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Old March 10th, 2006, 03:23 PM   #1
Pandiani
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OT: american and european el. power system

Hello guys,
I know this is not "on topic" question but I need to ask a few questions that always
interested me, but I didn't have chance to get appropriate answer.
First of all in Europe we use single phase voltage 230 V and 50 Hz frequency,
and I know that in USA, Japan (maybe in some other countries too) voltage is 120 V
and frequency is 60 Hz. Why is that so?
Second, in school we learned that it is always better to transfer el. power with
higher voltage and lower current because of Joule's losses (I^2*R). However, does
that mean that in USA there are more losses in powerlines because of higher current
comparing to Europe's ( I assume transfered power is approximately the same)?
What is, according to your opinion, main reason that USA chose 60 Hz and 120 V?
I really never had chance to aske these question to any american el. engineer so I ask
here, I hope you won't mind.

Thanks in advance
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Old March 10th, 2006, 03:51 PM   #2
mgvol
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I'm not sure about the history behind 60Hz, but as for power transmission, we use 13.8KV, 500KV, etc.
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Old March 10th, 2006, 04:06 PM   #3
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Originally DC power was used for lighting, this was developed by Thomas Edison. A War of Currents developed between Edison and Westinghouse because George Westinghouse developed high voltage transmissions through the use of transformers. He also hired Nikolai Tesla as a consultant and to develop a polyphase motor and 3 phase distribuion system, it was Tesla that decided to use 60HZ because it was high enough to minimize light flicker but low enough to reduce reactive losses. Since this was the first it became the standard in the US.

I assume that Europe development decided on another standard to avoid patent type issues. Politics etc added to the field since many areas were attempting to develop electrical power systems at the same time. I do not know why Europe chose 50Hz but I assume whoever first developed it used that so the others had to follow, even then their were differences in the voltages...ie 200, 220, 230, or 240. I am refering to base voltages supplied as standard, these could be different depending on country.
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Last edited by rsdoran; March 10th, 2006 at 04:13 PM.
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Old March 10th, 2006, 04:09 PM   #4
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As far as i know some of the HVoltages present in the Uk are

11,33,110,220,275,380 & 400KV
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Old March 10th, 2006, 06:03 PM   #5
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Talking

I am not for sure but I remember hearing that the 50Htz was associated w/ the metric system...just my 2 cents...

David
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Old March 10th, 2006, 06:29 PM   #6
rsdoran
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That makes sense because 50Hz would equal .02 secs or 20ms instead of our 16.6666666667, that would make it easier to use with a metric system.
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Old March 10th, 2006, 06:38 PM   #7
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Somehow I don't think metric was really all that common when the power systems were developed...

As for 60hz I was told back in school that Tesla actually did a short study pulling people off the street and asking them which light bulbs flickered and which didn't. The big attraction to DC power distribution in the early days was that your lights didn't flicker.

I'm going from memory here, but I think his test was this:
One bulb on DC,and several on AC; from memory I think he tried AC frequencies of 30hz, 40hz, 50hz, 60hz, 70hz, 80hz, 90hz, and 100hz.
He asked each person to tell him which bulbs were AC powered and which ones were DC powered based on the flicker. 100% of the people said the bulbs on 60hz and above were DC powered because they saw no flicker so he went with 60hz. As I recall the number of people who saw flicker in the 50hz bulb was low (like 1%), but regardless he decided on 60hz.

Again this is going off memory, I may well be wrong as that particular class day was a long time ago.
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Old March 10th, 2006, 06:41 PM   #8
Mickey
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See this
http://www.ieee.org/organizations/hi...ml#60%20cycles
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Old March 10th, 2006, 07:32 PM   #9
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Now US uses 60Hz Europe uses 50Hz...Why do air craft use 400hz????

anyone??
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Old March 10th, 2006, 07:34 PM   #10
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400hz goes back to radar on Navy ships... As to aircraft I have no idea, but it might have to do with navigation/communication equipment...
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Old March 10th, 2006, 07:44 PM   #11
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another thing...UK uses 220v HOWEVER!! on a constuction site all power tools are 110v This i was told, way back when, was for safety resons
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Old March 10th, 2006, 07:57 PM   #12
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400 hz also lightens the transformers and motors. Efficiency goes up with frequency, as does skin effect.

I thought that the 60hz had to do with time - but the light fliker seems to be a reasonable explanation. (I saw on the history channel that maritime slang refers to the interior crew areas of a ship as the "flicker" - a reference to flickering lights on old ship 25 hz systems.)

Many early US power plants distributed AC at 25 hz. The Niagra generating station still generates 25 hz for some large customers.

Also many people may not be aware that in the USA most homes have 120 Volt and 220 Volt outlets. Most homes are fed with a three wire system that consists of 2 legs plus a neutral. Stoves and ovens, clothes dryers, and other large appliances use 220v.

480V is probably the most common industrial voltage.

Last edited by TConnolly; March 10th, 2006 at 08:31 PM.
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Old March 11th, 2006, 02:29 AM   #13
Pandiani
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Quote:
Originally Posted by mgvol
I'm not sure about the history behind 60Hz, but as for power transmission, we use 13.8KV, 500KV, etc.
Yes, and in Europe as far as I know tnransmission voltages are 11, 35, 110, 220, 400,.. kV, but I was more interested in transmission to houses ( 120 VAC, and in Europe 230 V AC).

Thank you all for your replies...
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Old March 11th, 2006, 04:56 AM   #14
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Quote:
Originally Posted by Alaric

Also many people may not be aware that in the USA most homes have 120 Volt and 220 Volt outlets. Most homes are fed with a three wire system that consists of 2 legs plus a neutral. Stoves and ovens, clothes dryers, and other large appliances use 220v.
Wait, does that mean that in USA home is not supplied with 3-phase power ( 3 phase + neutral wire), but with two phase?
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Old March 11th, 2006, 05:29 AM   #15
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2 phase is not the correct terminology, it is single phase with a neutral..ie 2 hots and a neutral. This is accomplished by various methods.
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