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Why 220@50hz and 120@60hz?

  1. Nov 22, 2004 #1
    Why 220v@50hz and 120v@60hz?

    Who came up with these and why are they different - especially the frequencies?

    I heard that when Tesla was around, someone wanted the frequency to be @330... why?
  2. jcsd
  3. Nov 23, 2004 #2
    After Tesla won the AC/DC fight with Edison he gained much influence and more or less dictated the 60Hz frequency in the US. I think he had an ulterior motive in that he wanted to transmit power without wires and had calculated the 60Hz frequency was best for that purpose. I have no idea why the European nations choose 50Hz, as it is less efficient to produce and transmit over wire than 60Hz. The best frequency for power transmission is probably moderately higher than 60Hz.

    Consider above opinion not fact.
  4. Nov 23, 2004 #3
    I suspect it was to do with how fast the old generators could spin before they flew apart.

    If you compare the size and mass of a 10 killowatt aircraft generator or induction motor (which run at 400 Hz) with a 10 killowatt 50 or 60 Hz unit, you'll be left wondering why we're not using higher frequencies (the equivalent aircraft units are tiny).

    I suppose the frequency can't be too high for long distance transmission of power (there would be more losses), but I suspect it could easily be a lot higher than 60Hz.
  5. Nov 23, 2004 #4
    from what i understand europe picked 50Hz because it was felt it be easier number to work with due to the metric system as for the voltage, that is what edison picked when he came up with dc
  6. Nov 28, 2004 #5

    That's a horrible reason. :D
  7. Nov 28, 2004 #6


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    I seriously doubt it.
  8. Nov 28, 2004 #7

    Ivan Seeking

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    Here is some information on the evolution of 50 Hz. It seems that a combination of the engine and generators used, the ideal engine speeds, the desired voltage, and the number of poles used in the generators drove the selection of frequency in a complex fashion. I doubt that any simple answer exists.
  9. Nov 28, 2004 #8
    There may be some places in the world that use 20 Hz. The old streetcar used 20 Hz. When they were taken out of service the power plants were sold to some cities in other countries. They were still in use about 20 years ago. I think the reason they used 20 Hz back then is that they used rotary rectifiers. The motor on the streetcar was DC.
  10. Dec 4, 2004 #9
    Up to the '40's the iron laminations of rotors and stators of electric motors and generating equipment were poor quality and hysteresis losses were a major factor. (note how large old electric motors are compared to newer ones). Higher frequencies would have worsened the losses so up 'till then 25 Hz was common in Canada and the US.
    When better steel was used for laminations, north America changed to 60 Hz about 1950, the Europeans decided 50 Hz was the cat's meow.
  11. Dec 13, 2004 #10
    I heard that the European used 50Hz becasue it apparently interefered with you heart less that 60Hz.
  12. Mar 27, 2006 #11
    Reasons for 60Hz

    I heard two different reasons for the US choosing 60Hz. One as mentioned above, the Europeans chose 50Hz because of better calculations with the Metric system. Likewise, the US chose 60Hz to better measure periodic voltage (60 minutes, 60 seconds).

    The other, more 'Urban Legend' reason why the US choose 60Hz was in one of its first applications--The Electric Chair--it was determined that 60Hz was the optimum Frequency to Kill a human. This then became the standard. LIKE I SAID I HEARD THAT RECENTLY FROM AN MIT PHD Professor. Doesn't make that much sense though if you consider that same danger is being carried out to every home.
  13. Mar 28, 2006 #12


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    I once heard that the reason for 60 hertz is that is was the highest frequency you could get without developing standing waves on a trans-continental transmission line.
  14. Mar 28, 2006 #13


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    He's wrong.
    Edison was desperate in his attempts to discredit Westinghouse's AC system and was resorting to all sorts of public relation propaganda to prove how dangerous it was (including the promotion of the electric chair). It was hardly to Westinghouse's (or Tesla, his top engineer that designed the modern 3 phase system) advantage to promote the "deadliness" of his product.
  15. Apr 19, 2006 #14
    Not to dig up a dead thread but I read a biography on tesla 2 years ago and remember reading about the 50hz vs 60hz debate. Tesla intended his generators to be run at 60hz but the french operators (at the first ac generator in europe) didn't want to speed up their machines, or something the like. From that point on every one just followed suit and didn't question, untill now ;-)
  16. Apr 20, 2006 #15
    Which makes me question the 15 kV 16 2/3 Hz railroad power that seems to be adapted as a standard in many European countries. Do they use different generating stations than the regular 50 Hz, or do they do some complicated frequency change somewhere along the line?

    And why 16 2/3 Hz? Something with the old locomotives? I doubt it matters much these days with the thyristor locos.
  17. Apr 21, 2006 #16
  18. Apr 22, 2006 #17


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    When I was in Japan, I learned that east is 50 Hz and west 60Hz.

    Eastern Japan 50 Hz (Tokyo, Kawasaki, Sapporo, Yokohama, and Sendai); Western Japan 60 Hz (Osaka, Kyoto, Kobe, Nagoya, Hiroshima)

    Basically, TEPCO (Tokyo Electric Power Co.) is the main supplier in east, and KEPCO (Kansai Electric Power Co.) is main supplier in west.


    Regarding 220 V @ 50 Hz and 120 V @ 60 Hz, IIRC 220V is line-to-line voltage in a 3 phase system, and 120 V is line-to-neutral. This has to do with 'Y' vs [itex]\Delta[/itex] configuration.

    Several electrified railways used 25 Hz in US.
  19. Apr 22, 2006 #18


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    Wye configuration has 120 volts from each phase to neutral and 208 volts phase to phase.
    Delta configuration has 240 volts phase to phase and the neutral is a center tap on one of the transformers yielding a 120 volt line to neutral on 2 of the legs and the wild leg is something like 160 volts to neutral.
    Standard single phase residential is 240 volts line to line and the center tapped neutral is obviously 120 volts to each line. There is only one transformer secondary winding in residential single phase. It is commonly called 2-phase which is incorrect.
  20. Apr 22, 2006 #19
    I recall a story of early lights hooked up to 25 or so Hz giving people headaches and ill effects because you could actually detect the flicker in the lights, which I guess would be frigging irritating after a while.
  21. Apr 24, 2006 #20


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    Although I don't know much about how the ferquencies wre chosen back in the day, I know that now an important consideration in modern times is an interesting phenomenon known as the "skin effect." This strange occurence makes the current distribution concentrate about 80-85% of the total volume current within the skin depth of the conductor. This depth can be calculated by the simple formula shown in this wikipedia article:


    The reason this becomes a problem is that your effective resistance becomes much larger as you increase the ferquency, since your effective area of your conductor decreases as the skin depth gets smaller. This can become a real problem in high-frequency laboratory applications because ferquencies in the MHz range dirstibute most of the current within the first few dozen nanometers!

    Anyway, the article also has a small table showing the skin depth in a copper conductor at various frequencies, the depth for 60Hz is only 8.5mm. For an extension cord this doesn't lead to any probelms, but what about a power trnasmission line that's 2.5" in diameter? Just food for thought.

    Power transmission lines don't use copper, they use stronger metals such as steel I think. The skin depth for steel at the same frequency can be on the order of 1.5mm, futher exacerbating the problem.
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