Europe's electricity runs at 240 volts while the U.S. is 120. Why the difference?

Question

Is there an advantage to having 240 versus 120 volts AC house current?

Answer 1

Technically Europes various voltage standards, which varied from 220 to 240V have been standardised to 230V +10% -6%.

Europe's household supply is based on a three phase 415 V system, using a star would generator with the common point earthed (at the power station and distribution transformer) as neutral. This gives 240V between each phase and neutral.

In the US, the final transformer output is 240V centre tap at earth, with one half going to the house as the supply, along with the earth forming 120V supply.

At 120V, the cable losses are higher as a greater current is required to deliver the same power load, although the lower voltage is often considered to be safer.

Interestingly, the European Low Voltage directive, which is a safety standard for electrical equipment applies to products with a AC supply of 100V or more and DC supplies of 50V or more. I suspect the latter was to permit phone systems to be exempt as the supply is 48V DC, except when ringing as this becomes 100V peak to peak alternating. Phone supplies can be very dangerous, particulay at the exchange, where there are high currents available and very little line drop involved.

It is the current that kills not the voltage. Most people can sense 0.3mA but the safety standards call for protection to limit the current to humans at less than 0.7mA. It doesn't take much current across the body - arm to arm or cross from arm one side to leg the other to stop the heart, that's why you often see electricians working with one hand in their pocket.

Answer 2

Europe was not the first to power their cities, It was the US. And a number of experiements were done on AC verses DC, Edison prefered DC and he stood his ground on the Dangers of AC, " The famous experiement that killed a dog" with 200 Volts AC is well documented. So to get AC approved for house usage, a 110 volt system which would supposively NOT KILL, but just shock was taken as the Philadelphia standard.

The Europeans, however, developed electrical power a couple years later when more data and information on the 110 volt American system became available and the fear of a higher voltage subsided, thus the adoption in Europe of 240 volts became the Standard. The savings in copper for a large continent such as Europe was enormous and America has used countless tons of copper over the last 100 years which it would never have had to use, mainly because of the power Edison had in those days. And as You know, the higer voltage of 240 requires less copper to transmit the wattage, thus the need for copper is greatly reduced.

Edison was a great inventor, but not a technical mathmatical anylist of Electrical Engineering problems, so his intentions were indeed well intended, but very wrong. The AC/DC, A C kills , fiasco was one of his great embarrasing blunders of his life of which he was not able to overcome. It reduced his stature as a scientist and engineer.

Answer 3

Not really, 240 means you can draw larger currents from a smaller cable, although nothing to do with why they are different the windings on a transformer primary side (mains in) can be thinner with a 240 system.

120 is considered safer, Health & Safety requires that working on site is done using a centre taped 110 volt transformer but I don't know any UK sparkys who aren't used to getting tickled from a bit of 240 volts.

Incidentally the UK no longer operates at 240 volts about 10 years ago we dropped to 220 in line with Europe.

Answer 4

The companies that popularized electric distribution in Europe made a different inital choice than the ones in the US. Once people had anough appliances for a specific voltage then the opportunity for a country to change voltage is really gone.

The higher voltage uses a skinnier cheaper wire for distribution (less current needed to get same wattage). However the higher voltage is more lethal if you touch it.

Answer 5

Yes. It means that we Europeans have more cojones than you wimpy American types, with your pathetic 120 volts. Hah!

Answer 6

Europe appears to be a lot smarter than the US, having a 240v power supply is too complicated for the Americans, they may get confused!

Answer 7

With higher voltage, amperage is lower. Amperage must overcome resistance. So high voltage means lower resistance.

Answer 8

Good question!
Can't wait to read the answers.
thanks

Answer 9

according to the NECcode and for more protection for personal