and all use the same outlet plug. We have another 100 years
compromise with 100V/50Hz and both side can win and lose. 110V (or rounded to 100V) is much safer than 200V. We couldn't agree on this for the past 100 years. Hopefully, we could during the next 100 years. LOL.
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Just remember that it is rarely more than a few hundred feet to a transformer to a substantially voltage, like 4800 V or more. Nobody does anything but final distribution at 120/240 volts. High rise buildings take feed at "medium voltage" 1000 V to 50,000 V. In urban and suburban areas most of the real distribution is in the same range.
Fundamentally incorrect. Wind generators are induction machines not synchronous machines. Exite them and let the wind turn the shaft above synchronous speed, viola generator.
Ahem, NO! A sphere is the _minimum_ surface area shape. The enemy of power dissipation. The best is a thin flat long rectangle for maximum area with the same volume. The use of fans may require a wider thicker shape.
3.4" cube with 5 sides of useful area of 57.8 sq.in. I will slice it into
4 and line them up linearly long semi-wide thin shape 13.6" by 3.4" by
0.85" gives 42.24 + 22.78 + 5.69 totaling 70.71 sq.in. for 22+ percent more area. Get the picture yet?
Close. It is really a red herring as it is external to the target box design. The source must provide the required 450 V at 4.4 A and will have some rise at low loads (43 V). The box must deal with that.
"The load will be provided by an electronic load bank which can switch in and out a series of linear reactive, inductive and capacitive loads..."
So, if the load is resistive and the voltage meets the THD requirement, then the current also will and the requirement is unnecessary.
If, however, the load is highly reactive (e.g. capacitive), then the voltages at harmonic frequencies may need to be smaller than they would otherwise need to be, because of the requirement on the THD of the output current.
Ooops. Y'er right. Tradition is maintained, where I make at least one major screwup in such discussions. Maybe a short vacation will help. Thanks.
--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
Ummm... anything with an xformer inside, microwave oven, all wall wart chargers, stove with HF induction heater, refrigerator compressor motor, etc.
In the late 1970's, I got involved in wiring a geodesic dome. The builder wanted to run on battery power and had the same idea as what you're suggesting. Run everything on 120VDC and store power in 120VDC battery banks. Somehow, I got elected to make it all work. Don't ask about the planning department and inspectors.
The first problem was safety. Grabbing 120v AC will cause the muscles to shake rattle and roll. You'll get launched and probably slam into something. However, 120v DC will cause the muscles to contract and stay contracted as long as the power is applied. If you grab a live
120V DC wire, you probably won't be able to let go. That why 48VDC is considered the maximum "safe" DC voltage. This was duly noted by all involved and subsequently ignored.
Next were the simple things, like switches and sockets. With AC, the contacts will arc, and some metal might migrate from one contact to the other. With DC, they will weld together and/or produce a stalagmite shaped metal migration. When I tried conventional AC wall switches, they would weld closed after about 20 throws under load.
Wall outlets were even more fun. The power plug would be shoved into the wall jack and weld itself in place if under load. If I could manage to extract the plug, when I re-inserted it, there would often be a small explosion of hot metal as the migrated metal on the contacts would vaporize. Of course, everything worked just fine if I switched power or removed wall plugs with no load.
The winner of the DC maximum damage award was someones Model 77 Skil Saw. The motor is a series wound "universal motor" which should run nicely on DC. Just two problems... the brushes don't like arcing on DC, and the switch has the same problem as the AC wall switch running on DC. Predictably, the trigger switch welded itself shut, which gave the brushes enough time to arc and burn the fiber insulators. I had flames coming out the air vents and was holding a saw that I couldn't turn off without literally pulling the plug.
There were a few other horror stories, but we knew when to give up. Without replacing everything with DC rated devices, it wasn't going to happen. One of my solutions was to install a micro DC to AC inverter in each 4S wall outlet box. These would be switched on automatically when present with a load. I never took it past the idea stage.
So, you're welcome to try running various motors and heaters on 120V DC. They will probably work after a fashion or with DC style brushes made from alternating layers of graphite and carbon to reduce arcing.
Home Power Magazine once had many "conversion" articles, where off-grid home owners convert AC operated appliances and machines to DC. In many cases, such as a DC powered lawn mower or vacuum cleaner, it works just fine. I don't recall any that suggested powering the original AC motors with DC.
You're welcome to experience the aforementioned problems with that scheme by simply running any universal series wound motor on DC. I suspect your opinion might change after the experience.
--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
If by 400 V you are referring to 230/400 V wye/delta, the phase to neutral (and to ground) is 230 V, while the phase to phase voltage is
400 V. The main risk is the phase to ground (230 V) events, It would be extremely rare if one manages to touch two phases (400 V) simultaneously.
That is the consequence of using too low final distribution voltage, thus you have to have the final transformer in practically every pole. This also means that the medium voltage feed system to these transformers must be very long, having medium voltage feeds on nearly all streets.
In countries with higher final distribution voltages, the distance to the nearest transformer can be 400 to 1000 m and consequently less medium voltage feeds are needed to supply these transformers.
While some manufacturers still make exclusively asynchronous (induction) generators, some use synchronous generators with modulated rotor current so that 50/60 Hz can be extracted from the stator.
Direct drive (permanent magnet) generators run slowly, so an inverter is used to generate the final frequency.
The peak to peak voltage for 120 Vrms is 340 V so the DC-link voltage should be at least slightly higher than this to get clean sine wave. Using an H-bridge and you get 240 Vrms single phase.
A much higher voltage would mean more panels in series or panels with larger output voltage than the standard 12 V/panel.
At least the HTML specification was strange, it talks about 240 V 60 Hz. Is this a true single phase system or does this refer to the US
2x120 V system with a grounded center tap ?
In one point, there was a reference of two inputs and _three_ outputs. Are you required to bring out also a neutral connection on the AC side? How much unbalanced load (between 120 V and neutral) must be handled ? Is the midpoint of two capacitors across the DC input sufficient or do you have to use a third transistor pair to generate a stiff neutral ?
It looks to be an "emerging standard" for datacenters. I can quite understand it as a choice for datacenters - but what I would like to see is a low voltage DC standard for small or medium installations. 380V DC is probably great when you buy your computers by the rackfull - but I want to be able to buy a couple of 1U or 2U servers powered by something like 48V DC (the telecom standard) or 24V. I want to be able to buy a desktop and monitor that use the same DC levels with the same plugs - and I want to be able to choose a simple, external cheap AC-DC converter or to buy a UPS that handles it.
Yes, the LVD seems to have a very wide-ranging view on what is "low voltage". It was probably based on the voltages needed inside a CRT television, so that an unqualified user is allowed to handle a TV and plug it in.
But there are rules and regulations about wiring and installation of different voltages - without qualifications, I am not allowed to wire up
380 VDC (or 220 VAC), but I can do so for 48 VDC. That's not surprising
- you have to try hard to cause yourself damage with 48V, but 380 V is a lot more dangerous.
Basically, my wish is selfish - I want a 24 V or 48 V DC standard for computers of the type /I/ buy and administer, so that I can save about
20-30% of electricity in /my/ server room, and have smaller and simpler wiring and UPS's.
On a sunny day (Fri, 25 Jul 2014 12:45:49 +0200) it happened David Brown wrote in :
Yes single standard would be nice.
In the mean time I go from 12V DC to laptop charger input 18V for 5$25 cents inclusive shipping:
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An other on runs my HD Samsung monitor.
Step down is also cheap, 300W 9$30 cents free shipping::
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this charges my battery from the solar panel... never mind any optima, it has adjustable voltage and current limit.
And of course this one runs on it too, home made:
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I use that to charge all sort of batteries, and as lab supply.
**the soldering iron (electronic temperature controlled 230V 50 Hz) will need a re-design... for 12V** I am not sure what voltage the actual element runs on, We did use a Weller magnetstat on 24V DC battery? Or was it 12V? Its hard to beat the ebay prices, parts alone are more expensive. the shipping is more than that here locally! There is a lot of solar stuff on ebay. Import of solar panels has become problematic in Europe, they now add all sort of custom duties as market protection. So I bought that locally, just a sale, set me back about 80 Euro for a 100W 120x55 cm panel.
And I still have, from before the market protection, a lot of these from ebay, won a bid on:
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make your own panel...
So, single standard, well, anything that has a DC input goes ! It is interesting that my old Samsung monitor has a 230V AC input, but the new HD one has a 14 V DC input and and external adaptor... Could be a trend. The problem with 14V is that you actually, if your 12V battery is fully charged, need a SEPIC. OTOH there are tolerances...
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