Woah!

I just got a 1 MB PDF file. Opening it makes my poor little 1.5 GHz 
Athlon cry. Printing it resulted in a dense tangle of lines that was 
beyong legibility. Checking the PDF properties, I see it's designed for...

...are you sitting down?...


A0 paper.

As in, the largest standardised paper size that exists, at more than a 
meter wide. (2.5 feet by 4 feet, roughly.)

The writing was hopelessly small. (If you ask Word to print some 2 pt 
text on an A4 sheet, that's roughly how big. Although I notice it's a 
particularly bland sans serif typeface that only appears to contain 
uppercase.)

Interestingly, I asked the computer to print it again at A3 size (we 
have *one* printer that can do this), and the lines all stayed the same 
thickness; they're just further apart now. It's still extremely cramped, 
but it's vaguely readable. (I notice fairly extreme aliasing due to the 
fact that all the lines are very slightly off axis.)

This plan contains an entire zoo of curios symbols - but unlike the 
previous plan, there's a key explaining what they all are:

   (Semicircle with line)
   FLUSH SINGLE 13A SWITCHED SOCKET OUTLET

   (Filled semicircle with line)
   FLUSH TWIN 13A SWITCHED SOCKET OUTLET

   (Half-filled semicircle with line)
   13 SWITCHED FUSED CONNECTION UNIT

   (Half-filled semicircle with line inside dashed box with "FCU")
   13A SWITCHED FUSED CONNECTION UNIT AT HIGH LEVEL ABOVE CEILING FOR 
FAN COIL UNIT

   (Half-filled semicircle with line inside dashed box with "HVA")
   13A SWITCHED FUSED CONNECTION UNIT AT HIGH LEVEL ABOVE CEILING FOR 
HVAC CONTROLS

   (Semicircle with cross)
   16A SPN+E SINGLE PHASE NEUTRAL & EARTH INDUSTRIAL UNSWITCHED SOCKET 
OUTLET MK COMMANDO OR EQUAL & APPROVED

   (Box with "R")
   SP&N ISOLATOR - R DENOTED RATING OF DEVICE

   (Half-filled box with "R")
   TP&N ISOLATOR - R DENOTES RATING OF DEVICE

   (Box with "PP")
   POWER POLE C/W 4XSINGLE 13A SWITCHED SOCKET OUTLETS AND 4XRJ45 DATA 
OUTLETS

   (Dashed line)
   3 COMPARTMENT DADO TRUNKING INSTALLED BELOW WINDOW CILL

   (Box with "FB")
   3 COMPARTMENT FLOOR BOX C/E 2xTWIN 13A SWITCHED OUTLETS & 4xRF45 DATA 
OUTLETS. 3 METRE UNFUSED 32A TAP OFF UNITS & FLEXIBLE CONNECTION

   (Unequal-dashed line with crossed box)
   63A UNDERFLOOR BUSBAR WITH END FEED UNIT

   (Rectangle with diagnol hatching)
   200mm BASKET TRAY - ABOV CEIL[cut off printout]

   (Rectangle with dots)
   200mm BASKET TRAY - IN FLOOR VO[cut off printout]

   (Filled triangle)
   RJ45 OUTLET WIRED BACK TO PATCH PANEL IN COMMS ROOM TESTED AND LABELLED

   (Filled square with white triangle)
   ENTRANCE INTERCOM AND DOOR RELEASE

This entire text takes up less than 3 inches of paper.

(Woah - 63A? o_O Anybody know what thickness of copper it takes to 
handle that kind of currentl? That's gotta be more like a girder than a 
wire!)

Inspecting the plan itself, I see an underfloor tray leading from that 
curiosly non-square "riser cupboard" to all of the ofice spaces and my 
server room. I then see an above-ceiling tray running from the server 
room to all the lab spaces.

The office spaces are liberally littered with floor boxes, the lab 
office has floor boxes and a generous sprinskling of wall-mounted power 
and data sockets, and the lab is positively *encrusted* with power and 
data sockets on every available vertical surface. (Even the support 
girders holding the roof up!)

Checking the other data on the plan, I find this:

   TITLE
   Ground Floor Office B
   Small Power & Ancillery Services

   DRAWN BY
   KB

   APPROVED
   RB

   DATE DRAWN
   27-09-07

   SCALE
   1/50 @ A0

   DRAWING NUMBER
   1001/E003 B

(All of which is really *extremely* hard to read. The typeface is fairly 
big, but seems to be boldface or something. Almost no whitespace inside 
letters like "O"...)

Nice of them to include the paper size this time! (It makes a bit of a 
difference.) So, printed at A3, this should be... hmm... 1:400. Ouch!

So, given that it's 1:400, that means we've got power and data sockets 
every... uh... 2 meters, roughly. On almost every internal wall in the 
lab. And floor boxes every 4 meters everywhere else. Wow.

Oh look, there's a box on the back wall marked

   GENERATOR INPUT SOCKET

Since we store stuff that has to be kept frozen, a power cut is a fairly 
major event. Our customers won't be too pleased if their $80 million 
project has to be restarted from scratch because the stuff melted! So in 
the event of a power cut, a big truck comes along and dumps a huge lump 
of pig iron labelled "CAT POWER" outside our building, with a 
ridiculously huge cable and a comically over-sized plug on the end. 
(Seriously, the cable is thicker than some tree trunks!)

There's A LOT of over-printed text, but it seems that the individual 
sockets don't have unique numbers. ;-)

It's really quite confusing trying to reed this plan - the trunking 
stands out much more than the actual walls. I keep thinking the wire 
trays are the walls, and the walls are wire trays! LOL.

Post a reply to this message

> (Woah - 63A? o_O Anybody know what thickness of copper it takes to handle 
> that kind of currentl? That's gotta be more like a girder than a wire!)

Roughly double your standard 13A cable would do...  Look at the cable going 
to the starter motor on your car, that's usually 100A or so.

> It's really quite confusing trying to reed this plan - the trunking stands 
> out much more than the actual walls. I keep thinking the wire trays are 
> the walls, and the walls are wire trays! LOL.

Can't you print it out tiled, ie 8 A3 sheets (or however many it is) then 
just put them together?

Post a reply to this message

scott wrote:
>> (Woah - 63A? o_O Anybody know what thickness of copper it takes to 
>> handle that kind of currentl? That's gotta be more like a girder than 
>> a wire!)
> 
> Roughly double your standard 13A cable would do...  Look at the cable 
> going to the starter motor on your car, that's usually 100A or so.

1. A car runs on 12V electrics, not 250V. Does that make a difference?

2. Is maximum load proportional to diameter or cross section area? (The 
latter is quadratically propertional to diameter.)

> Can't you print it out tiled, ie 8 A3 sheets (or however many it is) 
> then just put them together?

Well, in principle yes. In practice, I very much doubt you'd ever get 
the pieces to line up properly. (Ever notice how map books *always* put 
the place you want to look at in the crease?) Plus I'm having enough 
trouble finding somewhere to put an A3 printout without it getting 
crinkled up... :-S

Apparently the planners have access to an A0 printer. I don't even want 
to imagine what that must cost... ;-)

Post a reply to this message

Invisible wrote:
> scott wrote:
>>> (Woah - 63A? o_O Anybody know what thickness of copper it takes to 
>>> handle that kind of currentl? That's gotta be more like a girder than 
>>> a wire!)
>>
>> Roughly double your standard 13A cable would do...  Look at the cable 
>> going to the starter motor on your car, that's usually 100A or so.
> 
> 1. A car runs on 12V electrics, not 250V. Does that make a difference?
> 
> 2. Is maximum load proportional to diameter or cross section area? (The 
> latter is quadratically propertional to diameter.)

Hmmm... Here's some info:

http://www.powerstream.com/Wire_Size.htm
http://www.epanorama.net/documents/wiring/wire_resistance.html

According to the one site, 6 AWG wire would be enough. Next size up if 
over 100 ft. :)

Post a reply to this message

Invisible wrote:
> scott wrote:
>>> (Woah - 63A? o_O Anybody know what thickness of copper it takes to 
>>> handle that kind of currentl? That's gotta be more like a girder than 
>>> a wire!)
>>
>> Roughly double your standard 13A cable would do...  Look at the cable 
>> going to the starter motor on your car, that's usually 100A or so.
> 
> 1. A car runs on 12V electrics, not 250V. Does that make a difference?
> 
> 2. Is maximum load proportional to diameter or cross section area? (The 
> latter is quadratically propertional to diameter.)
> 
>> Can't you print it out tiled, ie 8 A3 sheets (or however many it is) 
>> then just put them together?
> 
> Well, in principle yes. In practice, I very much doubt you'd ever get 
> the pieces to line up properly. (Ever notice how map books *always* put 
> the place you want to look at in the crease?) Plus I'm having enough 
> trouble finding somewhere to put an A3 printout without it getting 
> crinkled up... :-S
> 
> Apparently the planners have access to an A0 printer. I don't even want 
> to imagine what that must cost... ;-)


They are not too bad - at least the cheaper ones.  We have a 'plotter' 
that prints 2'x3' pretty easily.  The paper is on a roll that is 3' wide 
and like 50' long.

If you need to get it printed look at local copy centers - they might be 
able to help.  Some engineering shops (that sell stuff) might be able to 
help you out as well.

But then again, maybe you are expected to look at your tiny screen and 
figure everything that you need in your head.  After all, pencils cost 
money as well..


Tom

Post a reply to this message

Mike Raiford wrote:
> Invisible wrote:
>> scott wrote:
>>>> (Woah - 63A? o_O Anybody know what thickness of copper it takes to 
>>>> handle that kind of currentl? That's gotta be more like a girder 
>>>> than a wire!)
>>>
>>> Roughly double your standard 13A cable would do...  Look at the cable 
>>> going to the starter motor on your car, that's usually 100A or so.
>>
>> 1. A car runs on 12V electrics, not 250V. Does that make a difference?
>>
>> 2. Is maximum load proportional to diameter or cross section area? 
>> (The latter is quadratically propertional to diameter.)
> 
> Hmmm... Here's some info:
> 
> http://www.powerstream.com/Wire_Size.htm
> http://www.epanorama.net/documents/wiring/wire_resistance.html
> 
> According to the one site, 6 AWG wire would be enough. Next size up if 
> over 100 ft. :)

I'd say 3 AWG - but either way, it's less than 1 cm thick.

Like I said, when they hook up the external generator, it comes with a 
cable well over 10 cm thick (!)

Post a reply to this message

Tom Austin wrote:
> Invisible wrote:
>> Apparently the planners have access to an A0 printer. I don't even 
>> want to imagine what that must cost... ;-)
> 
> 
> They are not too bad - at least the cheaper ones.  We have a 'plotter' 
> that prints 2'x3' pretty easily.  The paper is on a roll that is 3' wide 
> and like 50' long.

I used to own an old HP line plotter. (Do they still make those?) It 
seems amazingly fast - until you actually try to plot anything of any 
real complexity, and then suddenly it seems absurdly slow...

> If you need to get it printed look at local copy centers - they might be 
> able to help.  Some engineering shops (that sell stuff) might be able to 
> help you out as well.

Nah. If I was that bothered, I'm sure the planners themselves can supply 
a printout. (Indeed, it seems to be easy to get prints, and 
near-impossible to get electronic copies...)

Post a reply to this message

Invisible <voi### [at] devnull> wrote:
> I'd say 3 AWG - but either way, it's less than 1 cm thick.
>
> Like I said, when they hook up the external generator, it comes with a
> cable well over 10 cm thick (!)

A lot of that thickness will be insulation, shielding and armor.

Stephen

Post a reply to this message

Stephen wrote:
> Invisible <voi### [at] devnull> wrote:
>> I'd say 3 AWG - but either way, it's less than 1 cm thick.
>>
>> Like I said, when they hook up the external generator, it comes with a
>> cable well over 10 cm thick (!)
> 
> A lot of that thickness will be insulation, shielding and armor.

Probably.

The plug is physically larger than my head. The whole contraption looks 
like a giant's plaything has fallen out of the sky or something...

Post a reply to this message

And lo on Fri, 09 Nov 2007 11:44:37 -0000, Invisible <voi### [at] devnull> did  
spake, saying:

> Since we store stuff that has to be kept frozen, a power cut is a fairly  
> major event. Our customers won't be too pleased if their $80 million  
> project has to be restarted from scratch because the stuff melted! So in  
> the event of a power cut, a big truck comes along and dumps a huge lump  
> of pig iron labelled "CAT POWER" outside our building, with a  
> ridiculously huge cable and a comically over-sized plug on the end.  
> (Seriously, the cable is thicker than some tree trunks!)

And what happens if the firm can't get you a CAT out in time? If it's that  
crucial shouldn't you at least have a CAT UPS or equivalent to tide you  
over.

-- 
Phil Cook

--
I once tried to be apathetic, but I just couldn't be bothered
http://flipc.blogspot.com

Post a reply to this message

Invisible <voi### [at] devnull> wrote:
> Stephen wrote:
> > Invisible <voi### [at] devnull> wrote:
> >> I'd say 3 AWG - but either way, it's less than 1 cm thick.
> >>
> >> Like I said, when they hook up the external generator, it comes with a
> >> cable well over 10 cm thick (!)
> >
> > A lot of that thickness will be insulation, shielding and armor.
>
> Probably.

Not probably but defiantly.

> The plug is physically larger than my head. The whole contraption looks
> like a giant's plaything has fallen out of the sky or something...

Yip and the reverse is true. In the old days, people who worked on high power
equipment thought that electronic connectors looked like toy stuff.

Stephen

Post a reply to this message

Phil Cook wrote:
> And lo on Fri, 09 Nov 2007 11:44:37 -0000, Invisible <voi### [at] devnull> did 
> spake, saying:
> 
>> Since we store stuff that has to be kept frozen, a power cut is a 
>> fairly major event. Our customers won't be too pleased if their $80 
>> million project has to be restarted from scratch because the stuff 
>> melted! So in the event of a power cut, a big truck comes along and 
>> dumps a huge lump of pig iron labelled "CAT POWER" outside our 
>> building, with a ridiculously huge cable and a comically over-sized 
>> plug on the end. (Seriously, the cable is thicker than some tree trunks!)
> 
> And what happens if the firm can't get you a CAT out in time? If it's 
> that crucial shouldn't you at least have a CAT UPS or equivalent to tide 
> you over.

The thing is:

1. The guys at CAT have a contractual obligation to arrive within X 
minutes of being called. If they fail to do this, they must pay us 
absurd amounts of money.

2. The freezers don't instantly heat up when the power is turned off. 
They have this thing called... thermal insulation. ;-) Not to mention 
the specific melting heat of water. (Do you have any idea how much ice 
there is in a -80°C freezer?)

Post a reply to this message

And lo on Fri, 09 Nov 2007 15:02:40 -0000, Invisible <voi### [at] devnull> did  
spake, saying:

> Phil Cook wrote:
>> And lo on Fri, 09 Nov 2007 11:44:37 -0000, Invisible <voi### [at] devnull>  
>> did spake, saying:
>>
>>> Since we store stuff that has to be kept frozen, a power cut is a  
>>> fairly major event. Our customers won't be too pleased if their $80  
>>> million project has to be restarted from scratch because the stuff  
>>> melted! So in the event of a power cut, a big truck comes along and  
>>> dumps a huge lump of pig iron labelled "CAT POWER" outside our  
>>> building, with a ridiculously huge cable and a comically over-sized  
>>> plug on the end. (Seriously, the cable is thicker than some tree  
>>> trunks!)
>>  And what happens if the firm can't get you a CAT out in time? If it's  
>> that crucial shouldn't you at least have a CAT UPS or equivalent to  
>> tide you over.
>
> The thing is:
>
> 1. The guys at CAT have a contractual obligation to arrive within X  
> minutes of being called. If they fail to do this, they must pay us  
> absurd amounts of money.

Yeah, but that's little compensation if as a result businesses stop using  
you and you fold

> 2. The freezers don't instantly heat up when the power is turned off.  
> They have this thing called... thermal insulation. ;-) Not to mention  
> the specific melting heat of water. (Do you have any idea how much ice  
> there is in a -80°C freezer?)

I'm just wondering as to the overall cost of a CAT UPS over the cost of  
the contract to bring in a CAT generator, which would also run all your  
electrical equipment.

-- 
Phil Cook

--
I once tried to be apathetic, but I just couldn't be bothered
http://flipc.blogspot.com

Post a reply to this message

Phil Cook wrote:
> And lo on Fri, 09 Nov 2007 15:02:40 -0000, Invisible <voi### [at] devnull> did 
> spake, saying:
> 
>> The thing is:
>>
>> 1. The guys at CAT have a contractual obligation to arrive within X 
>> minutes of being called. If they fail to do this, they must pay us 
>> absurd amounts of money.
> 
> Yeah, but that's little compensation if as a result businesses stop 
> using you and you fold

I don't think you understand what I mean by "absurd amounts of money". ;-)

[As in, like, if companies *did* stop using us, we'd *still* have so 
much money it wouldn't even matter...]

>> 2. The freezers don't instantly heat up when the power is turned off. 
>> They have this thing called... thermal insulation. ;-) Not to mention 
>> the specific melting heat of water. (Do you have any idea how much ice 
>> there is in a -80°C freezer?)
> 
> I'm just wondering as to the overall cost of a CAT UPS over the cost of 
> the contract to bring in a CAT generator, which would also run all your 
> electrical equipment.

Well, I'm sure somebody will have looked at that and decided it's not 
worth it. (I would think that for more than 3 seconds of cover, you'd 
need a battery larger than our entire office...)

Post a reply to this message

And lo on Fri, 09 Nov 2007 16:08:36 -0000, Invisible <voi### [at] devnull> did  
spake, saying:

> Phil Cook wrote:
>> And lo on Fri, 09 Nov 2007 15:02:40 -0000, Invisible <voi### [at] devnull>  
>> did spake, saying:
>>
>>> The thing is:
>>>
>>> 1. The guys at CAT have a contractual obligation to arrive within X  
>>> minutes of being called. If they fail to do this, they must pay us  
>>> absurd amounts of money.
>>  Yeah, but that's little compensation if as a result businesses stop  
>> using you and you fold
>
> I don't think you understand what I mean by "absurd amounts of money".  
> ;-)
>
> [As in, like, if companies *did* stop using us, we'd *still* have so  
> much money it wouldn't even matter...]

Sounds like you need a power cut, a narrow road, a tree, and a chainsaw.

>>> 2. The freezers don't instantly heat up when the power is turned off.  
>>> They have this thing called... thermal insulation. ;-) Not to mention  
>>> the specific melting heat of water. (Do you have any idea how much ice  
>>> there is in a -80°C freezer?)
>>  I'm just wondering as to the overall cost of a CAT UPS over the cost  
>> of the contract to bring in a CAT generator, which would also run all  
>> your electrical equipment.
>
> Well, I'm sure somebody will have looked at that and decided it's not  
> worth it. (I would think that for more than 3 seconds of cover, you'd  
> need a battery larger than our entire office...)

You'd think.

-- 
Phil Cook

--
I once tried to be apathetic, but I just couldn't be bothered
http://flipc.blogspot.com

Post a reply to this message

Invisible wrote:
> A0 paper.
> 
> As in, the largest standardised paper size that exists, at more than a
> meter wide. (2.5 feet by 4 feet, roughly.)
> 

To be precise, A0 has exactly 1m² area, while the longer side is
(shorter_side)*SQRT(2).

-- 
Eero "Aero" Ahonen
   http://www.zbxt.net
      aer### [at] removethiszbxtnetinvalid

Post a reply to this message

Invisible wrote:
> scott wrote:
>>> (Woah - 63A? o_O Anybody know what thickness of copper it takes to
>>> handle that kind of currentl? That's gotta be more like a girder than
>>> a wire!)
>>
>> Roughly double your standard 13A cable would do...  Look at the cable
>> going to the starter motor on your car, that's usually 100A or so.
> 
> 1. A car runs on 12V electrics, not 250V. Does that make a difference?

No.

> 2. Is maximum load proportional to diameter or cross section area? (The
> latter is quadratically propertional to diameter.)

Cross section area.
(But I don't know how it is with really large
cross sections and currents.)

-- 
Tor Olav
http://subcube.com

Post a reply to this message

Invisible nous apporta ses lumieres en ce 2007/11/09 07:36:
> scott wrote:
>>> (Woah - 63A? o_O Anybody know what thickness of copper it takes to 
>>> handle that kind of currentl? That's gotta be more like a girder than 
>>> a wire!)
>>
>> Roughly double your standard 13A cable would do...  Look at the cable 
>> going to the starter motor on your car, that's usually 100A or so.
> 
> 1. A car runs on 12V electrics, not 250V. Does that make a difference?
To my knowlege, only on the insulation.
The diameter of a cable is dictated the number of amps, it's insulation by the 
volts.
> 
> 2. Is maximum load proportional to diameter or cross section area? (The 
> latter is quadratically propertional to diameter.)
Would be the cross section. But you have proportionatly less surface area to 
evacuate any generated heat.
> 
>> Can't you print it out tiled, ie 8 A3 sheets (or however many it is) 
>> then just put them together?
> 
> Well, in principle yes. In practice, I very much doubt you'd ever get 
> the pieces to line up properly. (Ever notice how map books *always* put 
> the place you want to look at in the crease?) Plus I'm having enough 
> trouble finding somewhere to put an A3 printout without it getting 
> crinkled up... :-S
> 
> Apparently the planners have access to an A0 printer. I don't even want 
> to imagine what that must cost... ;-)
The price is irrelevent when the equipment allows you to do your job. Also, 
often, the highest priced options turns out to be the cheapest... in the long run.
Many mechanics can tell you: "I can't afford to buy any but the best tools 
available, whatever the price!"
This is also true for engineiring firms.

-- 
Alain
-------------------------------------------------
You know you've been raytracing too long when you invented glasses that can be 
configured to use variable resolution (eg. 320x240, 640x480, etc.), with POV-Ray 
style switches for other effects (eg. anti-aliasing, radiosity, etc.)
Vimal N. Lad / Gautam N. Lad

Post a reply to this message

Alain wrote:

> The price is irrelevent when the equipment allows you to do your job. 
> Also, often, the highest priced options turns out to be the cheapest... 
> in the long run.

I wish somebody could explain this to the idiots I work for...

Post a reply to this message

> (Woah - 63A? o_O Anybody know what thickness of copper it takes to handle 
> that kind of currentl? That's gotta be more like a girder than a wire!)

If it's less than 100 feet maybe #8? (~3 mm)

> 1. A car runs on 12V electrics, not 250V. Does that make a difference?

Yes, lots. Voltage is the size of the elephant, amperage is how fast he's
going when he runs you over. I think many cars will pull more than 100 A
cold starting though.
100 A * 12 V = 1200 W (~1.6 hp)
100 A * 220 V = 22 KW (~29.5 hp)

> 2. Is maximum load proportional to diameter or cross section area? (The 
> latter is quadratically propertional to diameter.)

It's proportional to the surface area. Thus all the stranded and braided 
wire.

Post a reply to this message

Tim Attwood wrote:

>> 2. Is maximum load proportional to diameter or cross section area? (The 
>> latter is quadratically propertional to diameter.)
> 
> It's proportional to the surface area. Thus all the stranded and braided 
> wire. 

Interesting. I thought braided wire was just so it bends without 
fracturing...

Post a reply to this message

Orchid XP v7 nous apporta ses lumieres en ce 2007/11/10 04:11:
> Alain wrote:
> 
>> The price is irrelevent when the equipment allows you to do your job. 
>> Also, often, the highest priced options turns out to be the 
>> cheapest... in the long run.
> 
> I wish somebody could explain this to the idiots I work for...
You need to show them the operational cost the the lowest priced option compared 
to that of the highest priced option. You also need to compare the quality of 
the final product, and the amount of rejects with what those rejects cost.

-- 
Alain
-------------------------------------------------
You know you've been raytracing too long when you keep a blacklist of people who 
ask questions about 3DFX products.
Alex McLeod a.k.a. Giant Robot Messiah

Post a reply to this message

Orchid XP v7 nous apporta ses lumieres en ce 2007/11/10 12:52:
> Tim Attwood wrote:
> 
>>> 2. Is maximum load proportional to diameter or cross section area? 
>>> (The latter is quadratically propertional to diameter.)
>>
>> It's proportional to the surface area. Thus all the stranded and 
>> braided wire. 
> 
> Interesting. I thought braided wire was just so it bends without 
> fracturing...
A solid wire have a smaler cross section than a braided or stranded wire of the 
same caliber, but will be stiffer. In a braided wire, there are gaps between the 
strands, and those make the cable whider.
So, yes, braided wires are needed when you need a supple wire, like that from a 
socket to some device. But, a solid wire is beter in a wall, where it don't need 
to change it's path once in place.

-- 
Alain
-------------------------------------------------
You know you've been raytracing too long when you hate games, but you buy Riven 
just to look at the pictures.
AmaltheaJ5

Post a reply to this message

Alain wrote:
> Orchid XP v7 nous apporta ses lumieres en ce 2007/11/10 12:52:
>> Tim Attwood wrote:
>>
>>>> 2. Is maximum load proportional to diameter or cross section area? 
>>>> (The latter is quadratically propertional to diameter.)
>>>
>>> It's proportional to the surface area. Thus all the stranded and 
>>> braided wire. 
>>
>> Interesting. I thought braided wire was just so it bends without 
>> fracturing...
> A solid wire have a smaler cross section than a braided or stranded wire 
> of the same caliber, but will be stiffer. In a braided wire, there are 
> gaps between the strands, and those make the cable whider.
> So, yes, braided wires are needed when you need a supple wire, like that 
> from a socket to some device. But, a solid wire is beter in a wall, 
> where it don't need to change it's path once in place.
> 
Adding to that, a braided wire might break, but there are enough cross 
connections that under most circumstances you won't notice it. 
Exceptions may be when connected to an amplifier. When I was young (or 
at least younger) we had a, probably cheap, coax cable that connected a 
guitar to an amplifier. If you shook it, you could here the 'water 
sloshing' over the amp. Funny, but not very useful. Another occasion
was when connecting a bush of electrodes to a self made ecg amplifier, 
those wires were long and shielded. Stepping on them would cause 
something that superficially looks like a (part of) a ecg complex, about 
the right amplitude and width. Very annoying if you are looking for 
complexes with a different than standard morphology and have to press 
the record button if you see one and the machine can not be used for a 
minute after you did record that artefact.

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Tim Attwood wrote:
...
>> 2. Is maximum load proportional to diameter or cross section area? (The 
>> latter is quadratically propertional to diameter.)
> 
> It's proportional to the surface area. Thus all the stranded and braided 
> wire. 

No, this is not true for DC currents and AC currents at low frequencies.

(Maybe your are thinking about the "skin effect" that appears at high
frequencies ?)

Here's some relevant links:

http://www.ibiblio.org/obp/electricCircuits/DC/DC_12.html#xtocid183892
http://www.epanorama.net/documents/wiring/wire_resistance.html
http://www.interfacebus.com/Copper_Wire_AWG_SIze.html

-- 
Tor Olav
http://subcube.com

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Tor Olav Kristensen wrote:
> Tim Attwood wrote:
> ...
>>> 2. Is maximum load proportional to diameter or cross section area? (The 
>>> latter is quadratically propertional to diameter.)
>> It's proportional to the surface area. Thus all the stranded and braided 
>> wire. 
> 
> No, this is not true for DC currents and AC currents at low frequencies.
> 
> (Maybe your are thinking about the "skin effect" that appears at high
> frequencies ?)

Well, it seems there are two relevant phenomina here.

1. Heat production, which is proportional to current and inversely 
proportional to cross-section area.

2. Heat dissapation, which is proportional to surface area.

I'm not sure which one is dominant...

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"Orchid XP v7" <voi### [at] devnull> a écrit dans le message de news: 
4736c72d$1@news.povray.org...
> 2. Heat dissapation, which is proportional to surface area.
>
Heat dissipation is propotionnal to surface area only if this area is free 
of insulation.

Marc

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Tim Attwood wrote:
>> 1. A car runs on 12V electrics, not 250V. Does that make a difference?
> 
> Yes, lots. Voltage is the size of the elephant, amperage is how fast he's
> going when he runs you over. I think many cars will pull more than 100 A
> cold starting though.

No, not for the sizing of the cable. If the cable has resistance of
0,01ohms and the current is 100 A, the cable will heat up with
100^2*0,01=100 W (P=I^2*R) and hold up 100*0,01=1 volt (U=I*R) of
voltage (this 1V is called the voltage loss of the cable). Rest of the
voltage (11V or 249V) will get to the final device and it'll have matter
there.

Practically everyone/-thing (lets say house heating, 10kW) needs power
(P, measured in watts). While P=U*I, we can produce 10kW of heat eg.
with either 1A*10kV, 10A*1kV, 100A*100V, 1kA*10V or 10kA*1V. If the
transmission lines to the house adds up with 1ohm, we'll heat the
transmission lines up with anything from 1W (1A^2*1ohm) to 100 000 000 W
= 100MW (10kA^2*1ohm). This is why the main transmission lines do not
have 230-400V voltage, but ~10-400kV voltages instead - to minimize the
power loss, which only heats up the outside air.

> 100 A * 12 V = 1200 W (~1.6 hp)
> 100 A * 220 V = 22 KW (~29.5 hp)

True, at the final device.

-- 
Eero "Aero" Ahonen
   http://www.zbxt.net
      aer### [at] removethiszbxtnetinvalid

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Invisible wrote:
> I used to own an old HP line plotter. (Do they still make those?) 

Every time I see my wife writing chinese by hand, it reminds me of fond 
hours watching the HP line plotter label stuff on the output page.


-- 
   Darren New / San Diego, CA, USA (PST)
     Remember the good old days, when we
     used to complain about cryptography
     being export-restricted?

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Tor Olav Kristensen wrote:
>> 2. Is maximum load proportional to diameter or cross section area? (The
>> latter is quadratically propertional to diameter.)
> 
> Cross section area.

Also depends on AC vs DC.

-- 
   Darren New / San Diego, CA, USA (PST)
     Remember the good old days, when we
     used to complain about cryptography
     being export-restricted?

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>> Roughly double your standard 13A cable would do...  Look at the cable 
>> going to the starter motor on your car, that's usually 100A or so.
>
> 1. A car runs on 12V electrics, not 250V. Does that make a difference?

No, the wire has to be the right thickness for the *current*, voltage 
doesn't make any difference to its current carrying capability.  That's why 
the power grid is at a stupidly high voltage, so that current is lower (for 
the same power) and hence the cables can be thinner and less power wasted by 
heat.

> 2. Is maximum load proportional to diameter or cross section area? (The 
> latter is quadratically propertional to diameter.)

Cross-sectional area.  IIRC the definition of resistance is something like 
material_resistivity*length/x-sec_area.  If the resistance of a cable is too 
high, then it will get too hot and melt.  Heat dissipated is I^2*R...

> Apparently the planners have access to an A0 printer. I don't even want to 
> imagine what that must cost... ;-)

Not *that* much, they just print on a roll of paper and work like an 
inkjet - just a bit wider :-)

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>>> Like I said, when they hook up the external generator, it comes with a
>>> cable well over 10 cm thick (!)
>>
>> A lot of that thickness will be insulation, shielding and armor.
>
> Probably.

It will probably be 3-phase as well if you are running large bits of lab 
equipment...

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>> Yeah, but that's little compensation if as a result businesses stop using 
>> you and you fold
>
> I don't think you understand what I mean by "absurd amounts of money". ;-)
>
> [As in, like, if companies *did* stop using us, we'd *still* have so much 
> money it wouldn't even matter...]

But what are you going to do with all the money if nobody uses you anymore 
because of your reputation of shoddy back-up plans?  How long will that 
money last paying everyones salaries? ;-)

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scott wrote:
>>> Yeah, but that's little compensation if as a result businesses stop 
>>> using you and you fold
>>
>> I don't think you understand what I mean by "absurd amounts of money". 
>> ;-)
>>
>> [As in, like, if companies *did* stop using us, we'd *still* have so 
>> much money it wouldn't even matter...]
> 
> But what are you going to do with all the money if nobody uses you 
> anymore because of your reputation of shoddy back-up plans?  How long 
> will that money last paying everyones salaries? ;-)

Well, it's not really my field, but presumably the people responsible 
for this stuff have looked into it quite thoroughly. ;-)

FWIW, we had a freezer fault over the weekend... Interesting coincidence.

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Phil Cook wrote:
> And lo on Fri, 09 Nov 2007 16:08:36 -0000, Invisible <voi### [at] devnull> did 
> spake, saying:
> 
>> Well, I'm sure somebody will have looked at that and decided it's not 
>> worth it. (I would think that for more than 3 seconds of cover, you'd 
>> need a battery larger than our entire office...)
> 
> You'd think.

Well, 6 mass spectrometers using 450 V electrics... That's gotta eat 
juice like candy. If you just wanted to power the freezers, that's 
probably quite reasonably - the compressor doesn't even have a 100% duty 
cycle, and it's only a small electric motor after all.

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>> But what are you going to do with all the money if nobody uses you 
>> anymore because of your reputation of shoddy back-up plans?  How long 
>> will that money last paying everyones salaries? ;-)
>
> Well, it's not really my field, but presumably the people responsible for 
> this stuff have looked into it quite thoroughly. ;-)

Yeh you'd hope so.  Presumably if the penalty amount is high enough, CAT 
would hire a helicopter or something to get you the generator on time (if it 
came to that) :-)

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scott wrote:
>>>> Like I said, when they hook up the external generator, it comes with a
>>>> cable well over 10 cm thick (!)
>>>
>>> A lot of that thickness will be insulation, shielding and armor.
>>
>> Probably.
> 
> It will probably be 3-phase as well if you are running large bits of lab 
> equipment...
> 

Never ceases to amaze me how thick 3-phase power cables appear, yet cut 
one open, and the wires encased in the cable aren't *that* thick, but 
there's a ton of "wadding" around the actual wires inside the cable. 
Extra fun when attempting to unplug a 3-phase device for the first time. 
I had no idea it had to twist-on.

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> Never ceases to amaze me how thick 3-phase power cables appear, yet cut 
> one open, and the wires encased in the cable aren't *that* thick, but 
> there's a ton of "wadding" around the actual wires inside the cable. Extra 
> fun when attempting to unplug a 3-phase device for the first time. I had 
> no idea it had to twist-on.

Yeh, we had this oven that was 3-phase, but only something like 23A. 
However, like you say, the cable was about 10x wider than a normal 13A mains 
cable, so cross-section 100x bigger.  I didn't see inside the cable, but I 
guess it was mostly shielding, armour and insulation...

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Darren New wrote:
> Tor Olav Kristensen wrote:
>>> 2. Is maximum load proportional to diameter or cross section area? (The
>>> latter is quadratically propertional to diameter.)
>>
>> Cross section area.
> 
> Also depends on AC vs DC.

At 50 Hz, does it matter?

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scott nous apporta ses lumieres en ce 2007/11/12 09:18:
>> Never ceases to amaze me how thick 3-phase power cables appear, yet 
>> cut one open, and the wires encased in the cable aren't *that* thick, 
>> but there's a ton of "wadding" around the actual wires inside the 
>> cable. Extra fun when attempting to unplug a 3-phase device for the 
>> first time. I had no idea it had to twist-on.
> 
> Yeh, we had this oven that was 3-phase, but only something like 23A. 
> However, like you say, the cable was about 10x wider than a normal 13A 
> mains cable, so cross-section 100x bigger.  I didn't see inside the 
> cable, but I guess it was mostly shielding, armour and insulation...
> 
> 
Each individual live whire is isulated, then there is a metal mesh protection, 
then an outer protective layer. Then, there is a ground (not isolated) and 
possibly a neutral whire. The neutral is also isolated and protected by a metal 
mesh. The whole thing is paded with ropes, encassed in an additional isolating 
layer, then 1 to 5 metal mesh armouring, plus, possibly a metal sheet shelding, 
all wrapt in an outer PVC or polypropylen outer shell.
It all adds up.

-- 
Alain
-------------------------------------------------
When the bosses talk about improving productivity, they are never talking about 
themselves.

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Eero Ahonen nous apporta ses lumieres en ce 2007/11/11 16:44:
> Tim Attwood wrote:
>>> 1. A car runs on 12V electrics, not 250V. Does that make a difference?
>> Yes, lots. Voltage is the size of the elephant, amperage is how fast he's
>> going when he runs you over. I think many cars will pull more than 100 A
>> cold starting though.
> 
> No, not for the sizing of the cable. If the cable has resistance of
> 0,01ohms and the current is 100 A, the cable will heat up with
> 100^2*0,01=100 W (P=I^2*R) and hold up 100*0,01=1 volt (U=I*R) of
> voltage (this 1V is called the voltage loss of the cable). Rest of the
> voltage (11V or 249V) will get to the final device and it'll have matter
> there.
> 
> Practically everyone/-thing (lets say house heating, 10kW) needs power
> (P, measured in watts). While P=U*I, we can produce 10kW of heat eg.
> with either 1A*10kV, 10A*1kV, 100A*100V, 1kA*10V or 10kA*1V. If the
> transmission lines to the house adds up with 1ohm, we'll heat the
> transmission lines up with anything from 1W (1A^2*1ohm) to 100 000 000 W
> = 100MW (10kA^2*1ohm). This is why the main transmission lines do not
> have 230-400V voltage, but ~10-400kV voltages instead - to minimize the
> power loss, which only heats up the outside air.
> 
>> 100 A * 12 V = 1200 W (~1.6 hp)
>> 100 A * 220 V = 22 KW (~29.5 hp)
> 
> True, at the final device.
> 
We have 750KV AC and 1000KV DC transmition lines all over the place. Hydroquebec 
pioneered the 750KV lines with Churchill Falls and the Manic complex. It's 
pioneering 1000000 DC transmition with the Bay James. Why do you think that they 
invested several $1000000's a year for over 20 years on that technology?

-- 
Alain
-------------------------------------------------
You can go anywhere you want if you look serious and carry a clipboard.

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Alain wrote:
> We have 750KV AC and 1000KV DC transmition lines all over the place.

Damn, you people are way front of me and my knowledge.

> Hydroquebec pioneered the 750KV lines with Churchill Falls and the Manic
> complex. It's pioneering 1000000 DC transmition with the Bay James. Why
> do you think that they invested several $1000000's a year for over 20
> years on that technology?

DC transmission? Possibly because DC is more tolerant to ripples, if it
gets hacked back to AC after all.

-- 
Eero "Aero" Ahonen
   http://www.zbxt.net
      aer### [at] removethiszbxtnetinvalid

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Eero Ahonen nous apporta ses lumieres en ce 2007/11/13 12:41:
> Alain wrote:
>> We have 750KV AC and 1000KV DC transmition lines all over the place.
> 
> Damn, you people are way front of me and my knowledge.
> 
>> Hydroquebec pioneered the 750KV lines with Churchill Falls and the Manic
>> complex. It's pioneering 1000000 DC transmition with the Bay James. Why
>> do you think that they invested several $1000000's a year for over 20
>> years on that technology?
> 
> DC transmission? Possibly because DC is more tolerant to ripples, if it
> gets hacked back to AC after all.
> 
No! 750KV AC is an average value, it have a crest value of about 1000KV, whitch 
is about the maximum you can reliably handle without having sheet arcs between 
transmission whires. As DC never goes down to zero, you transmit 100% of the 
time, not about 75% as in the case of AC.
Multi mega-wats lines over 400 to more than 800 miles long. You realy need to 
reduce that current...
Another advantage: you need 1 less whire for the transmission. AC lines normaly 
have 3 whires, while DC lines only use 2.
Yes! it get's transformed back to AC at the converter stations, and reduced down 
to 750KV.

I do know somebody that works at IREQ. (Institut de Recherches Électriques du 
Québec)

-- 
Alain
-------------------------------------------------
WARNING: The consumption of alcohol may make you think you can logically 
converse with members of the opposite sex without spitting.

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> Multi mega-wats lines over 400 to more than 800 miles long. You realy need 
> to reduce that current...
> Another advantage: you need 1 less whire for the transmission. AC lines 
> normaly have 3 whires, while DC lines only use 2.
> Yes! it get's transformed back to AC at the converter stations, and 
> reduced down to 750KV.

It would be interesting to know how they do the DC-->AC conversion with that 
much power.

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Alain wrote:
> No! 750KV AC is an average value, it have a crest value of about 1000KV,
> whitch is about the maximum you can reliably handle without having sheet
> arcs between transmission whires. As DC never goes down to zero, you
> transmit 100% of the time, not about 75% as in the case of AC.

Aaaa. I misread ("750kV AC", I read "750kV DC"), but still I probably
wouldn't have tought the right answer.

> Multi mega-wats lines over 400 to more than 800 miles long. You realy
> need to reduce that current...

True that. 750kV vs. 1Mv has remarkable difference.

> Another advantage: you need 1 less whire for the transmission. AC lines
> normaly have 3 whires, while DC lines only use 2.

OTOH, with 3 wires you can transfer 3 phases of AC - for one phase 2 is
enough (possibly even 1+ground is possible).

> Yes! it get's transformed back to AC at the converter stations, and
> reduced down to 750KV.

Yep. And there goes all the glitches that have been inducted to the DC
voltage, so at the end there's cleaner AC (nearer to sin).

-- 
Eero "Aero" Ahonen
   http://www.zbxt.net
      aer### [at] removethiszbxtnetinvalid

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