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#4545 10/04/01 04:39 PM
A
Anonymous
Unregistered
>My vote would be similar to what is used on aircraft and shipboard systems--400 Hz 3 phase.
What is the voltage?

#4546 10/04/01 04:51 PM
Joined: Aug 2001
Posts: 7,520
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pauluk Offline OP
Member
Sparky:
The "Schuko" plug is probably the most widely used type in Europe - not just in Germany but also Austria, The Netherlands, Denmark, Sweden, Finland, Norway, and many more.
Its a round plug with two round pins for line and neutral and fits into a recessed receptacle. The ground connection is made by strips on the side of the plug which mate with two springs in the receptacle.
Have a look here for some pics: http://www.king-cord.com/ourpro/europe.html http://www.powercords.co.uk/pc107.htm
The only possible drawback to the plug is that it is reversible, so on a system with a grounded conductor it's no good where polarity is important. For the balanced system mentioned above, that wouldn't be a problem of course.
NJ:
As someone who has had to design and build power supplies to give outputs like 12V @ 30A+, I certainly agree that a 400Hz frequency would make things much easier in the filter capacitor department.
I take the point about 3-ph making it easier for motors as well. Most residential services in Continental Europe are 3-phase already (220/380V or 230/400V), although it seems to be done more for balancing single-phase loads than anything else.

Main GFI: OK if it's a higher-rated or time-delayed type solely to protect the panel and any sub-feeders and all branch circuits then have their own more sensitive GFI.

The systems here where the only GFI is the main are a nuisance. One ground fault anywhere and the whole lot goes off!

DS:
I think there are several different voltages used at 400Hz. Some of the ferries operating from the U.K. to Europe certainly use 220/380V systems.


[This message has been edited by pauluk (edited 10-04-2001).]

#4547 10/04/01 07:25 PM
Joined: Sep 2001
Posts: 806
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Member
Aircraft/shipboard power is generally 400Hz, 3 phase 200Y/115V. 28 VDC is very common for smaller loads, as well.

#4548 10/04/01 08:31 PM
A
Anonymous
Unregistered
>Aircraft/shipboard power is generally 400 Hz, 3 phase 200Y/115V.

Do you know the maximum ampacity of a circuit?

What I was thinking of is that the skin-effect is going to limit conductors of 400 Hz to about 0.260" diameter which is 2 AWG. Heavier conductors would have to be tremendously derated.

2 AWG would limit circuits to around 125 A. So we would have to be allowed to parallel them. The idea of having many of these paralleled is unappealing.

Perhaps the final transformer could be placed right ahead of or after the meter?

Equipment drawing over 100 A would have to run from a higher voltage - which isn't really a bad trade off.


[This message has been edited by Dspark (edited 10-04-2001).]

#4549 10/04/01 08:57 PM
Joined: Sep 2001
Posts: 806
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What formula/method are you using to calculate the skin depth/conductor size?

AFAIK, skin effect only becomes a real issue at tens/hundreds of kilohertz or higher. At these frequencies, conductors are often tubular copper (transmitter tuning coils, etc.) or a specially fabricated (and expensive) conductor material called "Litz Wire", which is a woven conductor comprised of hundreds of separately insulated strands, joined at the ends.

#4550 10/04/01 11:38 PM
A
Anonymous
Unregistered
>What formula/method are you using to calculate the skin depth/conductor size?
I would ask the same of you.

>AFAIK, skin effect only becomes a real issue at tens/hundreds of kilohertz or higher.
Not so.
At 60 Hz conductors are nearly maxed out where you see them end... 600 kcmils. You wouldn't want larger conductors since harmonic distortion has a swallower skin and can saturate the outside of a conductor.

Skin depth is inversely proportional to the square root of the frequency (7.75 * 7.75 = 60).

I use the simple formula 2.6 divided by the square root of the frequency. That gives the skin depth in inches. Multiply by two to get the diameter. Multiply by three to get the practical limit (>98% of current) - which works out to about a one inch diameter for pure copper.

But alas the discussion was about 400 Hz.
2.6 / 20 = 0.13. That's where I got 2 AWG. And since I note that only the outside surface of a conductor dissipates heat in long runs, the underutilized inner copper is of no use on continuous loads and larger conductors would required huge deratings.

This is still a lot thicker skin than the depths of just a few atoms seen when the frequency has a dozen digits rather than two or three.

Another way of thinking of it is that the skin at 60 Hz is only 1000 times thicker than at 60 MHz but 10,000 times thicker than at 6 GHz.

#4551 10/06/01 03:42 AM
Joined: Oct 2000
Posts: 2,723
Likes: 1
Broom Pusher and
Member
Simple!: Use Superconductive Elements!!!
I would promote the studies and experimentations of Superconduction Theories, then apply it to local - per occupancy power generation and systems.
Voltages and system types would be as described below under "Conventional" power systems.
Each occupancy would generate their own power, plus apply this to Superconductive circuit elements when possible.

Since that's simply a pipe dream / wishfull thinking, below is more understandable to actual human beings of planet earth - as opposed to mad quack scientists from other planets [like me [Linked Image]].

Here's my input for "Conventional" Power Systems [Linked Image]

Residential:
200 VAC 1 phase 3 wire. Center tap grounded at transformer, plus grounded conductor from center tap brought to all services, bonded to local GES and all EGCs, but not an active circuit conductor.
Voltage to ground will be 100 VAC max.
Incandescent lighting would [should] be Quartz Halogen, or if normal Tungsten fillament / Argon filled envelopes are used, 4 position fillament supports.
This system might eliminate the problems revolving around common grounded conductors which are active in circuits [noise, open "neutrals", "hot grounds", overloaded commons, etc.].

For Commercial projects:
200Y VAC 3 phase 4 wire Wye [with 115 VAC to ground, but no L-G circuits used] for small occupancies and normal low voltage circuitry.

480Y277 VAC 3 phase 4 wire for larger occupancies, with SDS for 200 VAC systems.

For Industrial projects [low voltage only]:
200, 480 or 600 VAC 3 phase systems.
Grounding the system is still up in the air to me. Pros and Cons to the methods of either type [would like some input from others on this one! I have several ideas either way]. Systems point more towards the Ungrounded types - but will still be grounded at the transformer.

As for Frequency, I would lean towards 400Hz. The Skin Effect problems could be adjusted by designing conductors differently [multiple and separate tubular layers, Aluminum materials, Heat sinked exterior insulations, insulation with low Capacitive losses - possibly with an inert layer of pure water].

With higher Frequencies, the Efficencies [Q, core loss, etc.] of Induction type machines would benifit. Transformers, Reactor-Core Ballasts and Induction Motors fall in this category.

Transmission circuits will be effected the most. Multiple stacked parallel feeders would be one possible remedy - although the extremely large Induction problem with these "series" feeders would create choking and heat problems.

Possible to Transmit at 60Hz, then Invert to 400Hz - or Transmit as DC, then Invert to 400HZ. Either one will have Inverter losses and wastes [Transistor heat, Rectifier losses, etc.].

About the only system type I would really like to see changed would be the ones where untrained personnel can easilly mess with things! These would be Residential and small Commercial occupancies.

Frequencies would be better up higher for the end user, but remain low for transmission.

I still would like to dump everything in favor of Superconductive Elements!!! That's my idea of the ultimate systems!

Scott SET - the soapbox is now empty and available for the next speaker [Linked Image]


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!
#4552 10/06/01 04:14 PM
Joined: Nov 2000
Posts: 2,236
Likes: 1
Member
Aw Man, I was gonna say something about Super Conductors earlier in this thread, but my ignorance of providing any detail to said system stopped me!

Do go on Scott!

(I hope y'all don't find it annoying that I edit almost every post, I'm a perfectionist sometimes...)

Q:

Assuming we can't make the entire system out of superconducting (i.e. "room temp") materials, where would the less exotic (sub 0ºC ) superconductors be best employed?

Liquid nitrogen in Xformers to cool them to superconducting temps (with appropriate materials)?

My "no holds barred" setup would begin with a Dyson Sphere\" ...

[Linked Image]

[This message has been edited by sparky66wv (edited 10-06-2001).]


-Virgil
Residential/Commercial Inspector
5 Star Inspections
Member IAEI
#4553 10/06/01 11:41 PM
Joined: Apr 2001
Posts: 21
M
Member
if and when i do decide to build a house, i want to have my own private transformer vault.. id have the PoCo provide a primary loop to my vault, 3ø 13.2kv ohh yeah.. then id set it up with a large 100 kva 480Y/277 transformer bank. id have all kinds of amp meters and power quality meters.. really high tech.. for the house, id step it down to 120Y208, and id bring 480 in to my shop, where all my power tools (milling machines etc) would be 480, all the shop lighting would be 277 too. id also step it down for small tool circuits... im happy with 60HZ, though i would like to see all recepticles be of the Hubbell twist lock type, and for the bigger plugs, the hubbell ones with the pins.. the huge ones.. lol id also have a stand by generator.. oh what fun id have if i won the lotto...

-m


Remember when you read my posts, im only 17, still learning... "Hey, its takes what it takes!"
#4554 10/07/01 06:06 AM
Joined: Aug 2001
Posts: 7,520
P
pauluk Offline OP
Member
Wow, I seem to have started something here! Superconducting liquid-nitrogen cooled conductors, Dyson Spheres..... Anyone for a Flash Gordon style energy beam??!!

A little off the subject of an ideal system, but a few years ago I heard about someone who lived in the shadow of a powerful shortwave broadcast transmitter (it was in Switzerland if I recall correctly). He fitted out his roof with dozens of coils and got enouh energy to run all his lighting on HF power. I suppose it was ideal from the point of view that once installed the cost per kWh was zero.

I've always liked the idea of having my own private transformer(s), though I'm not sure I'd go as far as having a 13.2kV (or British 11kV) supply!

My reasons are twofold.

First, the xfmr would provide a certain degree of isolation from all the harmonics, switching transients and other hash present on the public supply, especially if used in conjunction with suitable filters. This is important to me because of the sensitive radio equipment etc. I use at home.

Second,
I could arrange my neutral & grounding system as I want it, not as is dictated by the local conditions. This is tied in slightly with the above. I want a low-impedance ground path, but our PME system which ties the ground to the neutral which can introduce some of the same hash into the house grounding system.

In general, we have big xfmrs which feed a large number of houses - the two xfmrs in my location feed about 300 homes via a 3-ph network.

As far as I could make out from studying lines & poles while over there, you seem to use a greater quantity of smaller xfmrs for a given number of homes.

How would you feel about extending this to one house per xfmr throughout? Greater capital cost for equipment I guess, and possibly higher losses overall due to the smaller xfmrs, but good in other respects.

Hey, if the whole lot is going to be fed from energy from a Dyson Sphere, we'd have plenty to spare anyway, right?!

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