Question:
Why do we have different supply voltages in different countries? Even frequencies?
innocent
2011-11-28 18:24:48 UTC
For instance in US the supply voltage for domestic use is 110 v while in UK it is 220. In Japan again it is different and in India it is 220. Has it any thing to do with efficiency?
Three answers:
Syam
2011-11-28 20:28:00 UTC
The system of three-phase alternating current electrical generation and distribution was invented by a nineteenth century creative genius named Nicola Tesla. He made many careful calculations and measurements and found out that 60 Hz (Hertz, cycles per second) was the best frequency for alternating current (AC) power generating. He preferred 240 volts, which put him at odds with Thomas Edison, whose direct current (DC) systems were 110 volts. Perhaps Edison had a useful point in the safety factor of the lower voltage, but DC couldn't provide the power to a distance that AC could.



When the German company AEG built the first European generating facility, its engineers decided to fix the frequency at 50 Hz, because the number 60 didn't fit the metric standard unit sequence (1,2,5). At that time, AEG had a virtual monopoly and their standard spread to the rest of the continent. In Britain, differing frequencies proliferated, and only after World War II was the 50-cycle standard established.



However that might have been a mistake! Not only is 50 Hz 20% less effective in generation, it is 10 - 15% less efficient in transmission and requires up to 30% larger windings and magnetic core materials in transformer construction. Electric motors are much less efficient at the lower frequency, and must also be made more robust to handle the electrical losses and the extra heat generated. Today, only a handful of countries (Antigua, Guyana, Peru, the Philippines, South Korea and the Leeward Islands) follow Tesla's advice and use the 60 Hz frequency together with a voltage of 220 - 240 V.



Originally Europe was 120 V too, just like Japan and the US today. It has been deemed necessary to increase voltage to get more power with less losses and voltage drop from the same copper wire diameter. At the time the US also wanted to change but because of the cost involved to replace all electric appliances, they decided not to. At the time (1950s-1960s) the average US household already had a fridge, a washing-machine, etc., but not in Europe.



The end result is that now it may seem, to some people, that the US has not evolved from the 1950s and 1960s, and still copes with problems as light bulbs that burn out rather quickly when they are close to the transformer (too high a voltage), or just the other way round: not enough voltage at the end of the line. (115 to 127 volt spread!).
?
2016-11-05 11:49:56 UTC
Voltage In Different Countries
anonymous
2016-02-27 04:03:45 UTC
I agree with the previous answers but will add an important point about safety. Many people claim that a 120 Volt system is safer than a 240 Volt system. The fact is that there is not a scrap of evidence to support the idea that there are fewer fatal electric shocks in 120 Volt countries than there are in 240 Volt countries.


This content was originally posted on Y! Answers, a Q&A website that shut down in 2021.
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