Why the difference between European and American Mains?

good question, Europe is now 230 all over, we used to be 240 in the uk till a few years ago

quote:

Originally posted by Aric:
I was wondering if there's a technical reason, or if it was purely arbitrary?

What does the Asian mains run at?

Aric

I heard the Southern US States had 3 phase stuff to cope with the extra chairs ?

Fritz Von Amplitudinously Moderated Wot

Many years ago when the americans had two competing systems:

ac and dc the argument against dc was that it was so lethal that the US govt used it as its choice of execution.

Sort of resulted in AC as the system of choice for non lethal use.

regards David

http://kropla.com/electric.htm is useful.

More on: - http://kropla.com/electric2.htm

Thanks Adam. That certainly addresses my second question.

Did the EU switch to 230 volts because that was the most prevalent?

Are there any EE's who can comment?

Actually it's in the name of EU harmonisation, but there is/was effectively no actual changeover. What happened was a subtle re-writing of tolerances to acheive a mean of 230V across Europe. For example, the UK used to be 240V +6/- 10%; this is now 230V +10/-6%. If you run the numbers you'll see nothing has really changed - indeed c.240V seems to remains the delivered norm*.

Similar exercises were enacted in formerly-220V countries; but it means that now there is effectively only one standard to design domestic appliances for.

M. (no EE!)

*with much tighter regulation than allowed - I have a couple of bits of equipment permanently on a metering device, and I see about 238V +/- 1V

Practically speaking, higher voltages allow more power with less current and therefore smaller wire diameter can be used (cheaper, lighter, all that). Since Power = Voltage times Current you can see that for the same power doubling the voltage allows for half the current.
On the other hand, you need more insulation for safety.
Along the same lines, 60Hz allows for smaller magnetics than 50Hz. So, the gains of smaller wire diameter are offset to some degree by the larger transformers required in distribution.
Edison was fixated on supplying DC to the masses, it is to this day totally impractical for distribution.
However, when I was working in Chicago in the 1980s there were buildings that still had DC line running to offices. The power company had to keep them on as they had some customers with very old equipment that still used it. Amazing. And very dangerous.
I understand that the combination of 120-240V with 50-60Hz is a poor choice in that the voltage is plenty high enough to break down the insulation of human skin and the frequency is just slow enough to allow you to stick to it. Other combinations of voltage and frequency might be safer to work with but completely impractical especially given the world-wide infrastructure.
As to why Europe and many other parts of the world settled on a 230 (ish) standard and the US and others went for 120 is not clear to me. And Japan with their 100V and the North/South split on 50 and 60Hz. Oh my, what a headache that must be!
A consequence of Naim having the good sense not to willy-nilly throw switching power supplies at everything is that re-wiring of the transformer primaries must be done before plugging into a different voltage.
One last point: I tried to engage a discussion on whether separate spurs (and all that forbidden wiring discussion) would have a larger impact in the US since our wiring must carry twice the current (and 4 times the power loss due to wiring impedance) but no one would bite.
David

Martin & David,

Thank you for your informative replys. So it seems that the initial standard set forth many decades ago for each country was dependent upon wire diameter and insulation.

Pro and cons to both I guess.

Aric

IIRC, construction site equipment in the UK runs at 110-20V, because it's non-lethal.

I know, I know, current kills you, not voltage, but that's what I remember from my construction design leactures.

I always understood that construction site equipment ran at 110v to dissuade users from taking the equipment home for DIY work around the home.

Yup, UK site equipment is generally supplied 110v from those yellow transformers, which are centre-tapped to Earth. Ths has a couple of advantages:

1. It limits shock-to-earth potential to 55V, definitely a good thing given most sites are wet...
2. More subtly, the transformers provide current limiting. You'll find they run hot at normal loading, this is by design (deliberately undersized cores). If you short one, the transformer (3KVA 'cube' type) generally won't supply more than 10-15A, limiting potential for fire etc.

I like Derek's reasoning though

IMO It's a good thing the US only run 120V as their plug/socket system is a health and safety nightmare. Far too easy to inadvertently touch a live pin whilst withdrawing the plug from the socket. The Aussie one is just as bad and they run 220-240V which frightens the hell out of me!

Being an ex BR Power Supplies worker, playing with voltages from 25KV - 33KV, I'd always have liked Mr Parry along with me thinking in retrospect, as although the safety systems in place were far far superior to anything I've ever seen, including the military, I feel Mick's presence would have calmed us in moments of induction² innit.

Fritz Von Trusting your team mates

Many years ago on Taiwan, a friend worked for for the China Electric Brain Company who studied their electric power. In the 2 hour study, voltage varied from something like 30 VAC to 230 VAC, with a nominal 110 or so. Their IBM 7094 never complained....

I suspectthe power has gotten better in the last 30+ years though.

Phil