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AC, DC, and Power Transmission

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Bjørn

Tue Mar 21 2006, 02:58AM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

100kV is no problem, 500 kV is common. You just stack a number of diodes or thyristors. You can buy completely standard thyristors that take 4.5kV at 3kA.

teravolt

Tue Mar 21 2006, 04:46AM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

AC is mutch more convertable than DC there fore more easaly transmited thanks to Tesla and Westing House at the turn of the century. Also Tesla worked for Edison who was a DC man so Tesla left and invented Tesla coils and poly phase circuits and the rest was history.

...

Tue Mar 21 2006, 05:26AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

there was a thread almost itentical to this on the old forum (but I can't find it).

I think it was going more on why do power companies use hv instead of using more copper and a lower voltage (copper is expensive), but a silimar thing goes here. It just costs too dang much to put dc-dc converters everywhere. There is an article arround refering to some huge ass vacuum tube that was supposed to able to do the converstion, but the article seemed to have a lot of bs it it.

I think they decided that at 60hz there was not much more corona losses than with dc, so they use it. I believe another reason that it caught on soo much was that it made for much better motor designs (you didn't have to use the brushed to reverse the polarity, so they last a lot longer, and you can get bonuses like them all beign syncronised).

IamSmooth

Wed Mar 22 2006, 05:50PM

Registered Member #190 Joined: Fri Feb 17 2006, 12:00AM
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Posts: 1567

I believe I started the thread on the last site. I was asking the same question.

Bjørn

Thu Mar 23 2006, 01:05AM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

The reason three phase AC was used over 100 years ago is that it was the only workable solution. Today DC is more efficient but conversion is very slow since fairly short term economical goals is the deciding factor.

Carbon_Rod

Thu Mar 23 2006, 02:02AM

Registered Member #65 Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155

AC based systems are popular and have well documented solutions. High power DC over long distances has numerous other issues most people have simply forgotten after the 1940s.

However I have seen off-the-grid homes that run a DC primary lighting and temperature control system with an AC-Inverter for traditional equipment. Itâ€™s just cheaper to build it this way sometimes and gets more efficiency out of the system by avoiding unnecessary power conversion & conditioning.

Both DC and AC generators have their advantages under certain conditions.

What is the power source and intended use (home or commercial)?

FastMHz

Fri Mar 24 2006, 11:35PM

Registered Member #179 Joined: Thu Feb 16 2006, 02:08AM
Location: Hagerstown, Maryland - Close to Prime Outlets
Posts: 287

Very interesting discussion. I always thought AC was better for long distance transmission than DC...at least, what's what they taught in school when you learned about the Edison vs Westinghouse battle. Aside from that, AC is good because of transformers and cheap induction motors whereas DC motors need to be brushed...OT: I wish we in the US had 240v standard in all wall outlets though instead of 120v.

vasil

Sat Mar 25 2006, 06:51AM

Registered Member #229 Joined: Tue Feb 21 2006, 07:33PM
Location: Romania
Posts: 506

AC is considered better because you can transform the electric parameters, cheap and easily, after your necesities, any place, anytime. AC transformers can work, in any wild conditions without much survey.

Carbon_Rod

Sat Mar 25 2006, 09:17AM

Registered Member #65 Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155

â€œDC motors need to be brushedâ€
If you meant a generator then this assertion is not completely true. It is common to have permanent magnets rotating around/between fixed coils. DC generators are easier for windmills as rpm fluctuations will not be as much an issue to remain usable. The ones that we evaluated had almost no ripple in the DC except a minor blip. I was rather amazed by the design as I was expecting to see a classic filter or regulator doing this -- yet it was without either. Most shocking was the price tagâ€¦ ouchâ€¦ =]

Alternators are perhaps the more popular devices these days (especially the heavy duty automotive units with external diode blocks.) The choice is easy if ones looking at buying 1 km of cheap drainage pipe or heavy copper wire. Often people try to get the generator as close to the dwelling as possible to reduce cost and maintenance issues. As it is much easier to regulate water flow it is often better for stable performance output. These are plentiful and cheapâ€¦ so often are the preferred devices for both commercial and residential use â€“ just donâ€™t forget to clean the silt trap once in awhile.

Ben

Sat Mar 25 2006, 09:29PM

Vigilatny
Registered Member #17 Joined: Thu Feb 02 2006, 02:47PM
Location: NL
Posts: 158

There are point to point DC transmission lines between Canada and the US.

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