60Hz vs. 50Hz.

Discussion in 'Highly Technical' started by onix, Feb 28, 2005.

  1. onix

    onix Member

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    The US uses 60 Hz, 120V, and most of the world uses 50Hz, 210-240V. Was there some historical marketing ploy which drove these two different standards? Were these standards in place before TV?

    Added March 26, 2005, 11AM (PST)

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  2. bobsmith1492

    bobsmith1492 Diamond Member

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    I think I heard the reason once, but don't really remember. It probably just had to do with different people developing the technology since the continents are so far separated; most of the countries in the Americas use 120/60.
     
  3. PowerEngineer

    PowerEngineer Platinum Member

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    here's a l;ink:

    Most countries in the world have standardised their electricity supply systems to one of two frequencies: 50 hertz or 60 hertz. The list of 60 hertz countries, most of them in the New World, is shorter, but this is not to say that 60 hertz is less common. The 60 hertz countries are: American Samoa, Antigua and Barbuda, Aruba, Bahamas, Belize, Bermuda, Canada, Cayman Islands, Colombia, Costa Rica, Cuba, Dominican Republic, El Salvador, French Polynesia, Guam, Guatemala, Guyana, Haiti, Honduras, South Korea, Liberia, Marshall Islands, Mexico, Micronesia, Montserrat, Nicaragua, Northern Mariana Islands, Palau, Panama, Peru, Philippines, Puerto Rico, Saint Kitts and Nevis, Suriname, Taiwan, Trinidad and Tobago, Turks and Caicos Islands, United States, Venezuela, Virgin Islands (U.S.), Wake Island.[1] (http://www.philip.allen.org/voltages.htm)

    The following countries have a mixture of 50 Hz and 60 Hz supplies: Bahrain, Brazil (mostly 60 Hz), Japan (60 Hz used in western prefectures).[2] (http://www.50hz.com/pwchrt2.htm)

    Most countries have chosen their television standard to match their mains supply frequency.

    It is generally accepted that Nikola Tesla chose 60 hertz as the lowest frequency that would not cause street lighting to flicker visibly. The origin of the 50 hertz frequency used in other parts of the world is open to debate but seems likely to be a rounding off of 60hz to the 1 2 5 10 structure popular with metric standards.

    Other frequencies were somewhat common in industrial use in the first half of the 20th century, and remain in use in isolated cases today. 25 Hz power, much of it generated at Niagara Falls, was used in Ontario and the northern USA. Some 25 Hz generators were in use at Niagara Falls up until the mid-1990's, for large industrial customers who did not want to replace existing equipment. The lower frequency eases the design of low speed electric motors, especially commutator-type motors for electric traction applications such as railways, but causes a noticeable flicker in incandescent lighting.

    Off-shore, textile industry, marine,computer mainframe, aircraft and spacecraft applications sometimes use 400Hz, for technical benefits of reduced weight of apparatus or higher motor speeds.

    16.67 Hz power is still used in some European rail systems, such as in Sweden.

    It should be noted that AC-powered appliances can give off a characteristic hum at the multiples of the frequencies of AC power that they use.

     
  4. Geniere

    Geniere Senior member

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    Power Engineer ? Very nice!

    If the power utilities were to start with a clean sheet, what frequency do you think they would agree on?
     
  5. Peter

    Peter Elite Member

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    German rail also still runs on 16.7 Hz. I can tell ... everytime one of those high-speed "ICE" trains flies by, I get 16 Hz flicker on both my 20" CRTs ... although I live some 200 meters from the track.
     
  6. Calin

    Calin Diamond Member

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    50 Hz is enough for the current incandescent light to not flicker. Also, the lower frequency makes the generators a bit more efficient (they work at a lower rpm, so they work with less mechanical resistance).
    For older incandescent lights that worked at a lower temperature, maybe the flicker at 50 Hz was visible. All I can say is that now there is no problem.
    Why lower/higher frequencies are preferred sometimes? The usual AC electic motors (single pole, one phase, with solenoids on the stator and a cage as the rotor) have the 0-torque rpm equal to the frequency Hz of the AC. At lower frequencies it works as a motor, at higher frequencies it works as a electomagnetic brake. If you want to use low rpm electic engine, you either use a reducing transmission, or lower frequency.
    Higher frequency might be used because it can reduce the weight of the transformers (the solenoids can have lesser revolutions as the higher frequency current needs less impedance from the solenoids.
     
  7. bobsmith1492

    bobsmith1492 Diamond Member

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    I can't stand even 60 Hz flicker on fluorescent lights... I couldn't even imagine 50 Hz. :confused:
     
  8. Leper Messiah

    Leper Messiah Banned

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    ^^ I concur. Same thing with my monitor. has to be at least 72hz, so I can stand it.
     
  9. Calin

    Calin Diamond Member

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    Incandescent lights at 50 Hz have no flicker - I can tell you first hand. The fluorescent ones indeed flickers at 50 Hz, but it is visible only on periphereal vision (not that it is not disturbing this way)
     
  10. onix

    onix Member

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    The reason you cannot see incandesent bulb flicker is because it does not cool down (dims) sufficiently between cycles, and the 60Hz actually delivers power at 120Hz.

    The nice thing about 60Hz is that it can be used to sync clocks. The accuracy at 60Hz is precise because power circuits are matched for this frequency and the power companies do not want power being reflected back.

    Why 50Hz vs. 60Hz pre-TV still seems to be a mystery.
     
  11. JTWill

    JTWill Senior member

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    Westinghouse, for the US, It is as simple as picking a standard. The reason most countries use 240v is expense, it is one less transformer stage, It also alows for a smaller wire guage from lower current required. At 1200watts a 120volt system needs 10 amps at 240 it needs 5amps. 20amps needs the same wire size from 120v or 240v. It is cheaper to use 50Hz in power generation but you lose on the true RMS on the voltage. There is a whole science behind the use of the AC waveform .
     
  12. blahblah99

    blahblah99 Platinum Member

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    Because we're the only ass-backward country in the world that likes to do things differently... left hand driving, 60hz, imperial units,...
     
  13. PowerEngineer

    PowerEngineer Platinum Member

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    The choices of 60 Hz and 50 Hz were both rather arbitrary. (There's no RMS difference)

    Lower electrical frequencies require more iron in their transformers because the magnetic fields that accompany their AC currents change less rapidly and so saturate the iron more readily. On the other hand, the changing magnetic fields induce eddy currents in the iron core that obviously increase with the increased rate of change caused by higher AC freqencies. The same trade-offs apply to electrical motors too. (And that's why airplane power systems where weight is important use much higher frequencies.)

    So (generally) 50 Hz transformers/motors have higher initial costs but lower operating costs and longer lives.

    There is no magic for time synchronization using 60 Hz. Power systems generally maintain their nominal frequencies, but the actual frequency is fluctuating all the time (usually within +/-0.05 Hz). Inadvertent power flows triggered by frequency deviations in one direction usually cause deviations in the opposite direction when the power is returned. The integration of these frequency deviations is expressed as "time error". Indeed, a clock built to keep correct time by running at exactly the nominal frequency (either 50 Hz or 60 Hz) will run fast and slow with the actual frequency and show an accumulated "time error" in seconds. It's not that unusual for the "time error" to reach several seconds before special actions are taken, and that's more because large values signify a persistent frequency deviation than it is a concern over the accuracy of clocks.
     
  14. bobsmith1492

    bobsmith1492 Diamond Member

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    240 volts is also much more dangerous, however, which is a good reason to use it for the majority of houshold appliances. It's a lot tougher to kill yourself on accident with 120 volts than 240, not to mention arcing, insulation and fire issues.
     
  15. Cha0s

    Cha0s Banned

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    its different when it comes to light, I couldnt see it flicker at 50mhz, but i can see my monitor flicker at 75Hz..
     
  16. jagec

    jagec Lifer

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    umm? /checks location just to be sure

    Half the world uses 60Hz, half uses 50, it's not just the US.

    We drive on the RIGHT here, like most of the world.

    I agree with you about the Imperial units, though.

    you a hardcore Darwinist or something?;)
     
  17. Calin

    Calin Diamond Member

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    The nice thing about 50 Hz is that it can be used to sync clocks. I also have a radio with digital clock that takes its timing from the 50Hz of the power socket
     
  18. bobsmith1492

    bobsmith1492 Diamond Member

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    The nice thing about 60 hz is that it can be used to sync clocks. I built one myself using a small microprocessor. ;)
     
  19. sharkeeper

    sharkeeper Lifer

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    Clocks using the fundamental (analogue sinus) have the advantage of no cumulative error.

    The incandescent bulb will not flicker (or produce stroboscopic effects on moving objects) as pronounced as discharge lamps due to the persistence. The attack and decay times are quite buffered. Think of it as a ripple filtered source of light. :) The eye cannot detect it but its there. Connect a solar cell to your computer's microphone IN and shine it at a tungsten bulb running on A/C once.
     
  20. gsaldivar

    gsaldivar Diamond Member

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    :roll:
     
  21. jagec

    jagec Lifer

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    Newsflash: The nice thing about ANY constant frequency is that it can be used to synch clocks.
     
  22. Calin

    Calin Diamond Member

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  23. Bassyhead

    Bassyhead Diamond Member

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    Whether you're electrocuted by 120 or 240 I don't think matters at those voltages. The circumstances of how you're electrocuted is going to be a greater factor (were you grounded, where the current takes a path through your body, etc). Also it's the current that kills, not voltage otherwise static electricity, sometimes in the hundreds of thousands or millions of volts, would kill frequently.
     
  24. Calin

    Calin Diamond Member

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    Sometimes the houses catch fire because of the overheating wires in the walls. In this case, higher voltage = lower current = lower heat in the wall.
    And the voltage that can kill you in a bathroom is around 50 V (or maybe less). So the fatality rate depends alot of other things
     
  25. thunderroller

    thunderroller Senior member

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    that depands upon the power genration sorce
     
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