110v in US but 220v elsewhere. Why?

[lago]

I think about this whenever we travel outside the US. Why is the US at 110v and most of the rest of the world using 220v?

Who made that decision and why?


TIA
Ken

[linear]

You lose less power heating up the wires @ 220V.

Power loss in the wires due to heat is (I^2)*R, where R depends on length and diameter and material of the wire.

So to deliver 220W to a motor (say) in the US it takes 2A @ 110V, while it takes just 1A @ 220V in Europe. Since loss due to heating is proportional as the square of current, you lose four times as much power in heating the wire in the US, all things equal (which they aren't--aluminum wire is more common there than here).

[peel]

The Straight Dope

This popped up in a weekly e-mail from one of my all time favorite sites lately.

If you've never been to straightdope.com or read any of Cecil Adams' Straight Dope books you're missing out. Anyway, he claims it mainly comes down to the fact that the US was the leader in electricity and paid the price in picking the wrong (i.e. - more inefficient as shown above) standard.

Here's the full link but be careful, this site can suck you in:

http://www.straightdope.com/classics/a3_292.html

-peel

[Tom Slick]

there was a great amount of politics involved when the US was getting wired. we could have ended up running DC if Westinghouse wouldn't have had his way. if it were up to me everything would run on 480 3 phase or its derivatives.

another oddity is that we run at 60hz and most places run at 50hz.

[LCHIEN]

The choice of line voltage and line frequency is somewhat arbitrary.
Besides voltage differences there is also a frequency difference.

Early electricity distribution in the US (and first in the world) had competing standards of AC and DC, with Edison championing DC and chiefly concerned with selling lights and the more farsighted Westinghouse/Tesla pushing for AC. The benefits of AC eventually won as it should have because it permits easy shifting of voltage up and down using transformers (High voltage for transmission) and lower voltages for commercial and residential use. AC also allowed induction motors, very simple and reliable.

The correct frequency was somewhere around 50-60 Hz (cycles per second) because much lower than that the transformers get too big and much higher than that the line losses in transmission become too large. So the US got 60 Hz and most of the other world to be different got 50 Hz. There are still some odd voltages and frequencies in a few areas that did not get standardized, like the pumps in New Orleans installed around 1900 are weird.

The home voltage started around 100VDC (Edison) and so the AC voltage was also close at 110 V. For larger power applications 220, 440, etc. was also made available and was relatively easy with transformer taps. I think the 100V was chosen to limit the lethality from electrocution so most US residential use and appliances started 110 as the standard. Europe came later and they went 220 for a little better wiring efficiency and more umph, it was only slightly more lethal, the US having found that 110 was pretty lethal anyway (I wonder what the relative electrocution rate is between 110V societies and 120V societies).

The US system offers split 220 into two 110 circuits with neutral. Europe offers simply 220 with no neutral. So in a way its not that different, with basically 220V being delivered to residences.

Induction motors turn at multiples of the line frequency less some slippage (5-10% depeending upon load). So motorized equipment designed for 50 Hz will operate at differnet speeds, about 1.2 X faster in the US. Those with pulleys can be fixed (change a pulley diameter by 5/6), those with direct drive can't.

So the choice of actual voltage and frequency was kind of an arbitrary thing with different standards popping up on differnet parts of the world and some large groups causing these disparate standards to be retained.

[Slik Geek]

The U.S. voltage standard has its advantages

I actually think that the United States voltage standard is preferable. Plus, it has advantages that are just now becoming evident. Here are my reasons for prefering the US system:

Frequency
Magnetics size
60 Hz allows smaller magnetic cores on line frequency inductors and transformers than 50Hz. The US standard allows construction that uses less material (lower cost, less environmental impact). This is most significant in higher power magnetics.

Natural frequency?
60 Hz seems more "natural". (This is lame, I know). In the US, line frequency is 1/60 of a second. A second is 1/60 of a minute. A minute is 1/60 of an hour.

Voltage
Safety / Insulation
The lower voltage US standard requires less insulation for safety. This is a minor point, invisible to most people. To equipment designers, the 220V/240V system requires more space and more costly insulation systems in electronics as well as transformer construction. For relatively low power systems (most home electronics, for example), 120V is high enough for power distribution efficiency, but low enough to not require as much insulation.

Wiring flexibility
I agree that 220V/240V has less resistive losses. I would counter that in the US, with the two-phase (120V/240V) standard wiring in homes and the three-phase (120V/208V) in commercial/industrial locations, one can achieve similar efficiencies for high current loads by a simple choice of how an outlet is wired. My shop has 120V and 240V outlets, depending on the type of equipment it powers. There are limitations on this in terms of equipment availability, so this optimization isn't always possible in the US. I believe that this flexibility is becoming more useful - see below.

Switch-mode power conversion efficiency
The biggest advantage, however, is just now coming of age as the number of relatively low-power electronics devices in homes has sharply increased, and concerns about power conversion efficiency are becoming paramount. The days of line frequency transformers are numbered, as an increasing number of devices use switching power converters.

In my experience, electronics switching power supplies are more efficient at 120V than at 240V. At low power levels, switching losses dominate over resistive losses. This results in a switching power supply consuming greater VA (reactive power) when operating at 240V than at 120V. The difference is only 5 to 10% in most instances, but when consider on a grand scale, a 5% reduction in the power requirement in the US, for example, means we need roughly 500 fewer generating plants when these switching power supplies use 120V instead of 240V (out of a total of about 10,000).

I expect that Loring will have comments to add...

[430752]

everything you needed to know....

.... but didn't really need to know! Thanks for the lesson. And I'm staying away from that straight dope site, used to read his articles, once a week wAS enough in local paper. Can't imagine how much time I can waste with a whole website full of 'em!

Curt J.

[sacherjj]

I thought it was a method of telling the serious (220V) woodworkers from the hacks (110V, like me.)

[Richard in Smithville]

This is what happened when an outlet in my daughters room grounded on a screw(taped to the top of the outlet) that worked itself loose in the wall.

I'm glad that it was only 110. But I do know that the breakers work!

[leehljp]

Loring hit the nail on the head with his insights. I see MUCH more energy efficiency here in Japan where we have a 100V system and 50 cycle in half the country and 60 in the other half.

I can't believe the cooling and heating capacity of even 100V wall unit air conditioiner/heaters. Washers and especially 100V dryers. Fluorescent light bulbs (not tubes) in Cool white, Day Light, Warm (and other) have been available here much longer than in the US. Last year when in the States for almost a year, I searched every light store and big box store I could think of in the Memphis area looking for the cool white and daylight fluorescent light bults that looked like a "light bulb". No go. Only "warm" or the non light bulb shapped.

The point is that "low power" is coming and 240/220/200V is about to become obsolete as a necessity to the average consumer and home. Japan and Korea are leading the way in this and are several years ahead of the US. Low power consumer, home use and small shop use electronics are on their way.

Loring: Switch-mode power conversion efficiency
The biggest advantage, however, is just now coming of age as the number of relatively low-power electronics devices in homes has sharply increased, and concerns about power conversion efficiency are becoming paramount. The days of line frequency transformers are numbered, as an increasing number of devices use switching power converters.