Why 220 volts?

Discussion in 'General Electronics Chat' started by Nathan Hale, Jun 16, 2013.

  1. Nathan Hale

    Thread Starter Active Member

    Oct 28, 2011
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    why are certain appliances designed to run on 220 volts? why dont the designers design them to run on 110 volts so that we dont need to have a special 220 volt outlet in our homes?
     
  2. #12

    Expert

    Nov 30, 2010
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    A better question is, why not do it like the European countries and use only in the 220 to 240V range instead of the "special" 120 volt sockets in the U.S.?

    The higher voltage allows more power per amp. Calculate a 5KW clothes dryer at 120 volts. That would require 6 gauge wire. Calculate a 10KW residential furnace at 120 volts. That would require more than 100 amps for the circuit breaker, and I'd have to go look up the size of wire! Calculate why I can't get more than 1 horsepower (develops 2 HP) when I buy an American table saw. I can get a 5 horse motor to run on 240 volts with 10 gauge wire, and I did, but I had to design it to use clothes dryer outlets so I could take it to my jobs.

    Now you have my opinion.
     
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  3. tinkerman

    Member

    Jul 22, 2012
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    One reason I don't like 220. Getting zapped by 220 really, really hurts. I only remember getting bitten once. 120 not so bad. 120 DC? Hurts just as much 220 AC.
     
  4. Georacer

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    Nov 25, 2009
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    Which hopefully makes us more conscious about the dangers of live current. ;)
     
  5. Brownout

    Well-Known Member

    Jan 10, 2012
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    In the US, most appliances are 110/115V. But appliances that require more power use 220V. US houses are wired for two phases. 220V appliances connect across both phases. 110/115V appliances connect across one phase and neutral. I don't know why it was set up this way. It would be interesting to know.
     
  6. Shagas

    Active Member

    May 13, 2013
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    120V dc hurts as much as 220AC?

    Doesn't make sense .
     
  7. Brownout

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    Jan 10, 2012
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    I just had a thought... maybe it goes back to Edison's efforts to convince that AC power is dangerous. Maybe 110V "sounds" safer than 220V.
     
  8. studiot

    AAC Fanatic!

    Nov 9, 2007
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    Is there any other sort of current?

    :D :D :D

    It's a better system than the UK / European one (apart from the funny coloured wires) so stick with it.
     
  9. tubeguy

    Well-Known Member

    Nov 3, 2012
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    Found this on Wiki, section 4:
    http://en.wikipedia.org/wiki/Mains_electricity

    I never knew this, seems there was an Edison effect :)
     
  10. Georacer

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    Nov 25, 2009
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    In Greece (and I imagine the rest of Europe would be similar), the low-voltage power grid has three phases of voltage, at 230V, split 120degrees apart, to power motors in small businesses and newer households.

    The voltage difference between one phase and ground is a sinusoidal with amplitude 230*sqrt(2).

    The voltage difference between two phases is a sinusoidal with amplitude sqrt(3)*230*sqrt(2).


    If is a similar 3-phase distribution system in the US, then the voltage between two phases should be a sinusoidal with amplitude 190*sqrt(2). Where do the 220V appliances tap onto?
     
  11. strantor

    AAC Fanatic!

    Oct 3, 2010
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    Who knows what the original reason was, but this reminds me of something that I read while doing a research paper about developing nations. I don't remember the actual words of the thing I want to quote, but it went something along the lines of (from the perspective of developing nation) "Our strongest asset is that we don't have an existing infrastructure to hold us back." They were talking about the implementation of cell phone service. Many people in Africa never had a land line. The first phone they got was a cell phone with 4G service. Coming into the game late, they have the advantage of starting out with the best technology that we have developed but can't use because we are trying to make our new technology fit our outdated technology. By the time they catch up, they will be miles ahead. Nothing but fiber optic lines and such.

    I suspect this 120V thing is one of those things. There was some reason for it in days past and now it has become a hindrance as we have standardized on it. Upgrading to a better voltage is out of the question, so we are stuck with it. But developing nations aren't.
     
  12. Brownout

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  13. PackratKing

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    Jul 13, 2008
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    Most appliances you will run onto, using 240, are equipped with the special plugs ...
    As with most clothes dryers, air conditioners, when you look inside, the compressor / heating coils are on one phase of the 240, and the drum / circulation motor are on the other phase... so yes, they are hooked up to 240, tho' that is just for wiring convenience...

    My lathe - a Rockwell /Delta 11 x 36 has a 240 volt single-phase 1 HP motor... as does my 2-stage air compressor, though it has a 1 1/2 HP repulsion-start motor - brushes as the "start" circuit... I run either with the 240 and both employ the neutral...
     
  14. studiot

    AAC Fanatic!

    Nov 9, 2007
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    The US split phase (not two phase) system is nothing like the European three phase system.

    In the US the supplier provides phase and return (but not earth) to individual consumer transformer's primaries.
    The transformer provides 120-0-120 to the consumer, by means of a centre tapped secondary.

    The consumer provides his own earth by earthing the centre point. He also takes his 'neutral' from this centre tap.

    Low power equipment receives 0-120 from the consumer neutral and one side of the Tformer or the other.
    Highpower equipment eg air con is connected across both sides.
     
    Last edited: Jun 16, 2013
  15. tubeguy

    Well-Known Member

    Nov 3, 2012
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    rs
    In the US commercial buildings and manufacturers receive the 3-phase 240 or even 480 volts at 120 degrees.

    The residential users receive what's called single phase which is two 120 lines 180 degrees out of phase with a single neutral.

    EDIT: I type too slow ... :)
     
  16. Georacer

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    Nov 25, 2009
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    So the low voltage, consumer US distribution system runs at 220V RMS per phase?
     
    Last edited: Jun 16, 2013
  17. #12

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    Nov 30, 2010
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    Maybe we should ask Ben Franklin. He's the genius that decided electrons are negative, right?:D

    While we're chewing on this, 40 years ago the usual "delivered" voltage here, west Florida, was about 117 VAC RMS per phase, and I sent many a customer to complain to the power company when their air conditioner wouldn't start as the power voltage dropped below 97 volts during a start surge (which is about 5 to 8 times the running current). Now, the "standard" is 240V, split phase, +/-5% and my house receives 250.0 volts.

    Being both smart and cheap, I still use a 1979 clothes dryer, but I can't run it with the coiled nichrome elements designed for 1979. They burn out in about 3 weeks. I had to replace them with Calrod brand heaters because they could survive the higher voltage.

    I expect that newer appliances are designed for the higher voltages we have now, but I sure don't know why the voltages keep changing to higher numbers.

    All of that rambling, so far, was about U.S. residential power service. It seems that all the other sorts of service are available, for a price, if that's what you need. Three phase at 230V or 460V are common enough that even I have met them. It seems like the reason is always about getting enough power to the equipment without dragging in wire that weighs 2 pounds per foot. Think about this: How would you like to wind a 5 horsepower motor with 6 gauge wire so it can run on 120 volts, single phase? You would be tempted to start by designing the machine that can wind wire that size into a field coil (stator).

    All the while, I'm ducking in case somebody shoots the "other" voltages at me. 110, 115, 117, 120, 125, 208, 220, 230, 240, 250 have all been encountered over the last 40 years and I don't have a clue as to why. I just make the machines work...which brings me to another subject I'm going to ask strantor about.
     
  18. tubeguy

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    Nov 3, 2012
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    I must correct myself regarding 3-phase. I recall when I worked on commercial food processing machinery the 3-phase voltage I usually measured would be about 208 - volts, not 240 3-phase.
     
  19. studiot

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  20. Georacer

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    Nov 25, 2009
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    Aha! I see what the deal is.

    It's strange how different electrical systems can be in two parts of the world. Parts which otherwise try to keep up with each other.
     
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