The Last DC Power Grid Shut Down in NYC 533
cell-block-9 writes "Today the last section of the old Edison DC power grid will be shut down in Manhattan. 'The last snip of Con Ed's direct current system will take place at 10 East 40th Street, near the Mid-Manhattan Library. That building, like the thousands of other direct current users that have been transitioned over the last several years, now has a converter installed on the premises that can take alternating electricity from the Con Ed power grid and adapt it on premises.' I guess Tesla finally won the argument."
Tesla won but... (Score:5, Insightful)
Re:Tesla won but... (Score:5, Informative)
Re:Tesla won but... (Score:5, Funny)
Good to see Wikipedia hold up under the mad scramble of 10,000 Slashdotters racing to be the first to update that entry to reflect today's event.
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Shesh...they have real servers and it's only read-only activity. As they are using MySQL, it's likely all cached hits to boot. As long as they have the bandwidth, it's likely a trivial load. It's not like
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I think your humor subsystem needs to be rebooted.
Re:Tesla won but... (Score:4, Funny)
Go Safe, Go Direct!
Re:Tesla won but... (Score:5, Insightful)
Most of us here on
Re:Tesla won but... (Score:5, Funny)
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Shot to the gonads perhaps?
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Re:Tesla won but... (Score:5, Funny)
Scale.. (Score:3, Insightful)
Re:DC vs AC (Score:5, Informative)
Do you have transmission lines that are three blocks in diameter? Then it's more efficient to convert at the source. What? You don't? Then I guess converting at the point of use is more efficient. Transporting the 5V and 12V levels that most consumer electronics use internally would be insane over more than a few feet because of voltage drop [wikipedia.org].
See Electric power transmission: History [wikipedia.org] for more information.
Re:DC vs AC (Score:5, Informative)
It would be more efficient to transmit DC, if we are talking about the same voltages. AC is impeded by inductance as well as resistance, so in addition to the inefficiencies of converting, you also are better off transmitting DC if it is the same voltage.
The trick is, transmitting at higher voltages is more efficient than transmitting the same power at lower voltage. This is because to send the same power at low voltage, you must send more current, and more current means more energy wasted as heat from the resistance of the line. So voltages from the generator are stepped way up before being transmitted.
And the reason AC won out is that it is much, much cheaper and easier to step up AC voltage (you just need a transformer, which is nothing but a couple coils of wire around an iron core) than to step up DC voltages (which requires a boost converter, which at its heart is a giant transistor [big enough to survive the voltages and currents of a power plant in this case] and a huge inductor [big fat coil of wire] along with timing and firing circuits to control the action of the transistor).
Boost converters are expensive, but over a long enough run of transmission line the advantages of DC over AC do make up the difference (as I recall, the break-even point is about a 400 mile long line). So you do find some long distance transmission lines that are DC. I know there is one out here in Sylmar, California that runs up to Washington state somewhere.
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With AC, the biggest concern is that you get it through either the heart or the brain, in most cases if you just touch the live wire in your house, you're most likely just going to get a ti
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The only way you are going to convert one DC voltage to a higher DC voltage is:
Re:DC vs AC - not true today (Score:5, Insightful)
Re:DC vs AC - not true today (Score:4, Insightful)
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I didn't say anything about the "power supply", I was talking about the Motherboard, which feeds electricity to that power hungry CPU, taking in the 5VDC at 20 Amps and convert it to 1.33 VDC at 60 amps per unit
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Although the UK and France both operate at a nominal 50Hz, it is normal for actual
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While there is no reason to replace a three phase AC motor with a DC motor, You might start powering variable-frequency drives directly from a DC distribution system.
Re:Circular gets the square (Score:4, Funny)
Re:Circular gets the square (Score:5, Funny)
Re:DC vs AC (Score:5, Informative)
DC has two main problems
1: it is a pain to voltage convert. Voltage conversion is pretty vital to our modern use of electricity, you don't want 11KV in your home but you don't want to be transmitting 240/415 three phase or worse 120/240 split phase any significant distance. You also want much lower voltages for loads of equipment.
For equipment power supplies it isn't so bad, they generally don't have particularlly high efficiancies anyway, they tend to run at fairly low power and they tend to be in a nice indoor environment but building a DC equivilent of a pole pig with similar efficiancy and reliability would get pretty expensive.
2: DC is a pain to switch, switches and breakers would have to be either much bigger or much more complex for a given DC voltage than for the same AC voltage (the zero crossings of AC tend to break arcs).
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Yes. They work by converting the DC to AC by switching, passing it through a transformer, then rectifying it back to DC. Look it up on Wikipedia.
...
So they're not DC transformers, they're DC-DC converters
(Why yes, as a matter of fact I do know a lot about AC to AC, AC to DC, DC to AC, and DC to DC power conversion - at least, up to the 10's of kilowatts level...)
Re:Tesla won but... (Score:5, Interesting)
uh (Score:3, Insightful)
people are fond of pointing out democracy's many failures too
but the real overriding realization with democracy and capitalism is that however much you think they suck, and they do suck in many ways, they are still better than any other system we can think of and have tried
so please, criticize capitalism. but unless you can enunciate a superior alternative, your criticism means absolutely nothing
Re:uh (Score:5, Insightful)
Re:uh (Score:5, Insightful)
Capitalism *IS* the best way ... (Score:3, Insightful)
Capitalism isn't the problem; thievery is.
If you're point had been that Tesla would be the rich, fat cat and that would be bad, then your moral compass would be off but at least your logic would be sound.
Re:uh (Score:5, Funny)
I'm sure Tesla wrote it down somewhere.
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Gotcha.
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The failures of democracy aren't democracy itself, but rather of the fact that our implementation of democracy is poor in that it doesn't actually give people the representation in government that they should have. Its too easy to get re-elected, its too hard to break into politics without vast amounts of cash and/or support from existing politicians, its too hard to remove someone who is doing a shitty job, its not nearly transparent enough, the
dude, calm down (Score:4, Insightful)
no one expects pure capitalism or pure democracy to ever be able to exist
i'm taking umbrage with radical fundamental departures from the core concepts: communism instead of capitalism, for example, or theocracy versus democracy
not capitalism, tweaked, or democracy, tweaked
the core ideas are always tweaked in one way or another to fit in the real world
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Too bad these aren't the real definitions. Look it up. Your definition of "democracy" is actually the definition of "direct democracy", while your definitino of "republic" is actually the definition of "indirect democracy" or "representative democracy". A republic can be a direct democracy, a representative democracy, or neithe
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That's a good argument against capitalism, where capital, if you have it, works for you. Start out with enough, and you can eat damn well on investments and compound interest without ever working.
And on the opposite side of the scale, if you can't work, you don't eat either.
Personally, I think effort-driven communism ("How much you eat depends on your effort to contribute") is theoretically the best system, but c
Re:Tesla won but... (Score:4, Insightful)
Much of the good ideas that really propel technology are that way. Capitalism rewards manipulative wheeler-dealers far more than creativity. It rewards those who can best exploit creative ideas, not make them.
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That's pretty typical. Example: who do you think of as the inventor of the telephone? Most people would say Alexander Graham Bell. But one could equally credit Antonio Meucci, Johann Philipp Reis, and Elisha Gray. Meucci especially. He beat Bell to it by over 20 years. But he was an Italian immigrant, spoke only poor English, and was effectively broke.
Example: A couple years ago, I independently came up with this:
http://appft1.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u= [uspto.gov]
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That's not to say that Edison cheating Tesla out of tens of thousands of dollars was a good thing, but Tesla survived that and ultimately ended up working with George Westinghouse. You seem to forget that
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Tesla died broke because he spent all his money trying to create a "wireless power distribution" that made no sense. If he had spent more time reading physics and less time building 100+ foot Tesla coils. Were some of his inventions stolen? Undoubtedly. But I think he has only himself to blame for losing all his money.
Except that now MIT has developed wireless power transmission [arstechnica.com]. Guess they need to learn physics as well, oh and stop faking having powered a light bulb wirelessly [mit.edu].
Falcon
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Most people answer with a blank stare whenever in mention the work of Tesla. While Edison's contribution is undeniable, he was more of a salesman than a scientist.
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If I ever make it to Belgrade, I'm planning to check out the Nikola Tesla Museum [tesla-museum.org].
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"When I hear the name 'Tesla,' I reach for my revolver."
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Re:Tesla won but... (Score:4, Funny)
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Idiot.
Re:ComEd not Con Ed (Score:4, Informative)
Advantages? (Score:2)
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Re:Advantages? (Score:5, Funny)
Re:Advantages? (Score:5, Funny)
Re:Advantages? (Score:5, Funny)
Re:Advantages? (Score:5, Informative)
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Re:Advantages? (Score:5, Informative)
There was an article on
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Yep, for ever expanding definitions of "short distances." High voltage high power DC silicon is getting better and cheaper, so we're already seeing a few long-haul DC lines where the reduced radiative losses and increased carrying ability of the cables makes it more efficient. On the other end, DC converters are becoming ubiquitous inside electronics. Google wants to standardize on only one voltage (12V) coming from your computer's PSU, and anything that wants another voltage just has its own converter.
Re:Advantages? (Score:5, Funny)
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Do you post from a DSL line?
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Re:Advantages? (Score:5, Informative)
Personal identification number number?
Direct current current?
See wiki [wikipedia.org].
Re:Advantages? (Score:5, Interesting)
Another difference is that getting shocked by DC tends to be slightly less dangerous than the same shock from AC. A 110V DC shock to bare (unbroken) skin is is quite mild feeling, where most people in the US have found (sometime or other) than 110V AC is fairly uncomfortable, though usually not particularly dangerous (i.e. for every person who dies of electrocution, an unknown but certainly large number of others are shocked with no real consequence beyond surprise and discomfort).
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AC power has one HUGE advantage and maybe other smaller ones. You can cheaply and easily step the voltage up and down. Stepping A DC voltage up and down is much more complex. DC to DC converters are getting cheaper and better to the point that people are proposing and building high voltage DC power distribution systems.
Re:Advantages? (Score:4, Informative)
Re:Advantages? (Score:4, Interesting)
That's as maybe (Score:5, Funny)
What about local (solar/wind/geothermal) power? (Score:2)
A powerful, electrifying news story (Score:5, Funny)
DC still in use (Score:3, Informative)
Re:A powerful, electrifying news story (Score:5, Funny)
You're obviously not aware of current events.
Signed,
AC
(How apropos: my catchpa is betatron [wikipedia.org]
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What do they use in Washington?
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I tend to agree. If I find something worthy of using a mod point for any reason, then I think it should be reflected in that user's karma. Why discriminate against humor?
Re:MOD PARENT "FUNNY"! (Score:5, Funny)
I tend to agree. If I find something worthy of using a mod point for any reason, then I think it should be reflected in that user's karma. Why discriminate against humor?
Because Slashdot is intended to generate informative and insightful discussion rather than humor?
Deliberately using the wrong category when moderating reduces the readers ability to filter the posts in the way that they want. Moderators are supposed to categorize posts. They are not supposed to care about the karma of the authors.
DC to AC converter inside? (Score:3, Insightful)
a few blocks from where tesla lost the argument (Score:2)
the new yorker hotel is on 34th and 8th. the final dc site near the midtown library is on 40th and 5th
unfortunately, business acumen and scientific genius do not necessarily go hand in hand
sad [wikipedia.org]
Is there 600VDC in Boston? (Score:4, Informative)
Later elevators still used 600VDC but used a dynamotor; that whine you used to hear when you pressed an elevator button elsewhere was the dynamotor starting, to convert to 600VDC from the 120VAC line current. Eventually, elevator manufacturers stopped using it, but when you hear that whine in a medium-old elevator, you know what is is.
Re:Is there 600VDC in Boston? (Score:5, Insightful)
Later elevators still used 600VDC but used a dynamotor
What you're hearing is not a dynamotor, but something called a Ward Leonard drive. It's a fixed-speed motor driving a generator, but its purpose is speed control. The field current of the generator, which is small, is adjusted to control the larger output of the generator. The variable output of the generator then drives the elevator motor. The Ward Leonard drive is thus a big power amplifier. Until power semiconductors got big enough, which wasn't really until the 1980s, this was the most effective way to smoothly speed-control large motors.
A dynamotor has a common field for the input and output sides, but a Ward Leonard drive does not.
Incidentally, the Wikipedia article in Ward Leonard drives is bogus. Here's a better reference. [google.com]
The article was wrong about subways (Score:5, Informative)
AC's advantage of high voltage transmission doesn't apply to subways as 1200V seems to be the limit for third rail. 2400VDC was tried in 1915 on the Michigan Railways (an electric interurban in central Michigan) with abysmal results - the voltage was changed to 1200V within a year of the initial installation.
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Subways (and the like) are unique because the transmission line is also your final output/usage point. Yo
DC, actually, nowadays makes a lot of sense. (Score:5, Interesting)
Said all that however, high-voltage DC, a transport technology that starts to make sense nowadays, thanks to high-power solid-state switching elements, has many advantages over AC in terms of losses and cable utilization. You can transport more energy via DC than AC, across the same thickness cable. And you have practically no losses due to parasitic capacitances and inductances. The corona effect is much easier to control, too.
So, if I was forced at gunpoint to make a prediction for the electricity transportation in 150 years from now, I'd say hihg-voltage DC.
Easier to feed back into? (Score:3, Insightful)
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So what you need to achieve is high voltage. But in the past, that wasn't possible with DC, because there was no _efficient_ way to transform the voltage/current aspect of the power line for DC, only for AC.
Progress. (Score:5, Interesting)
If you want a feel of old DC equipment from the days when if you wanted power you had to make your own, head down to Pratt Institute (located in Brooklyn on Willoughby ave. and Hall st.). They still have 3 steam driven reciprocating piston dynamos built by Ames Iron Works. They work but are only for show. And to top it off they also have a steam turbine dynamo all of which is hooked to a large open marble panel board with knife switches, carbon arc circuit breakers and blade fuses. The panel is still live on the AC side. The Motor generator I mentioned is still there. You can go down to the Pratt engine room and get a tour from Conrad Milster, the Chief engineer who keeps the place running. The large 1930's brick steam boiler still heats the campus and the surrounding neighborhood. The site is an IEEE land mark and walking down there is like going back in time, a real treat.
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It's been pushed to its absolute limits in terms of age and longevity. The subways have served us well, but it's only been in the last few years that we've stopped neglecting them, and replacing outdated/dangerous systems with more efficient modern counterparts. (There was also the issue that the only people who knew how to service some of the archaic equipment that the MTA was running had been dead for at least 20 years)
The pum
Misinformation (Score:5, Informative)
Over the short-haul, this is good since losses are primarily resistive and losses are related to the amount of current flowing in the conductors. Power in my neighborhood is delivered at 12,000V and down-converted to 120/240 by transformers located every few houses. Delivering power at 120V would require 100 times the current and massively larger conductors. Once it gets to my house, with the exception of some motors and some lights, everything from TV to stereo to computer ends up having to take that power and reconvert it to DC.
But AC has far higher losses through capacitance and inductance which become severe over long distances. This is why some current and other planned long-haul transmission routes use DC. A good example of this is the 800-kilovolt DC line that connects into the Sylmar Terminal Station near Los Angeles.
Apparently, the use of Extra High Voltage DC is being proposed for a number of new long-haul transmission systems and it is the high losses incurred by AC over long distances that is driving the use of DC.
DC transmissions still exists as HVDC (Score:4, Informative)
There are some advantages (source: http://en.wikipedia.org/wiki/HVDC#Advantages_of_HVDC_over_AC_transmission [wikipedia.org]):
Here's a list of notable places that use it:
http://en.wikipedia.org/wiki/List_of_HVDC_projects [wikipedia.org]
Interesting book to read (Score:3, Interesting)
The Backstory (Score:4, Informative)
I hope... (Score:4, Funny)
how does that even work? (Score:3, Interesting)
Mercury Arc Rectifiers (Score:5, Interesting)
I think the most beautiful piece of old AC to DC conversion technology was the mercury arc rectifier...apparently these devices were still used on some branches of the NYC subway until late in the 20th century. A video of one in operation can be seen at http://www.youtube.com/watch?v=Rt-a8fxgtno [youtube.com]
A center-tapped transformer was connected to two anodes to form a full-wave rectifier(some had more anodes and were used for 3 phase power), and a pool of liquid mercury was used as the cathode material which would form an arc only if the anode was positive. A keep-alive electrode kept the interior full of vaporized mercury to facilitate the discharge. I'd sure like to have my own. Unfortunately an average sized mercury arc rectifier contains around 2 pounds of liquid mercury, so if it ever broke, my neighborhood would have to be decontaminated, my home razed to the ground, and the rubble buried in a concrete encasement.
Re:Yep, Tesla won alright (Score:5, Informative)
http://en.wikipedia.org/wiki/General_Electric [wikipedia.org]
GE's divisions include GE Commercial Finance, GE Industrial, GE Infrastructure (including GE-Aviation and Smiths Aerospace), GE Consumer Finance, GE Healthcare, and NBC Universal, an entertainment company.
Re:I know everything technically is DC.. (Score:4, Informative)