Whole house "battery" wiring/power...

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krw wrote:

It wasn't my idea to start with you idiot, it was a discussion about possibilities. I'm so glad that a world leading expert such as yourself would chime in and share your dearth of knowledge. *snicker*
TDD
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On Sun, 04 Oct 2009 18:22:56 -0500, The Daring Dufas

<snip>
You sure "helped" it along.

It doesn't take a "world leading expert" to see that you're full of shit. Common sense is enough. Like I said earlier, try thinking for yourself sometime. Your neuron might be scared at first, but it'll calm down.
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And what would be the advantage? The 78xx series are linear regulators, they are in effect a regulated resistor that burns up the excess voltage in the form of heat. On top of that, they max out at 37V input at which point a substantial heatsink is required to dissipate the heat. The end result is FAR less efficient than even the lousy iron class II transformers found in most wall warts and small appliances.
You could use a switchmode regulator to get decent efficiency, but once you've gone that route, you may as well just use 120V or 240VAC since the additional components required are trivial.
Solar and wind power can easily integrate with the existing grid, with the additional advantage of being able to sell excess capacity back to the utility. The cost of the special inverter is low compared to what the panels cost, and dropping all the time. This proposed DC system is just reinventing the wheel with something inferior to what we already have.
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James Sweet wrote:

I was thinking about it as an off the grid system. I would imagine that a single high current DC to AC converter in the battery room putting out standard AC power to a home would be more practical than trying to reinvent all the appliances and gadgetry. Tesla won the battle for the power distribution system and I'm glad of it. There are those very high voltage DC power transmission lines. I'm going to have to read up on them and find out why they're using DC. It's been 20 years since I worked on any high voltage power distribution systems. Have you ever used a wooden hot stick? Make sure it's dry.
TDD
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wrote:

DC Power transmission lines are used to rid the line of skin effect and allow the entire cross section of the conductor to carry current. They are as yet only practical for long haul point to point circuits.
-- Tom Horne
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Tom Horne wrote:

That's what I read. My only experience with high voltage power transmission has been installing buried conduit, setting transformers, making connections and splices on 15kv coaxial underground cable. Of course there was all of the other wiring on the low voltage side of the transformer including the facilities wiring. What I find fascinating about the long haul high voltage DC power transmission systems has to do with the changes in technology over the years to handle the conversion of AC to DC then back again. The early mercury arc valve systems have got to be a sight to behold. I can imagine a mad scientist wearing super thick lensed glasses cackling in the background.
TDD
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Even a 5Kw 6 phase converter was a sight to see- looked like an octopus with glowing arms and a bright spot dancing on a dish of mercury. Seriously the advantages of DC transmission has relatively little to do with skin effect as conductors are typically ACSR with aluminum on the outside and steel inside- and, at these voltages are grouped in bundles. The size of the conductor has more to do with mechanical than electrical properties. DC transmission at high voltages is economical for long lines where the reduced cost of the line exceeds the added cost of the terminal equipment. There are also some other technical advantages . This breakeven point is at a much shorter distance for underground or underwater cable. DC back to back terminals are often used where frequency differences (e.g. in Japan with both 50 and 60 Hz systems) or stability concerns arise. They do have the disadvantage that reasonable and economic circuit breakers for DC don't exist and this means that the system is essentially point to point rather than through an interconnected grid. In addition, conversion from one voltage level to the next is bloody expensive, awkward and inefficient compared to the use of AC transformers. At low voltages, even for relatively short distances, DC is not a viable option.
--
Don Kelly
snipped-for-privacy@shawcross.ca
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Don Kelly wrote:

From my reading, the problem of capacitive reactance is also minimized with the DC transmission lines. When I was at Kwajalein Missile Range during the late 80's, I got the chance to explore the old phased array radar installation on Meck Island. It had a room we called the Frankenstein room which was the power supply for the old radar. From what I was told, the way they were able to make that monster scan, was to change the phase angle of the microwave beam. The Frankenstein room looked just like a prop from a science fiction movie. I wish I still had the pictures. Here's a link, look for Meck Island an you can see the big building in the upper right. There are two pictures, one showing a view of the missile silo or silos. I don't remember if there were two.
http://www.fas.org/spp/military/facility/kwaj.htm
TDD
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That too, and that is a major benefit. However, there is still a reactive problem at the receiving end where it is necessary to have the capacity to supply reactive. This will be dependent on load and the particular control of the system as a whole. For long lines this will be less than what would otherwise be needed to compensate for line capacitance.
--
Don Kelly
snipped-for-privacy@shawcross.ca
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YOU ARE SOUNDING LIKE AN IDIOT
HOW DO YOU SUUPLY REATIVE ?
YOU SHOULD COMMIT HAIKIRI
IT'S CALLED REACTANCE
AND I AM NOT GOING TO SHOW YOU HOW TO ACHIEVE THAT HERE NOR ANYWHERE ELSE
YOU WILL HAVE TO PAY THE PIPER DONKEY LIKE EVERYONE ELSE
OR JUST SHUT THE FLUX UP
PERMAMNENTLY !
I AM PROTEUS
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Proteus IIV wrote:
message

Uh, Pro, buddy, there is medication for your problem. Your county health department may be able to help you out with a psychiatric referral. FLNF
TDD
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The Daring Dufas wrote:

It is a particularly ignorant troll that infests alt.engineering.electrical.
Just ignore it like everyone else (except one of its equals).
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On Thu, 08 Oct 2009 23:50:40 -0500, The Daring Dufas
message

Are you kidding? We are talking about NYC here. To them, his nut case level is mild.
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On Thu, 8 Oct 2009 21:45:03 -0700 (PDT), Proteus IIV

Yeah, dipshit... That is the response to magnetic flux and work.
It is referred to by ALL of us in the industry, as a reactive load.
Go away, you know nothing twit.
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Only the Navy with their ships and submarines make use of DC well. That still doesn't mean that it wasn't one hell of a costly implementation.
DC is great... on anything miniature, like a scooter, or model airplane. :-]
Supplying DC feeds that can push as much power as we are used to with current AC settings in the home would not be easy, and homes are low consumption examples.
Even if we had compromised, and made AC to the pole, and DC into the house, the DC part has a lot of pain in the ass required maintenance that AC does not suffer from. Galvanic effects being the first one I think of.
OK, so we drop the HV down to about 600V on the local poles, and then we rectify that and feed the homes? Sounds like a very high maintainence/service oriented method.
Maybe if we could make a nice DC chopper that would let us step off DC highs and Gnd lows.. kind of a psuedo-alternation.
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Thats why Westinghouse beat Edison in the early days of deciding what electical distribution system to use, Westinghouse (scientist) wanted AC, Edison (who was more of an inventor than a scientist) would not let go of his prejudice for DC. I still have an old AC/DC radio from those days, when radios were sold to work on either distribution system.
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On Fri, 09 Oct 2009 09:04:47 -0700, windcrest wrote:

Hmm, that triggered a memory. I used to have an AC/DC one from the '60s - manual switch, and you could feed 12V DC in on the same power socket as AC. I doubt something like that would pass H+S these days, never mind the amount of people who'd try to feed it domestic AC with the switch on the DC setting and fry the thing ;)
cheers
Jules
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Jules wrote:

That's actually a bit different. The AC/DC radios he refers to use a transformerless power supply with the tube heaters wired in series. Yours likely wires the tube heaters in parallel with a vibrator to supply B+ to the plates when running from batteries.
The worst offenders for radios being plugged into the wrong voltage are 32V farm radios. The old 32VDC rural systems used the same plugs and receptacles as the 110VAC systems standard elsewhere, so it's common for someone unknowledgeable to plug a farm radio into a 120V receptacle and blow all the tube heaters.
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On Fri, 09 Oct 2009 23:49:42 -0700, James Sweet wrote:

For sure - it just stirred some braincells, that's all. The particular radio I remembered was an early (ish) transistor design - I think it may have been a Grundig, but I can't be certain now. The 12VDC ability was just to allow it to be run from a car battery whilst camping - I seem to recall my folks having a (black&white) TV that could run from a car battery, too, but I don't recall if it had a manual voltage switch like the radio did.
Just struck me as interesting that it was (in theory) so easy to plug in to AC (via the same connector) with the voltage on the wrong setting and presumably cook the thing!

Well, I grew up in the UK, and it's been 240VAC as standard over there in just about forever (well, near enough, Google tells me 1916) - although I think some DC via private generation in big, isolated houses survived into the 1920's. The historical picture in the US is a lot more diverse, it seems (and more interesting because of it :-)
cheers
Jules
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AC/DC radio sets were still commonly available into the 50s though, in the UK.
The Mullard valve amplifier circuits book, 2nd edition 1960, had a circuit for a 7W AC/DC amplifier, which was first published in 1957.
Stuart
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