 

  its a friggin' nuisance for manufacturers,  but It is what it is & in use it has niether pros or cons.    However higher voltage like 230v (vs 120v) means power cables can be aprx 50% smaller diameter to carry same wattage & similar for switch & power outlet ratings.   So higher voltage has potentially a small cost saving for the consumer,  but in practice its not really applicable as each country has its own set of domestic regulations that don't really allow comparison.        

""Of the over 200 countries listed below, most use 220-240 VAC. Others use between 100-120VAC.

{Some countries, including the United States, use dual voltages. 43 countries use 60Hz, while the rest 50Hz.}

United Kingdom
230/240V 50Hz

United Arab Emirates
220V 50Hz

=====================

Saudi Arabia
127/220V 60 Hz

United States
120/240V 60Hz""

Just viewing some numbers, to see if any political relationships exist!

As you say Mike, it is what it is!

Thanks Mike!

Allante93!

Isn't 110v less likelty to kill than 240v. A definite pro

Richard Dane posted:

Allante,

the answer to your question re. the transformers is that some are the same and some aren't - it depends on the model in question.  Some will be dedicated to a particular voltage (IIRC the i series introduced this), others will be re-wirable to work on either 230V/50Hz or 115V/60Hz.  I don't know exactly which is which these days as it's been some years since I took note of these things from when I was working at the factory, however,

{{a quick question to Steve Hopkins at Naim for any particular unit should give you a prompt answer.}}

Of course, the transformer tolerances allow so that they can usually run 210-250V and 100-130V respectively.  And anecdotal evidence suggests that in parts of rural Australia voltages over 250V have been recorded and the transformers have seemingly coped Ok with that as well.

Thanks Richard!

I love the Forum, very informative.

But this really hits home!

In the Market for a SC 2!

A couple of Authorized Dealers, suggest it was ok, by letting me know, they could have it converted from 230 to 115.

But as you say Richard, a simple call would verify if Naim used the same transformers, in their SC 2008 -2012 models.

UK vs US versions 230 vs 115

Allante93!

PS. Thanks Simom in Sulfolk:

"Critically a transformer supporting 50Hz will be larger and more expensive than one solely supporting 60Hz - and a 60Hz transformer might run slightly warmer than a 50Hz due to eddy current inefficiencies... however looking at my local toroidal transformer catalogue it is minimum frequencies that are stated and essentially I saw  a choice of between 48Hz or 50Hz minimum supporting most of the global mains voltages - so

{{I suspect the Naim transformers will be fine at 60Hz with them having a minimum frequency of 50Hz. But again easily dealt with with a quick call to Naim customer care"}}

fatcat posted:

Isn't 110v less likelty to kill than 240v. A definite pro

This might be more an urban myth ... but I recall my physic teacher saying 110v is less likely to kill than 240v ... but 60Hz is more likely to kill than 50Hz and by a greater margin (and so 230v 50Hz is "safer" than 110v 60Hz).

. LIke being hit on the head by a smaller hammer, but mor frequently.

Allante93 posted:

A couple of Authorized Dealers, suggest it was ok, by letting me know, they could have it converted from 230 to 115.

Not 100% certain, but converting from 230v to 110v will effectively reduce the number of primary windings by half. Surely this is effectively the same as using a transformer that is half the size. Probably not a good thing.

 Although I could be wrong.

Allante93,    240v in USA is not a standard single phase utility supply.   It can be found by using 2 phases off the standard 220/240V 3 phase domestic neighbourhood supply giving 220/240 across  2 phases with a centre tap neutral & is normally used for high power consumption equipment in domestic installations such as AC.  An alternative is via a transformer for 1-Phase 2-Wire 120-Earth-120 = 240V (No neutral)

USA electricity is a bit of a mess compared to the simple European stnds,  3 phase comes from star (called wye in USA) & delta transformers.   3 phase voltages can be 240V & 400/480V & even 600V to local distribution systems & industrial users.  With a delta transformer a centre tapped winding can give yet another higher voltage on one leg & is know as 'high leg' voltage  

fatcat posted:

Isn't 110v less likelty to kill than 240v. A definite pro

Hmm - I looked it up to see if that is the case as it is generally  current that is the killer not voltage ... (lower voltage equals higher current for a given power)

So comparing electrocution stats (electrocutions per million) in different countries - the US seems to be ahead of  Europe - so that tends to imply that 110volts is more dangerous - but I suspect its more cultural and environmental rather than voltage and current and also there is a view there is increased complacency with 110volts where as most respect 220volts. There is also a anecdotal view that 110volts is more likely to cause building fires in fault situations than 220volts but I cant find any data to back that up

S

Simon-in-Suffolk posted:

fatcat posted:

Isn't 110v less likelty to kill than 240v. A definite pro

Hmm - I looked it up to see if that is the case as it is generally  current that is the killer not voltage ... (lower voltage equals higher current for a given power)

So comparing electrocution stats (electrocutions per million) in different countries - the US seems to be ahead of  Europe - so that tends to imply that 110volts is more dangerous - but I suspect its more cultural and environmental rather than voltage and current and also there is a view there is increased complacency with 110volts where as most respect 220volts. There is also a anecdotal view that 110volts is more likely to cause building fires in fault situations than 220volts but I cant find any data to back that up

S

I seem to recall reading somewhere a long time ago that there were quite a few 'incidents' when electricians from the US were working in Germany rewiring things after WW-II. I dunno if it's true or not but it seems credible. I do know from personal experience that 230v hurts more than 115v because I've tried both, although grounding and other conditions were not constant 

Got it I can now see why some devices designed for the European supply could not be used on the US 240 volt circuit.... In the UK and I believe the rest of Europe we use one live wire wire and one neutral for 230 volts. The neutral is low impedance to ground... some transformers are designed that the primary is live and the neutral and ground are closely linked and have a limited potential difference between them. However in the US the 240 volt system uses two 180 degrees out of phase 120 volt lines - to give the the 240 volts (which is RMS) - think balanced interconnects. But crucially neither voltage line is closely related to earth - in fact each one has a 208 RMS volts compared  to earth - thanks Mike for the diagram. Therefore if a transformer or perhaps more typically a device relied on earth and neutral to be close to each other damage could result.

Sooo given all this I am not sure I would recommend using the high power US 240 volt distribution system for a regular consumer device unless the manufacturer has specifically cleared it. The 60Hz/50Hz thing was a red herring.

S

 Simon,   two phases from three  are 120 degrees out of phase with each other   (360/3)    

Doesn't ohms law state the higher the voltage, the higher the current, given resistance is constant.

Also, for safety reasons, 240v power tools are not permitted on construction sites.

Mike, yes in a regular European 3 phase system. The US high power distribution system that I believe is now installed in all new buildings in the US  uses L1 and L3 which are 180 degrees out of phase of each other as per your diagram  i.e. L1 and L3 balanced around a centre ground.

fatcat posted:

Allante93 posted:

A couple of Authorized Dealers, suggest it was ok, by letting me know, they could have it converted from 230 to 115.

Not 100% certain, but converting from 230v to 110v will effectively reduce the number of primary windings by half. Surely this is effectively the same as using a transformer that is half the size. Probably not a good thing.

 Although I could be wrong.

No, half the voltage means twice the current for the wame power, so wire twice the size! Net effect probably similar dimensions for the winding.

Simon-in-Suffolk posted:

Mike, yes in a regular European 3 phase system. The US high power distribution system that I believe is now installed in all new buildings in the US  uses L1 and L3 which are 180 degrees out of phase of each other as per your diagram  i.e. L1 and L3 balanced around a centre ground.

And the discussions about how a nominal 240v domestic supply is derived in the US, with all the variants that might apply in different locations and ages of property, all point to it being essential for the OP to find out the definitive position is in his property before being able to consider if it is a feasible suggestion.

Not as I understand it Simon, US domestic voltages are 120V line to neutral  & 240 V line to line (between 2 of the standard 3 phase supply)     This gives 120V for light power items & 240V for high power - AC, heating, cooking.    

My diagram is symmetrical 3 phase & as such are 120 degrees   (240V L2 to L3 on the delta (wye) diagram)  

fatcat posted:

Doesn't ohms law state the higher the voltage, the higher the current, given resistance is constant.

Yes, but but we typically use electricity to power things, i.e. achieve work. Power = Voltage x Amps... therefore for a given amount of work or power , if the voltage is reduced the current has to increase.

in your ohms law example, the power would not be constant, as the heat would increase from the resistor as the voltage and current increases.

Simon.

As I understand it, the amount of power used is dependant on how much the circuit being powered is calling for, for example a 500VA transformer doesn’t push out 500VA. It’s capable of that, but only when the circuit demands it

 So, in the case of somebody being electrocuted, half the voltage equals half the current (ohms law)

 Power = Voltage x Amps (current). If V is halved and A is halved, that means P is quartered.??????

Innocent Bystander posted:

fatcat posted:

Allante93 posted:

A couple of Authorized Dealers, suggest it was ok, by letting me know, they could have it converted from 230 to 115.

Not 100% certain, but converting from 230v to 110v will effectively reduce the number of primary windings by half. Surely this is effectively the same as using a transformer that is half the size. Probably not a good thing.

 Although I could be wrong.

No, half the voltage means twice the current for the wame power, so wire twice the size! Net effect probably similar dimensions for the winding.

In this case we’re talking about converting a 240v transformer for use with 110v. The wire gauge is what it is, it can’t be increased. (Or should that be increased.)

Would this have any implications with regards the power the transformer could deliver. Would it be reduced.

Fatcat, you may well be right having just perused the subject...   I understand that the body's impedance reduces with voltage, so as the voltage and current increases the resistance actually decreases thereby increasing the current through the body yet further apparently...

Just the thought of that research being carried out makes me shudder.