lyxo

So, everyone that knows that all of the United States' and North America's appliances are 110V knows that mostly everywhere else in the world has electrical appliances that are 220V.

I've been searching google for quite some time and can't get the answer to this, so I'm hoping there's a physics major or electronics major out there somewhere that can help me out here.

I'm just wondering what the difference would be between the two, and why it isn't a global standard to have one.

Thanks.

lyxo

anyone? please?

saltfish

USA uses 60HZ 110-120VAC RMS...

This means that the root mean square of the sinusoidal wave that carries the current in our wiring is 110-120V.

60HZ means that the polarity of the electricity goes from positive to negative and back to positive 60 times a second.

Across the pond, they use 220VAC RMS and at a frequancy of 50HZ; twice the voltage but, a slower waveform.

Why? I have not a clue. But I like 60Hz.

-SF

shakran

basically the reason the US doesn't have all its appliances at 220 is because they think the average U.S. citizen is too stupid to have 220 everywhere without killing himself. And they're probably right. That's why we only have 220 in big appliances where the plugs are generally not accessible

goddfather40

Are you saying 120VAC won't kill you?? I think it is just as dangerous. Current is the real concern with electric shock.

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John Henry

Here in the UK, we have 230V. While I would not recommend plugging yourself in, I have received a number of zaps from the mains and survived with no more (noticeable) damage than a slightly tingly arm.

It's a while since I studied this and I don't remember the equations, so don't take this as gospel, but...

What kills you is not 'amps' or 'volts' or 'hertz', but something called 'skin depth'. This is a measure of how far one 'wave' from the mains can penetrate into you, because if the current is only going into you, not through, it will stop after one wave and 'flail' inside you like an untethered bit of string. Basically if it gets to your heart, you're fucked, but how far it gets depends on current, voltage, frequency and your resistance.

I know that some of the places we fix for have modified power supplies that go from -115V to +115V, whereas the mains goes from 0 to 230V. It may be that this is what you have in the States. Do you have two fuses in your plugs or one?

As I see it, the 0 to 230V system has the disadvantage that if you do get zapped by the mains, you have all its energy being delivered to you, not just half of it. With the -110V to 110V I suppose the disadvantage is that if the fuse on one side blows, the other side has one less place to short out to if it fucks up, making it more likely to zap you. Having said that, if that happened, I suppose the extra current the appliance would try to draw would just blow the other fuse as well. Beats me. As I say, this is all off the top of my head, so don't go testing it in any dangerous ways, but I hope it helps.

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shakran

Not at all. But it's much less likely to kill you than 220. In this country, the public is assumed to be stupid (this is why car sunshades have a label telling you not to drive with the sunshade in the window).

And the reason you didn't get shocked that badly on your 230v connection is probably because you only touched one leg of the circuit, which means you weren't getting 230, you were getting 115.

as for fuses, they've been largely replaced by breakers. the 220 breakers have what's called a common trip, which means when one leg trips, the other leg goes with it.


as for skin depth, the reason you get shocked is because you complete a circuit, which means the electricity enters your body at one place and leaves it at another. It's not gonna go 3 inches in and then stop. If it does, you won't feel a thing because your body doesn't have enough conductvity to complete the circuit. Actually it IS the amperage that kills you. the higher the amps, the more power gets shot into you. You take the amperage and factor it with the person's personal conductivity to figure out how bad the shock will be. Personal conductivity varies based on conditions. A guy without much body fat who's not overheated will get less of a shock than a fat guy drenched in sweat. The fat and the sweat both act as conductors.

You can decrease the risk of getting shocked by 1) turning off the breaker to that circuit. 2) whether you turn the breaker off or not, work as though the wire is still live. 3) follow the one-hand rule. Only one hand touches the wire at any time. Two hands on the wire means the electricity will travel straight through your heart. 4) whatever hand you're using on the wire, lift the opposite heel. This will make a lower resistance path through the side of your body rather than potentially through the torso. If the shock travels down your side, it'll hurt a lot but it's much less likely to kill you than if it goes through your trunk. 5) Fiberglass ladders ONLY for electrical work. If you don't have one, go buy one. Metal ladders are death waiting to happen. 6) Wear shoes. 7) Don't sweat, and if you're drenched with sweat, go cool off. The water and the salt in the sweat are both conductors of electricity.

lyxo

so pretty much the only reason why there's the difference is shock safety?

what a let down, ive been shocked several times when i was overseas, but it wasn't that big a deal, just a little buzz, but I get really pissed when my appliance motors get busted because of the voltage difference.

ah well.... US method of thinking seems a little off

it's just sad though, my uncle was talking about how only the most "advanced" nations use 110V because 220V is a cheaper method of generation, so the less developed countries can afford it over the 110V. The more "advanced" countries adopt the 110V system because it's safer.
I guess it's the other way around...

shakran

well 220 is cheaper. Look at it this way. You have a 1500 watt hair dryer. At 120v, that draws 12.5 amps. At 220v that draws 6.8 amps.

goddfather40

I don't think skin depth really comes into play in this case. Skin depth is important in high frequency RF applications and represents the depth at which the current density of the signal reaches 1/e of its value.

Skin Depth = 1/(pi*freq*magnetic permeability*conductivity)^1/2

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MSD

The reason he didnt' get shocked bgadly is most likely that nothing on him was grounded.

DO NOT TRY THE FOLLOWING!!!!
Some older electricians I've seen don't use a voltmeter to test a circuit, they'll just lick their thumbtip and fingertip, and touch both contacts, letting the current travel through one and out the other. With a lack of a ground, and no path through the heart or brain, no permanent damage results.

Mephisto2

220/230/240 (many countries share similiar standards) will MOST CERTAINLY kill you if you touch the mains, and are earthed. There are plenty of fatal industrial accidents each year in Europe associated with touching mains electricity.

I presume the same applices for the US 110v standard.

Mr Mephisto

shakran

LOL. Yeah, I worked with an electrician in college once that did that. Dude was NUTS.


And Mephisto, yes you're correct, especially since the mains in the US are* 220. They only get split to twin legs of 110 in the main breaker box.

Vogad

duh....Power (wattage) is the key.... The ONLY way 220 is cheaper is when the power loss due to heating of the wires is considered...
120volts x 10 amperes = 1200 watts
240volts x 5 amperes = 1200 watts

Our 220 (240) is the function of both phases (A&B) feeding current rather than 1 phase feeding from ground (Neutral).


Do we want to get into "Delta" and "WYE" transfomers and the difference between 208 and 220(240)???

gloveshot3

sometimes i think karma has a bit to do with it. i personally have taken 440 volts. i was knocked on my ass, had mild burns on my fingers, and was totally numb for a few seconds. i saw a guy blow the soles off his shoes with 1400 volts, he never got a mark.
i've read about people who have died while trying to replace a lightbulb. who knows.

saltfish

There is a great difference between Voltage (Electrovoltaic Force) and Current (Electron Flow Quantity). Static electricity can reach hundres of thousands of volts, though the current is next to nothing. I have heard stories where people can be easily killed with a very low voltage, it was that they were in a situation where they were very conductive and could pass a great deal of current.
Even 1/10th of an Ampere can be fatal!

Here is some reading if you find this topic interesting:

http://www.physics.ohio-state.edu/~p...l_current.html

-SF

TheBrit

I have had 230 here through me, just a buzz in my arm. By the time I had stopped swearing and had my hand under a tap (wire removed) the pain was gone.

If it is just amps that kills you, then surely the higher the voltage, the safer it is, presuming the same wattage appliance?

shakran

Vogad: I'm sorry, but you're wrong. 220 is more efficient than 110.

TheBrit: I believe you are saying that higher voltage is safer becasue generally the appliances using 220 draw fewer amps than the same appliances would using 110? The problem with that idea is that you are assuming that if you get shocked with 2 amp appliance you will only get 2 amps through you. That is rarely the case - usually you get much more, generally up to (and beyond if there's a problem with the breaker) the amperage rating of the circuit itself. That 2amp draw the appliance lists means it draws 2 amps when it's working properly, and it also does not mean that the appliance reduces the circuit to only being capable of producing 2 amps. In other words, the appliance is supposed to draw 2 amps, and is "set up" so that it will only draw 2 amps. You are not "set up" to only draw 2 amps, so if the current goes through you instead of the appliance, all bets are off - you'll draw however much current your body has the potential to draw.

Now, the really fun scenario comes when the breaker gets fused. I've seen this happen, and when it's fused it can't shut off. That means you could potentially draw 200 amps (or however high the main breaker is rated). You wouldn't be able to do this for very long because the wire would heat up, catch fire, and eventually snap somewhere. However, it can take less than 1 second for the current to kill you, so that wouldn't help you very much.

Sapper

This is an interesting topic.

The trouble with the "cheaper" argument is that as noted before: watts = volts * current

Imagine that the hairdryer in a previous example draws a maximum of 550 Watts .. that would be 5 amps on 110v and 2.5 amps on 220v. Still the same amount of energy .. just different variables This is why the power company bills in Watts and not Amperes

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shakran

They bill in kilowatt-hours, which is a very different thing from straight watts.

Listen, if 220 is no more efficient than 110, then why do heating systems, dryers, ovens, etc. run on 220? Why do air compressors have the option to run 110 OR 220? 220 is more costly to install so it would seem there's absolutely no economic advantage to running it at all. The answer is that 220 is more efficient, gets more work done with less power, and therefore is cheaper in the long run.

Sapper

OMG. Somebody needs to review what power is ..

Voltage is like water pressure.
Amperage is like water flow-rate.

Work = Force x Distance (simplified version)
Work = Voltage x Amperage

Power = Work / Time

Look back at what Work is (in terms of the equation). Work in electricity is expressed in Watts. Notice that the number of Watts is equal to the voltage times the amperage? What does this mean?

Power is dependent on the amount of work over a time period. Let's choose a time frame of 1 minute. Let's also choose a set amount of work, say .. 1000 Watts. Power in this case = 1000 Watt / min

Still follow?

Now let's look at the 1000 Watts of work vs amperage:

amperage (I) at 110v = work (W) 1000 Watts / voltage (E) 110 Volts
amperage (I) at 110v = 9.09 Amperes

amperage (I) at 220v = work (W) 1000 Watts / voltage (E) 220 Volts
amperage (I) at 220v = 4.54 Amperes

What does this mean? Well, it means that if your circut were on a 5 amp breaker .. only the 220v circut would not trip the breaker.

Does this mean that the 220v circut does more work? NO.

Still follow?

So what if the amperage is different? I'm still not convinced that 220v is not more efficient ..

Ohm's law: E = I * R (E is voltage, I is current, R is resistance)

So, let us assume two circuts with the same amperage (I) of 10 amps but the voltages mentioned above .. but this time we will evaluate the resistence in the circut:

R at 110v = E / I
R at 110v = 110 v / 10 amps
R at 110v = 11 ohms

R at 220v = E / I
R at 220v = 220 v / 10 amps
R at 220v = 22 ohms

Suprised that the curcut resistence is greater in 220v than 110v? What does this mean? .. well, it means that more electricity will generally be lost to the system in 220v circuts!

If you are still confused .. let me know what you don't understand and I will try to re-word everything ..

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shakran

http://science.howstuffworks.com/question501.htm

I love that site.

Higher voltage = greater efficiency

220 is more efficient than 110.

Sapper

You obviously can't see the mathematical relationship ... so I can not explain it to you further.

There is a prime difference between AC and DC powerources - the how(we think)itworks site quotes material based on a DC power-system.

Thank Nicola Tesla for the far more efficient AC energy distribution system. Edison wanted a horribly inefficient DC power-grid.

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high_way

i agree with shakran that 220-240 V rms is more efficient.

i read an article a while talking about it. from what i rememember and what i have learnt at work, the fact that 220-240v draws less current it produces less heat thus less power is lost by heat.

i cant remember what was actually said but i will have a look at work and see if i can find the article.

Sapper

Jesus christ.

Of course the 220v will draw less current - but the resistence (due to voltage increase) increases proportionately.

There are so many advanced factors in this problem .. and people can't seem to understand the basics .. its a lost cause.

[edit: less harsh reply]

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shakran

http://home.austin.rr.com/bevhoward/kiln/VoltAmp.htm

http://www.greenvillewoodworkers.com...sletter_03.htm

http://www.faqs.org/faqs/electrical-...ection-11.html

Now will you PLEASE give it up? You obviously know theory very well but you don't know practical application. I guarantee you that a 220 appliance will run more efficiently than a 110.

goddfather40

Ok, Ok, I think I can mediate here a bit. shakran and Sapper both have valid points. It all depends on how we want to define efficiency. I think Sapper interpreted efficiency as 'less costly' in an electric bill kind of sense, in which case since 120VAC and 220VAC will supply equal amounts of power to a circuit with, as one of the links shakran provides says, less than 50 feet of wiring. When the wiring (like house wiring) has more than 50 feet of wire, the line loss at 120 VAC is twice what it is at 220 VAC (purely resistive aka thermal energy loss).... shakran interprets efficiency as power supplied to power consumed. For example, if you have a motor, of which most have coils with hundreds of windings which is made of many many feet of wire, the coil losses are considerably more at 120VAC than 220VAC...one of the links mentions four times as much due to not only resistive losses, but inductive losses as well.

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AlphaFox830

My $0.02

Power = V * I

Ohm's Law: V = R * I


Power (Resistive Dissipation) = I*R^2

Higher voltages are more effecient because they reduce the energy loss due to transmission. (the I*R^2) loss due to heating. The common sense reason that we use lower voltages is that its easier to design.

FYI: 100 Milli-amp's across your chest is enough to cause the heart to fibrilate. (which basically means it rips itself apart... very bad.)

100 Milli amp = 0.1 Amp!

A COMMON LIGHT BULB USES 1 AMP!


Thats all ive got.






As for the original question of an international standard. The united states can not even make a relialbe transmission network across the country. The crisis of de-regulation, and independent power generation cause alot of problems. Added to this is the fact that the transmission grid is being antequated as we speak. This is a billion dollar industry and the industry is under fear that it could be nationalised. (Which i think might be a good thing... but thats just me.)

To give you an idea of how screwed up things are. To transfer power from the west of the mississipi eastward the AC power, say at 765kV must first be converted to DC power. This is because the generators that create the power are not sycronous. The AC waves would cancel at certian points along the grid.

and finally... here is a link for the power industry. Its a preliminary report of what happened last august in ohio, and the midwest.

https://reports.energy.gov/BlackoutReport-1.pdf

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ireallydontknow

i stuck both ends of a paperclip into my 110VAC when i was 5.. what a resistor

Cynthetiq

somewhere there's that picture of a guy standing on an electrical pole and there's sparks and bolts flying about him.. he survived.. he was drugged up or something ...

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spived2

It seems to me that one thing hasn't been brought up in this thread (kick me if it has). What kind of appliances are we talking about? A washing machine and dryer need a lot of power to run, therefore 220 power would be the way to go. You get double the amount of electrons to feed their hungry motors. But for regular wall sockets, why do you need to have 220 power racing through your lightbulbs or computers when you could have 110 pumping out enough amperage to power them easily? Seems that would be a little more efficient.

Please enlighten me though...

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AlphaFox830

And so i shall.

We use 110V AC for wall outlets because the wire in the walls is only rated for say 40amps. (normal household applications, i'll get to HV in a sec.) We also use circut breakers to open the circut if there is a drain of say more then 30A. Its easier, and cheaper to use less copper to wire a home at 110v then it is 220V.

Fox.

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svt

Sapper, you crack me up dude. LMAO

I hear where ya comin from =)

Pacifier

yep, with very high frequencys the electric current only travels at the surfance of the conductor. This is called the "skin effect"
You can even play "magician" by using your body as a conductor for very high voltages:
http://www.ucsc.edu/currents/00-01/a...-10-30.155.jpg
he only survives because of the high frequency.

As for the efficiency, since you have higher voltage you need lower current therfore you can use thinner conductors. Also the loss when tranfering power over a longer distance is lower when transferes whith higher voltage. Here in Germany transmission lines (http://www.zoll-d.de/z1_bilder/a1_vst/strommast.jpeg) uses up to 360 000 Volt

The reason why the USA uses 110V and EU uses 230V are a bit unclear. From what I know at the beginning the first arc lamp used 55V. But that wasn't enough for long so it was doubled. in the USA they thought 110V was enough, in the europe the even quadrupled it. Perhaps it was because in Europe there was a shortage of copper during WW1 and they prefered to keep the conductions as thin as possible, in the USA they decided to live with the higher losses and just build more transformers.

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jujueye

I know of an audio buddy who uses the 220 from his clothes dryer hookup. He splits the two legs of the 220 circuit to two 110s. Then he plugs his audio gear into it. Sounds mighty fine. Clean, too.