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Old 06-11-2020, 12:57 PM
 
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Quote:
Originally Posted by Dane_in_LA View Post
FWIW, there was a move towards DC in large data centers. Imagine a few thousand racks, all loaded up with servers, switches, storage arrays and whatnot. Each of these device - and there are tens of thousands in a large data center - has one or more converters from 240V or 120V AC to (typically) 48V DC. This is tremendously inefficient, there's a huge heat loss, and - as anyone will tell you - the damn power supplies keep breaking.

What if - we instead put some huge converters to 48V DC in central spots and provided 48V directly to the eelctronics? It's readily agreed that it works, but adaptation has been very half-hearted - there's a definite "the devil I know" attitude. Which is too bad, it's elegant engineering.
What do you mean "a move toward DC"?


All IC data storage, in other words, the bistable devices that register 0 or 1, is DC. In fact, for all the hype surrounding the word "digital", at the bit level it's all analog; the only question is what's the voltage range for "1" and what's the voltage range for "0"?


No such thing as "a move to DC"; ever since Kilby came up with the silicon IC in the late 50s, ICs require DC. You can either have lots and lots of batteries, or use DC power supplies to rectify mains AC power to DC.


The reasons for using high voltage AC for long distance transmission of electric power are many and well documented ever since the early 20th century. If, on the other hand, you're talking about a single giant DC power supply for a server farm and feeding DC to the racks, I would guess the decision would be made on economics.
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Old 06-11-2020, 12:58 PM
 
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Originally Posted by timfountain View Post
220VAC, as used in all of Europe, makes a lot more sense than 120V. Power distribution is more efficient and you can get a lot more power out of a 220V wall socket. I wish the US would get with the 21st century and use a more efficient voltage in the home, apart from the range and clothes dryer....
Being first often means you're stuck with an inferior revision of technology. The US has been first in nearly everything, so we've ended up with some second-rate technologies embedded in our infrastructure.

There is no compelling reason to convert the US standard, nor even to implement 220 as an end-user standard in new construction. The trivial savings at the user level are dwarfed by the costs and complications. (And most power is transmitted at much higher voltages down to the neighborhood level.)
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Old 06-11-2020, 01:08 PM
 
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The vast majority of household power in the US comes in as 240/120 two phase anyway. Almost every house in the country has 240V service. You could rewire the house to run everything on 240, if you wanted to. But the general unavailability of 240V consumer goods in the US would make that a poor proposition. Given the small savings available by using slightly smaller gauge wire, and since few consumer appliances require more than a 15A circuit for 120V (approx. 1800W depending on the type of equipment), it's not worth it.
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Old 06-11-2020, 02:41 PM
 
Location: Portland, OR
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Originally Posted by Therblig View Post
Being first often means you're stuck with an inferior revision of technology. The US has been first in nearly everything, so we've ended up with some second-rate technologies embedded in our infrastructure.

There is no compelling reason to convert the US standard, nor even to implement 220 as an end-user standard in new construction. The trivial savings at the user level are dwarfed by the costs and complications. (And most power is transmitted at much higher voltages down to the neighborhood level.)

The US has been first at nearly everything? Come on now, be realistic. That statement is not even vaguely accurate. Not for so many things, electricity being one of them....



Specifically, the first place to be lit by an electrically operated light bulb? That would be the National Galley in London in 1850. Would you like some more firsts? Swan's house, in Low Fell, Gateshead (UK) was the world's first to have working light bulbs installed. The Lit & Phil Library in Newcastle (yes, that would be in the UK), was the first public room lit by electric light, and the Savoy Theatre (er, yes, UK again) was the first public building in the world lit entirely by electricity. The first central station providing public power was in Godalming, Surrey, (yikes, the UK again) in the autumn of 1881

Oh, and here's an interesting one - The first large scale central distribution supply plant was opened at Holborn Viaduct in London (oh no, the UK again) in 1882. Equipped with 1000 incandescent lightbulbs that replaced the older gas lighting, the station lit up Holborn Circus including the offices of the General Post Office and the famous City Temple church. The supply was a direct current at 110 V; due to power loss in the copper wires, this amounted to 100 V for the customer.



Note how they started at 110V DC, but soon realized the fallacy of that approach. So being first doesn't mean best, or that you can't change. When my father (who was from the UK) was in the Navy, the house he lived in Portsmouth, UK, was powered by 100V DC. This was in the 1950's....


Finally, I wasn't saying we SHOULD change to 220V in the US, I understand the impossibility of that. I was WISHING that we could change. Of course ever we know that 120V doesn't cut it, which is why we also have 220V for the bigger appliances in the home. My shop also has 220V for some of the machines out there.



Source - https://en.wikipedia.org/wiki/Electrification
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Old 06-11-2020, 04:24 PM
 
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Originally Posted by timfountain View Post
The US has been first at nearly everything? Come on now, be realistic.
Context is everything.

First, in almost every case you can name, in implementing modern technology on a wide scale — fastly and widely enough that when v2.0 came along, it was too late for change. So slower nations got the better tech, just had to wait for it.

And as pointed out, service to nearly every house in the US is 120/240. You want a 240 house? Knock yerself out. You will need to buy Euro/Aussie/commercial appliances (including countertop ones) and make sure all electronics have adaptable power supplies, but it's completely workable.
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Old 06-11-2020, 08:07 PM
 
Location: Portland, OR
1,223 posts, read 1,937,016 times
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Quote:
Originally Posted by Therblig View Post
Context is everything.

First, in almost every case you can name, in implementing modern technology on a wide scale — fastly and widely enough that when v2.0 came along, it was too late for change. So slower nations got the better tech, just had to wait for it.

And as pointed out, service to nearly every house in the US is 120/240. You want a 240 house? Knock yerself out. You will need to buy Euro/Aussie/commercial appliances (including countertop ones) and make sure all electronics have adaptable power supplies, but it's completely workable.

What are you blathering on about? I have a range and dryer, today, in my house, in the USA, that runs on 220V. 240V, yes, it's within 10% so no problems. At all.
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Old 06-11-2020, 09:39 PM
 
1,977 posts, read 503,478 times
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Quote:
Originally Posted by timfountain View Post
What are you blathering on about? I have a range and dryer, today, in my house, in the USA, that runs on 220V. 240V, yes, it's within 10% so no problems. At all.
Dishwasher? Washing machine? Toaster? Blender? Microwave? Electric blanket? Light bulbs?
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Old 06-14-2020, 07:08 AM
 
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Originally Posted by timfountain View Post
It is? News to me.... As a pilot. Yes, small general aviation aircraft may use 12V, but all commercial aircraft use 115v 400Hz ac. 400Hz because the higher frequency means that power converters can use smaller, lighter transformers.

Military aircraft use 115/400hz also. You DON'T want to get zapped by 115/400. 115/60 will give you a tingle. Had a friend on the flightline touch a switch that had been shorted out by 115/400 when he was squatting down over a test set. His leg muscles extended and he literally flew into the air. He spent two days in teh hospital and couldn't use hiw left hand (the one that had flipped the switch) for a week.


Also there are some 'wall warts' that put out ac power. Over the 35+ years I have been running and maintaing computer systems I have seen more varieties than I can remember. 5v DC, 6v DC, 9v DC, 12v DC, 19,5v DC (Dell laptops) are very common. There are also some that have connectors with multiple pins that put out several voltages.
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Old 06-14-2020, 07:25 AM
 
3,660 posts, read 3,705,405 times
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Quote:
Originally Posted by Therblig View Post
Context is everything.

First, in almost every case you can name, in implementing modern technology on a wide scale — fastly and widely enough that when v2.0 came along, it was too late for change. So slower nations got the better tech, just had to wait for it.

And as pointed out, service to nearly every house in the US is 120/240. You want a 240 house? Knock yerself out. You will need to buy Euro/Aussie/commercial appliances (including countertop ones) and make sure all electronics have adaptable power supplies, but it's completely workable.

Not always. clocks will not work properly. British 220 V systems run at 50 HZ not 60 HZ so clocks (which use frequency to maintain time) will be off. I worked for a company that built industrial systems for international customers and simple voltage transformers were not always sufficient for converting power. Also anything with a motor will be less efficent and possibly reduce service life.


Oh and DVD players made for Europe won't work with DVDs made for the U.S. Market because there are different encoding zones around the world.


It is also illegal (by code) too use outlets on the wrong voltage circuits. The plug not only tells what voltage the device is but what the maximum amperage is.
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Old 06-16-2020, 05:15 PM
 
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Quote:
Originally Posted by turf3 View Post
The vast majority of household power in the US comes in as 240/120 two phase anyway. Almost every house in the country has 240V service. You could rewire the house to run everything on 240, if you wanted to. But the general unavailability of 240V consumer goods in the US would make that a poor proposition. Given the small savings available by using slightly smaller gauge wire, and since few consumer appliances require more than a 15A circuit for 120V (approx. 1800W depending on the type of equipment), it's not worth it.
*sigh*

This thread has so many misconceptions that the class are deserving of a barely passing grade. MOST dwellings in the U.S. have SPLIT-phase entrances. There are exceptions, and your basic premise is correct, but this is a science forum.

Distribution lines are far above 220/240 volt single phase voltage. There is no need to change anything. Split phase, loosely, is when the full 220/240 volts is measured at the extremes of the output coil of the pig on a pole, BUT there is a center tap in the transformer that is at ground potential. That makes for a relatively safe home source of power.
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