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Re: 120v vs 240v

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  • Craig
    Jong There is another consideration, I will limit myself to the US and the NEC (National Electrical Code). Circuit size is also limited to the wiring. In a
    Message 1 of 35 , Jul 31 8:43 PM
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      Jong

      There is another consideration, I will limit myself to the US and the NEC (National Electrical Code).

      Circuit size is also limited to the wiring. In a circuit protected with a 15 amp fuse/circuit breaker you are limited to wire that is not smaller than 14 awg, while a 20 amp circuit requires 12 awg wire. It is permitted to run 12 awg wire on a 20 amp breaker/fuse to cut down on the voltage drop, however if you attach a 14 awg wire at some point, then you are required to change the fuse/cb down to 15 amp.

      The amapacity charts are based on the conductor, number of conductors and insulation.

      For a quick easy chart check out http://www.okonite.com/engineering/nec-ampacity-tables.html

      To be honest, when doing wiring if you have ANY doubt get a qualified electrician.

      Craig

      --- In Electronics_101@yahoogroups.com, "craig92" <kec-comm@...> wrote:
      >
      > Jong
      >
      > Another issue is to why most of the world uses 50 Hz while the US and other countries use 60 Hz, and to complicate matters at one time the US used 25 Hz, how were these frequencies decided upon.
      >
      > It would not be feasible to change at this point since so much equipment is based on the power line frequency, TV in particular.
      >
      > I am aware that aircraft uses 400 Hz since the higher frequency translates into smaller components and less weight.
      >
      > Craig
      > KEC Communications
      > N9NBO
      >
      > --- In Electronics_101@yahoogroups.com, "jongkung01" <jongkung01@> wrote:
      > >
      > > Hi guys,
      > >
      > >
      > > So here's the follow up on my "115v or 120v"
      > >
      > > What is "better" - 120v or 240v? Now I know each has some benefits, but what are they? I know that 240v require 1/2 the current to do the same work (maintain the same watt rating). I heard that 240v is more dangerous to human life. True?
      > >
      > > So why did USA go with "120v" instead of the world wide 240v standard? What would YOU choose if you were the one making a choice for your country (consider everything - including political, international compatibility, etc.)
      > >
      > >
      > > Jong
      > >
      > > P.S. By international compatibility - I mean this: if you were a tiny country and you decide on 360v standard, what are the chances you will get many appliance companies to make devices for your crazy standard. Or if you want your country to ever produce stuff for big market, wouldn't it benefit if you were on the same standard as them?
      > >
      >
    • john heath
      USB on computers come with a 5 volt supply built into the USB standard . This is starting to eliminate wall warts for low power devises. It is a little lean
      Message 35 of 35 , Aug 2, 2012
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        USB on computers come with a 5 volt supply built into the USB standard . This is starting to eliminate wall warts for low power devises. It is a little lean for monitors and printers but give it time and they will be running off the computer power supply as well . This should keep the wall worts at bay for the next few years. 
         
        John H

        --- On Tue, 7/31/12, jeremy youngs <jcyoungs76@...> wrote:


        From: jeremy youngs <jcyoungs76@...>
        Subject: Re: [Electronics_101] 120v vs 240v
        To: Electronics_101@yahoogroups.com
        Received: Tuesday, July 31, 2012, 5:40 PM


        ive often thought of a dedicated dc system in the house to get riof all the
        parasitic wall warts etc and run consumer electronics from, but then you
        end up converting everything thing you own. Isnt it great thiks engineering
        always being a compromise!!!!!

        On Tue, Jul 31, 2012 at 8:35 PM, Shawn Upton <kb1ckt@...> wrote:

        > **
        >
        >
        > On wikipedia it talked about using down to even 8Hz on the big motors.
        > Eddy current losses at the begining of the 20th century were a big problem
        > apparently.  If we used 400Hz today, well I'm guessing the transmission
        > line effects still wouldn't occur: but copper losses would certainly go up,
        > due to (again) eddy effects (this time in the problem of skin depth).
        >
        > Given how much DC ultimately runs the world I'm kinda surprised no
        > high-rise has bothered to go to DC to run computers.  Run a big AC to DC
        > convertor, put a big battery across it as a filter, and then run DC to the
        > computers.  Done right the need for emergency lighting would go down (think
        > of the glow put off by the LCD's).  Efficency tends to scale with size
        > also, so perhaps the calculations per Watt would go up too.  Yes, you'd
        > still need to buck down the DC but you could save on the losses of the
        > bridge rectifier.  [Obviously motors would still run on AC.]  I know it'd
        > be another wire in the wall; but that was somehow dealt with when Cat 5 had
        > to be run everywhere.
        >
        > But maybe the losses aren't that bad, per bridge rectifier.
        >
        >
        > Shawn Upton, KB1CKT
        > NAQCC 4723
        >
        > ________________________________
        > From: jeremy youngs <jcyoungs76@...>
        > To: Electronics_101@yahoogroups.com
        > Sent: Tuesday, July 31, 2012 7:17 PM
        >
        > Subject: Re: [Electronics_101] 120v vs 240v
        >
        >
        >
        > ok guys just to throw a little more ot on this why did we coose 60 hz? this
        > seems to me even less intelligent than the 110/220 thing. If we used 400hz
        > our power supplies inductors and transformers would be at least 1/3 there
        > current size and dramatically reduce the cost of manufacture
        >
        > [Non-text portions of this message have been removed]
        >

        >



        --
        jeremy youngs


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