mozart
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How Much Power In PC Ports On Board Planes?

Sat May 26, 2007 2:03 pm

I was on a Swiss flight (Airbus A340-300) from NRT to ZRH the other day and I tried to user the laptop power installed in my seat.

What happened was that my computer actually did receive some power, but just for 5 or so seconds. After that, power cut. The purser explained to me that this was probably due to the fact that my laptop power adapter used too much power. He looked at my adapter and said "aah, 1.7A, that is too much".

I am no electrical engineer so I don't even know whether looking at the Ampere is the right thing to do (maybe the fact that the adapter also said "90W" would have been more revealing).

Still, I have the question: is there a maximum power that in-seat PC ports on planes can deliver? How much? If there are differences, do they depend upon the aircraft model or the airline?

Thanks!
 
rwessel
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RE: How Much Power In PC Ports On Board Planes?

Sat May 26, 2007 6:04 pm

The two ratings are related, but in a complex way. For a simple resistive load (like an incandescent light bulb) volts times amps (VA) equals watts. Computer power supplies behave far differently. Most common are switching type supplies, which take current only during part of the power cycle (they effectively switch on and off frequently, hence the name), leading to divergent watt and VA ratings. The watt rating remains the amount of power the device can actually consume over time, but it "takes" that power in short bursts at the higher VA level.

The power source has to manage both loads - the instantaneous VA load, and the continuous watt load*.

We usually assign a "power factor" to such devices, which lets us simply relate the two numbers. Small PC-type switching power supplies usually get a power factor rating in the .55 to .7 range, which means that your nominal 90W laptop power supply might need between 128 and 163VA from the power source. Some inexpensive power supplies do considerably worse (your 90W/1.7A adapter works out to a worst cast PF of .48 - assuming 110VAC, again).

Now the ISPSS ports on aircraft have surprisingly poorly standardization. In practice, high voltage ports that can supply 93, 75 and 51 watts (at 110VAC) to the adapter exist (there are also low voltage 12V, 15V and 28V ports, just to confuse things - if you had to borrow an adapter from the airline, you probably had one of those). Note that these are often labeled 90, 70 and 50W. The design inverse power factor is even less well specified, but seems to be in the ballpark of 2.0 for the systems I've seen spec'd. So your laptap's power supply is right on the edge of what the highest power ports usually available can supply. And if you were plugging into a 75W/1.4A/110VAC port, you were basically doomed to start with. And if you're using one of the cheap adapters, you can be adding significant losses to the connection.

And all of these systems are heavily self protected, so they will shut you down if you try to overload them.

You may want to check your airline's website for information. LH spec 70W 110VAC ISPSS, for example.

You may also want to look into whether or not a better (more efficient/lower draw) power supply is available for your laptop. On some laptops you have a choice of a 65 or 90W power brick - the former being better for aircraft use, but it charges your laptop rather more slowly. Or get a smaller laptop.  

And isn't that a a long winded way of saying that if the system shut you off when you plugged into it, you were drawing too much power?



*If you're ever buying a UPS for a computer, be sure to take both VA and watt ratings into account. UPS are invariably sold on their VA ratings (IOW, the "Model 1000" UPS can supply 1000VA). The cheaper UPS often skimp on their equivalent wattage with power factors as low as .5. The UPS that can supply 1000VA and 500W is obviously much less of a UPS than the one that can supply 1000VA and (a much more reasonable) 760W.

[Edited 2007-05-26 11:13:25]
 
David L
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RE: How Much Power In PC Ports On Board Planes?

Sat May 26, 2007 6:49 pm

Quoting Rwessel (Reply 1):
And isn't that a a long winded way of saying that if the system shut you off when you plugged into it, you were drawing too much power?

Well, yes, but very useful nevertheless. It filled a lot of blanks in my understanding of the subject.  Smile
 
Meerkat
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RE: How Much Power In PC Ports On Board Planes?

Tue May 29, 2007 2:37 pm

A trick that was taught to me by a CX FA (their system is also 70W, and at the time my laptop was rated at 90), is to take out the battery. Then it worked fine. She told me that sometimes the system can provide enough juice to either recharge the battery or power the laptop, but not both at the same time.
Anyway, as I said, it worked a treat.
 
flexo
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RE: How Much Power In PC Ports On Board Planes?

Tue May 29, 2007 6:28 pm

Quoting Rwessel (Reply 1):

That was a very interesting read and stirred up a question I had for a while: What are the pros and cons concerning the different voltages in different countries (230VAC vs. 110VAC)?
Would it be easier for an aircraft to supply either one of those and would the required wire diameters differ?

I understand that the supplied power has to be the same VA in either system but it seems that the higher Ampere levels in 110VAC systems could cause greater challenges design wise than in 230VAC systems.
 
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Starlionblue
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RE: How Much Power In PC Ports On Board Planes?

Tue May 29, 2007 8:54 pm

Quoting Mozart (Thread starter):
What happened was that my computer actually did receive some power, but just for 5 or so seconds. After that, power cut. The purser explained to me that this was probably due to the fact that my laptop power adapter used too much power. He looked at my adapter and said "aah, 1.7A, that is too much".

What kind of laptop do you have? 17 inch monitor? Many laptops will notice they don't have enough power for operation AND charging and only allow one at a time in these situations. Otherwise you can take the battery out. However some laptops are so dumb they won't turn on then despite external power.

Quoting Mozart (Thread starter):

I am no electrical engineer so I don't even know whether looking at the Ampere is the right thing to do (maybe the fact that the adapter also said "90W" would have been more revealing).

A x V = W. Note that we are talking DC power for Empower and car style plugs.

Quoting Flexo (Reply 4):
I understand that the supplied power has to be the same VA in either system but it seems that the higher Ampere levels in 110VAC systems could cause greater challenges design wise than in 230VAC systems.

It is rare to find AC 120 or 240 on an aircraft. Most have DC, with either 15 volts (Empower system) or 14.7 volts (car socket).



Two things weird me out here:
1. As has been mentioned in the thread, some sockets can't provide enough power for certain modern laptops. A 17 inch laptop will draw a lot more than an old 14 inch. The whole industry is going from 72w to 90w PSUs. Couldn't the airlines see this coming? It was hardly a secret. The whole thing smacks of short term thinking.
2. Apart from the larger screens, today's average laptops (and desktops) actually draw less power in normal use than their equivalents a few years ago. This is due to a low power/heat revolution in processors (Video and Central). Compare my 2 year old P4 at 76w with my new Core 2 Duo at 57w. So what's the deal with the 72w->90w switch? Probably the screens. But most people don't have a 17 inch laptop.
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Analog
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RE: How Much Power In PC Ports On Board Planes?

Tue May 29, 2007 10:04 pm

Quoting Starlionblue (Reply 5):
But most people don't have a 17 inch laptop.

Certainly not open in coach.  crowded 

Quoting Starlionblue (Reply 5):
It is rare to find AC 120 or 240 on an aircraft. Most have DC, with either 15 volts (Empower system) or 14.7 volts (car socket).

110V AC sockets are not that rare; though it'd be nice to see more of them. 3 of my last 4 flights (CO & KE) had 110V AC power (accepted US flat & European round plugs). UA has them on its P.S. flights.

As an electrical engineer, I'd say that 15V DC is better than 110V AC for in-seat power in many ways except one: people need special adapters. For that reason alone the 110V AC sockets will probably (hopefully?) dominate.

Note the the AC sockets actually are at 110V, not 115V or 120V. http://www.astronicsaes.com/products/ac-in-seat.asp
 
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Starlionblue
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RE: How Much Power In PC Ports On Board Planes?

Wed May 30, 2007 1:16 am

Quoting Analog (Reply 6):

110V AC sockets are not that rare; though it'd be nice to see more of them. 3 of my last 4 flights (CO & KE) had 110V AC power (accepted US flat & European round plugs). UA has them on its P.S. flights.

You're right. I am probably just used to AABig grin

Quoting Analog (Reply 6):
As an electrical engineer, I'd say that 15V DC is better than 110V AC for in-seat power in many ways except one: people need special adapters. For that reason alone the 110V AC sockets will probably (hopefully?) dominate.

I agree, somewhat. But then again a universal AC/DC adapter (Empower, carstyle plug, 110-240) is only a little larger than the "just AC" one and only 50-60 bucks. Not much if you're going to travel a lot, besides which many companies let you expense it.

Quoting Analog (Reply 6):
Note the the AC sockets actually are at 110V, not 115V or 120V.

I did not know that thanks.
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rwessel
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RE: How Much Power In PC Ports On Board Planes?

Wed May 30, 2007 12:28 pm

Quoting Flexo (Reply 4):
That was a very interesting read and stirred up a question I had for a while: What are the pros and cons concerning the different voltages in different countries (230VAC vs. 110VAC)?

The thickness of insulation you need is roughly proportional to the voltage, and the size of the wires you need is roughly proportional to the current. So you can move the same amount of power over a half sized wire when you double to voltage. The insulator size is usually less of an issue, since the insulator on end use type wiring is usually much bigger than is electrically required because it needs to be mechanically rugged enough.

The selection of 110V in the US goes back to Edison's use of 110V DC. When Westinghouse/Tesla's AC eventually proved a superior solution, they wanted to go 240V, but the regulators wouldn't allow anything higher than 110V into homes. Eventually they decided that doubling the voltage *was* a good idea for larger devices, so most houses in the US are wired to a center-tapped 220/240VAC system, where half the outlets in the house are on one side (netting 110-120V), and half on the other side, and the 220V outlets (like the one by your air conditioner or electric stove) using both halves.

The reason for the center tapped system had to do with compatibility and ease of conversion from the old 110VAC only system. In the early 110VAC days, when power-consumption-per-house was much lower, the block was supplied with a connection to a center tapped 220VAC transformer. One side of the block ended up on one side of the transformer, and the other side of the block on the other side of the transformer. This allowed the power companies to basically build half as many cheaper transformers (a transformer with a center tapped 220VAC output is a bit more costly than a straight 220VAC output, but a fair bit cheaper than a 110VAC output). When 220VAC started being run into individual homes, it didn’t require an infrastructure change to just connect a house to both halves, despite that being a decidedly sub-optimal solution in some cases. Most notably there’s always a fair bit of imbalance in the current draws on the two halves of the system.

The Europeans just started with Tesla's advice and implemented 240V/60Hz.

I doubt anyone would go the 110VAC route today, and you might actually go for a somewhat higher voltage than 240V. Something in the vicinity of 440V three phase has a lot of appeal.

OTOH, DC distribution would be a very compelling option today, since most of the stuff that doomed it in the first place now has solutions. Most notably, transformers made it easy to step AC voltages up and down, and there was no simple way to do that with DC. That required low voltage DC to be run all the way from the power plant to the end user. This required the generating stations to be located very close to the end users or else the wire sizes and/or losses would have been prohibitive (there are darn good reasons that long haul lines are all 110KV+). These days DC-to-DC voltage conversion is relatively easy. AC works relatively well for simple resistive loads like incandescent lights and heaters (for which DC works just as well), and works pretty well for electric motors (and DC motors are certainly available), but almost everything else starts by converting the AC back to DC. High voltage DC distribution would avoid a lot of conversions, not to mention simplifying shipping power around the network (by definition you eliminate the phase requirements).
 
Analog
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RE: How Much Power In PC Ports On Board Planes?

Wed May 30, 2007 12:40 pm

Quoting Rwessel (Reply 8):

The selection of 110V in the US goes back to Edison's use of 110V DC. When Westinghouse/Tesla's AC eventually proved a superior solution, they wanted to go 240V, but the regulators wouldn't allow anything higher than 110V into homes.

Then the regulators messed up, since "110V AC" goes above 150V. 110V refers to the RMS (root mean square) average of the voltage.  Smile

Quoting Rwessel (Reply 8):
These days DC-to-DC voltage conversion is relatively easy.

But AC-AC conversion is easier, especially at tens of thousands of volts and thousands of amps. Right? (This is not my field of expertise).
 
rwessel
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RE: How Much Power In PC Ports On Board Planes?

Wed May 30, 2007 2:12 pm

Quoting Analog (Reply 9):
Then the regulators messed up, since "110V AC" goes above 150V. 110V refers to the RMS (root mean square) average of the voltage.

Indeed.  Wink

Quoting Analog (Reply 9):
But AC-AC conversion is easier, especially at tens of thousands of volts and thousands of amps. Right? (This is not my field of expertise).

Yes, AC-to-AC conversion is easier: obviously you only need a hunk of iron (and sometimes not even that) and a few thousand turns of wire, and no active components at all.

Semiconductor DC voltage converters basically convert to AC and then back to DC with something transformer-like in the middle, although that can be more capacitative than inductive, and the conversion often is not to a sine wave (square waves being trivial and efficient to generate). This still has size efficiencies since the "magnetics" (or equivalent) in the middle are invariably run at multiple kilohertz, and are *tiny* compared to the normal 50/60Hz magnetics in a transformer. The converters are often single integrated circuits, and while each can handle a limited load, the inputs and outputs being DC makes it trivial to just parallel as many of these as you need. And at extremely high voltages, you can run bunches in series too - DC makes that sort of thing *so* easy.

The biggest bipolar (two wire) systems currently run at 3GW and 500KV, and while the electronics at the ends of those are far from trivial, they’re not particularly complex or expensive (at least from the perspective of anything that can handle those kinds of numbers). Monopole systems up to 1.5GW have been built too.

Other schemes exist as well, motor generator sets (basically a DC motor connected with a shaft to a DC generator) being an old one still getting a fair bit of use, along with many varieties of more traditional inverter-transformer-inverter designs (again, often taking advantage of much higher frequencies).

But, DC-to-DC conversion is now simple end efficient *enough* that DC distribution would be practical. Not least because you can suddenly reduce the number of conductors from three for traditional AC to two or even one (for monopole/earth return systems), and you can significantly increase the amount of power transmitted over a given amount of copper, while significantly reducing your transmission losses (not least, there are no inductive or capacitative losses with DC transmission). Those savings can pay for the more complex switching gear.

A fair number of HVDC transmission lines exist. These have been used to connect between unsynchronized networks, for long haul lines (especially *very* long distance lines to remote locations where the 2-4%/1000km losses on AC lines are painful), and in situations where it's difficult to add conductors to meet an increasing load (for example undersea cables). The current rule-of-thumb is that HVDC is cost effective for undersea lines longer than about 50km, and overhead lines longer than about 750km, based only on the cable costs vs. the electronics costs.

In general, this is limited to major grid interconnections, since few end users "want" DC at the moment. A noteworthy amount of electronic gear is available with DC power supplies, and the increased efficiency makes that somewhat popular in large computer rooms (not only for reduced power requirements, but for the corresponding reduction in cooling requirements, and simpler more reliable standby power systems), but almost all of those run large rectifiers outside the computer room, and the power mains are still traditional AC.


And a correction: I mentioned Europe used 60Hz in my prior post, this is, of course, incorrect, most of Europe uses 50Hz.
 
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Starlionblue
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RE: How Much Power In PC Ports On Board Planes?

Wed May 30, 2007 10:28 pm

Wow Rwessel. Thanks for the posts. You have a nice way of explaining technical detail while keeping it simple and interesting enough for people like me to understand.
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jacobin777
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RE: How Much Power In PC Ports On Board Planes?

Thu May 31, 2007 12:32 am

Quoting Meerkat (Reply 3):
A trick that was taught to me by a CX FA (their system is also 70W, and at the time my laptop was rated at 90), is to take out the battery. Then it worked fine. She told me that sometimes the system can provide enough juice to either recharge the battery or power the laptop, but not both at the same time.
Anyway, as I said, it worked a treat.

....another way is to charge the battery for a while and then turn on the laptop...this method works for me..... yes 
"Up the Irons!"
 
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Starlionblue
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RE: How Much Power In PC Ports On Board Planes?

Thu May 31, 2007 12:43 am

Quoting Jacobin777 (Reply 12):
.another way is to charge the battery for a while and then turn on the laptop...this method works for me...

Depends on the laptop. Yours seems to charge the battery less aggressively at when it is more "full". But it's not the only variant.
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Analog
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RE: How Much Power In PC Ports On Board Planes?

Thu May 31, 2007 1:15 am

Here's a related web site that I discovered through Google. Looks interesting, though I can't vouch for it's accuracy.
http://users.pandora.be/worldstandards/electricity.htm

Quoting Rwessel (Reply 8):

I doubt anyone would go the 110VAC route today, and you might actually go for a somewhat higher voltage than 240V. Something in the vicinity of 440V three phase has a lot of appeal.

Higher voltage AC is more lethal, though. The question is by how much. I imagine that other factors like plug design and GFI requirements are probably more important in this regard.

Quoting Rwessel (Reply 10):
you can significantly increase the amount of power transmitted over a given amount of copper, while significantly reducing your transmission losses (not least, there are no inductive or capacitative losses with DC transmission).

I've always thought it would be cool, if you lived under a high voltage power lines, to make a large coil and hold it near the line to steal power.

Quoting Rwessel (Reply 10):

And a correction: I mentioned Europe used 60Hz in my prior post, this is, of course, incorrect, most of Europe uses 50Hz.

From the article I liked to above, it seems that that 50Hz was chosen because "the number 60 didn't fit the metric standard unit sequence (1,2,5)", therefore Europe chose a significantly less efficient frequency (bigger x-formers, etc.). 60Hz is better than 50Hz for many of the same reasons that aircraft use 400Hz AC power. Of course 60Hz is much easier to hear: the 120Hz 2nd harmonic. Listen to a big transformer.

Rwessel: I'd also like to add my thanks for the posts..
 
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Starlionblue
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RE: How Much Power In PC Ports On Board Planes?

Thu May 31, 2007 1:24 am

Quoting Analog (Reply 14):

Higher voltage AC is more lethal, though.

Not that I'm an expert, but as I understand it amperage controls lethality. A jolt of static electricity from a Van de Graaf generator can be tens of thousands of volts. But since the amperage is minimal, you don't die. And if you increase voltage, you decrease amperage for the same wattage output.

But as I said, I'm not an expert.
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Analog
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RE: How Much Power In PC Ports On Board Planes?

Thu May 31, 2007 3:06 am

Quoting Starlionblue (Reply 15):

Not that I'm an expert, but as I understand it amperage controls lethality.

And voltage controls amperage... The relationship may be highly non-linear when dealing with the human body (not like V = IR), but the correlation is there, especially for low impedance sources (like wall outlets).

Quoting Starlionblue (Reply 15):
And if you increase voltage, you decrease amperage for the same wattage output.

Nothing says the power is the same for a zap... the potential power output of a wall socket is many times more than what it would take to kill someone.

That being said, I'm not an expert on this either.
 
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Starlionblue
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RE: How Much Power In PC Ports On Board Planes?

Thu May 31, 2007 3:30 am

Quoting Analog (Reply 16):

Nothing says the power is the same for a zap... the potential power output of a wall socket is many times more than what it would take to kill someone.

Jepp. So I guess if we go from 110 to 400 it's a moot point anyway. Big grin
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rwessel
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RE: How Much Power In PC Ports On Board Planes?

Thu May 31, 2007 8:23 am

Quoting Starlionblue (Reply 15):
Not that I'm an expert, but as I understand it amperage controls lethality.

That's basically correct. Something around 100ma your heart will go into fibrillation and you'll die unless someone can restore it back to a normal rhythm. You'll be unable to breathe if you're getting more than about 75ma, and will probably be unable to let go of a wire if you're flowing more than about 10ma.

Oddly, getting more than about 200ma actually improves your chances for survival since that's strong enough that your heart clamps down completely, but does not go into fibrillation. So if you're removed from the circuit soon enough, and you've avoided serious tissue damage from electrical burns, your heart will typically just start beating again.

Obviously if you grab onto something that can source a (practically) unlimited amount of current (like your average power outlet), a higher voltage will more-or-less increase the current flow proportionately.

Higher voltages have some additional hazards too. For example, dry skin is normally pretty high resistance (which is a major reason why accidentally grabbing a 110 plug is typically not harmful). A high voltage can actually arc through your skin and connect to the much more conductive wet and salty stuff underneath (which will significantly increase current flow - assuming that's available from the source).

And someone mentioned plug design. Yes, getting rid of the *horrible* US NEMA 5-15 style plug/receptacle would be an outstanding idea. There are any number of designs available where you can never have an exposed pin that's live.
 
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Starlionblue
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RE: How Much Power In PC Ports On Board Planes?

Thu May 31, 2007 9:11 am

Quoting Rwessel (Reply 18):

And someone mentioned plug design. Yes, getting rid of the *horrible* US NEMA 5-15 style plug/receptacle would be an outstanding idea. There are any number of designs available where you can never have an exposed pin that's live.

Interesting. Can you give an example?

BTW for truly horrid design I give you the UK plug. ENORMOUS. Not to mention all the fuses EVERYWHERE except the fuse box. And those switches. But I digress.
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rwessel
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RE: How Much Power In PC Ports On Board Planes?

Thu May 31, 2007 10:15 am

Quoting Starlionblue (Reply 19):
Interesting. Can you give an example?

Sure, almost any plug in use in Europe. The German CEE 7/4 (aka Schuko), for example:

http://en.wikipedia.org/wiki/Schuko

Or for two wire/limited current applications, the CEE 7/16 Europlug:

http://en.wikipedia.org/wiki/Europlug

Those fit into the CEE 7/4 and French "Type E" receptacles as well. Note how the pins are insulated on the top parts - by the time the pin is far enough into the receptacle to make contact, only the insulated portion remains exposed.

The higher current (and grounded) 7/4s or 7/7s have a recessed design where not only does the plug fill the entire socket before the mains pins make contact, the ground is also connected before the mains pins are.

In both cases there is no time when a live pin is exposed, you can't even have a sheet of paper slide down between the plug and receptacle and touch live pins (as you can with the NEMA 5-15s).

Another good feature is a built in mechanism to prevent anything but a properly designed plug from getting connected to a power line. This can be a system of shutters (on the British BS 1363 the ground pin, which is longer, moves a lever which moves the shutters over the power pins), or it can be a switch built into the socket that internally disconnects the power if the right shape socket is not inserted. Both of those (plus the tight fitting socket) reduce the risk of spills getting to the conductors as well.

Quoting Starlionblue (Reply 19):
BTW for truly horrid design I give you the UK plug. ENORMOUS. Not to mention all the fuses EVERYWHERE except the fuse box. And those switches. But I digress.

An oddity of the British system is that they allow quite high currents to be run to the outlets (higher than the typical power cord can handle, in fact), thus requiring fuses in the BS 1363 plugs. This makes a certain amount of sense in that you can match the fuse to the device in question, but I don't think it's a great idea over all. High current outlets are not needed often enough that it's a big problem to have a special outlet/plug.

But while a smaller plug is nice, it's not a worthwhile tradeoff for the exposed live connectors on the NEMA 5-15s. Even the bulky (current) BS 1163s would be an improvement.

The NEMA 5-15s are "horrible," because they're flatly unsafe.
 
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Starlionblue
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RE: How Much Power In PC Ports On Board Planes?

Thu May 31, 2007 10:26 am

Quoting Rwessel (Reply 20):
hose fit into the CEE 7/4 and French "Type E" receptacles as well. Note how the pins are insulated on the top parts - by the time the pin is far enough into the receptacle to make contact, only the insulated portion remains exposed.

Oh I see what you mean. Hadn't thought of that. While I think it would be hard to replace the US plug (too big an install base), would it not be possible to at least insulate the top part of the plug? Also, if the sockets were remade so that current only flowed when the pins were all the way in, could the plug be retained?

Quoting Rwessel (Reply 20):

Another good feature is a built in mechanism to prevent anything but a properly designed plug from getting connected to a power line. This can be a system of shutters (on the British BS 1363 the ground pin, which is longer, moves a lever which moves the shutters over the power pins), or it can be a switch built into the socket that internally disconnects the power if the right shape socket is not inserted. Both of those (plus the tight fitting socket) reduce the risk of spills getting to the conductors as well.

This also has child safety advantages. You've now made me nervous. My girls are 2 and 20 months old. We call the older one "little mechanic" since she tinkers with everything. Time to superglue the plugs to the sockets...

Quoting Rwessel (Reply 20):

But while a smaller plug is nice, it's not a worthwhile tradeoff for the exposed live connectors on the NEMA 5-15s. Even the bulky (current) BS 1163s would be an improvement.

The NEMA 5-15s are "horrible," because they're flatly unsafe.

Good point.

Quoting Rwessel (Reply 20):
An oddity of the British system is that they allow quite high currents to be run to the outlets (higher than the typical power cord can handle, in fact), thus requiring fuses in the BS 1363 plugs. This makes a certain amount of sense in that you can match the fuse to the device in question, but I don't think it's a great idea over all.

Agreed. Fuses belong in the fuse box unless we're talking GFCI. Also the whole "fuse in the plug" thing somewhat ignores the home tinkerer who replaces plugs and so forth, probably without matching the correct strength fuse.
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Jetlagged
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RE: How Much Power In PC Ports On Board Planes?

Thu May 31, 2007 11:11 am

Quoting Starlionblue (Reply 21):
Agreed. Fuses belong in the fuse box unless we're talking GFCI. Also the whole "fuse in the plug" thing somewhat ignores the home tinkerer who replaces plugs and so forth, probably without matching the correct strength fuse.

The fuse is there to protect the power cord and house wiring from the appliance, not the other way around. The typical UK "ring main" power wiring means you might only have two power circuits in a house, one per floor. All a fusebox can do is limit the total current on each circuit. Fuses in plugs gives more flexibility and better protection. The wrong size fuse is better than no fuse at all.

Home tinkering with wiring is now illegal under our latest "nanny state" laws. All electrical work has to be done or at least approved by a qualified electrician. It may still be legal to change a fuse.  Wink I also remember the "good old days" when nothing was sold with plugs fitted. Now that was asking for trouble! Unthinkable now.

Returning to the question of in flight PC power, my Sony Vaio has a power supply the size of a house brick.  weightlifter  I was flying coach on BA once and managed to blag a free laptop adaptor from the F/A. However with the laptop drawing so much current it was useless. It didn't occur to me to try removing the battery!
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BreninTW
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RE: How Much Power In PC Ports On Board Planes?

Thu May 31, 2007 12:03 pm

The reason why laptop power supplies have "grown" to up to 90 W from earlier generations is simply because of the additional number of power-sapping devices built into modern laptops.

The first laptop I worked on (10 years ago) had a screen, FDD, HDD, a tiny amount of slow RAM and processor (maybe a few other small things thrown in). It's power requirements were limited to those devices. The CPU was a relatively slow processor that didn't give off much heat, didn't require fancy cooling and didn't draw much power.

My current laptop (a year old) has a high-brightness 15.4" LCD that chews power, Bluetooth, WLAN, USB 2.0, a DVD writer, dual-core processor (which requires additional fans/cooling), IEEE1394, masses of DDR2 RAM, and a high-speed, high-capacity HDD ... all of which draw power (and lots of it).

Modern laptops have so many more components that are designed to be FAST -- not particularly energy-efficient (although this is changing). Modern laptop processors and GPUs are indeed more energy-efficient than (say) five years ago, but they still draw more power than they did (five years ago) -- simply because they're so much faster.

Another reason why power supplies are so much "larger" today is to satisfy the demand for fast charging of batteries. At my company, we offer 65 W and 90 W power supplies for some of our laptops -- the 90 W supplies allow the battery to be charged in less than two hours (typically), while the 65 W power supplies require over three hours to fully charge most batteries [these numbers assume the laptop is not being used -- they're much higher if the laptop is being used, between 3 h (90 W) and 4 h (65 W)].

Quoting Starlionblue (Reply 5):
So what's the deal with the 72w->90w switch?
 
rwessel
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RE: How Much Power In PC Ports On Board Planes?

Thu May 31, 2007 12:25 pm

Quoting Starlionblue (Reply 21):
Oh I see what you mean. Hadn't thought of that. While I think it would be hard to replace the US plug (too big an install base), would it not be possible to at least insulate the top part of the plug? Also, if the sockets were remade so that current only flowed when the pins were all the way in, could the plug be retained?

The installed base makes this a problem, but a standardized plug design (perhaps a big circle like the European 7/4) with a recessed plug might be the best compromise. You might be able to insulate a couple of mm of the pin too, but any more than that, and they won't make proper contact with old style outlets anymore. A new plug in a new outlet would then be fairly safe. You could still plug an old plug into a new outlet since the opening for the recessed socket would be fairly large (obviously a really big "plug" like a wall-wart power supply would be incompatible) - this would help since the gap between the plug and the wall would be somewhat hidden in the recess. And a new plug would fit into old outlets, and would also help some because at least some of the pin would be insulated.

Then add some sort of automatic shutter. You couldn't do the (excellent) British BS 1363 style where the shutters are actuated by the longer ground pin, since not everything has a ground pin (non-grounded BS 1363 devices have a dummy "ground" pin just to actuate the shutter). But something like the double shutter child safety outlet would be doable (see below). Alternatively an active interruption type design would not be that hard to do, although more expensive.

Quoting Starlionblue (Reply 21):
This also has child safety advantages. You've now made me nervous. My girls are 2 and 20 months old. We call the older one "little mechanic" since she tinkers with everything. Time to superglue the plugs to the sockets...

I like the child proof outlets which have shutters over the two power pin sockets. The two shutters are rigged so that you cannot push just one open, but if you push on both simultaneously (like when you're inserting a plug with both pins intact) they both open. These are cheap too - under $10 at your local hardware store.
 
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Starlionblue
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RE: How Much Power In PC Ports On Board Planes?

Thu May 31, 2007 1:00 pm

Quoting Rwessel (Reply 24):
I like the child proof outlets which have shutters over the two power pin sockets. The two shutters are rigged so that you cannot push just one open, but if you push on both simultaneously (like when you're inserting a plug with both pins intact) they both open. These are cheap too - under $10 at your local hardware store.

I'll look at those. Now we just use the semisoft plastic ones. If I'm not strong enough to get it out with my bare hands she certainly isn't for a while yet.

Quoting Jetlagged (Reply 22):
Home tinkering with wiring is now illegal under our latest "nanny state" laws. All electrical work has to be done or at least approved by a qualified electrician. It may still be legal to change a fuse.

Heh. Well just because it's illegal doesn't mean nobody does it. I feel much safer in the US or Sweden where each circuit (more than two  Wink )has a proper fuse in the fuse box. Joe Sixpack is much less likely to tinker with the fusebox.

Quoting Jetlagged (Reply 22):
Returning to the question of in flight PC power, my Sony Vaio has a power supply the size of a house brick. weightlifter I was flying coach on BA once and managed to blag a free laptop adaptor from the F/A.

My recommendation is to get a third party power supply to replace the brick. they are often smaller.

Quoting Brenintw (Reply 23):
Modern laptop processors and GPUs are indeed more energy-efficient than (say) five years ago, but they still draw more power than they did (five years ago) --

True. However this is only at peak load. Modern CPUs and GPUs are better at shutting down parts on the fly when they are not needed.

Only partly relevant since we're talking desktop processors, but my 2 year old Pentium 4 (630) drew 78w at peak load. My new Core 2 Duo, which is 3-5 times faster, draws 57w at peak load. 2-3 years ago, laptops were already on low power processors. As you say, the peripherals matter. A lot. My new X60, with a 12.1 inch screen, has a friggin 7-9 hour battery life. Compare with a T60p with a 15 inch screen on the same capacity battery and you get 4-5 hours.
"There are no stupid questions, but there are a lot of inquisitive idiots."
 
Analog
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RE: How Much Power In PC Ports On Board Planes?

Fri Jun 01, 2007 1:47 am

Quoting Rwessel (Reply 20):
Even the bulky (current) BS 1163s would be an improvement.



Quoting Jetlagged (Reply 22):

Home tinkering with wiring is now illegal under our latest "nanny state" laws. All electrical work has to be done or at least approved by a qualified electrician. It may still be legal to change a fuse.

Gotta love the UK's electric code, talk about nanny state. No real power outlets in bathrooms. $#$!
 
DrDeke
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RE: How Much Power In PC Ports On Board Planes?

Fri Jun 01, 2007 4:57 am

Quoting Rwessel (Reply 8):
The Europeans just started with Tesla's advice and implemented 240V/60Hz.



Quoting Rwessel (Reply 10):
And a correction: I mentioned Europe used 60Hz in my prior post, this is, of course, incorrect, most of Europe uses 50Hz.

Interestingly enough, I have heard a rumor that Tesla was in favor of 60Hz systems (with 240V/60Hz being his preferred) due to the smaller size of transformers/etc required at the higher frequency. There are at least a few countries that use the 240V/60Hz system, one of which is Peru, which I found when I visited there.



Quoting Analog (Reply 14):
I've always thought it would be cool, if you lived under a high voltage power lines, to make a large coil and hold it near the line to steal power.

I've heard of this done on farms and such properties. My understanding is that you need a very large coil with many turns to make it worthwhile, and that it happens enough that power companies look for it and bust people they catch doing it. It also seems like installing such a coil might be a bit dangerous. You'd have to be careful, anyway, since there'd be no way to "turn it off".



Quoting Rwessel (Reply 20):
The NEMA 5-15s are "horrible," because they're flatly unsafe.

Agreed. I've had several situations where I've been trying to plug in some device with a 5-15 plug into a socket in some difficult to reach location and either felt lucky afterwards that I didn't slip my finger onto a prong and get shocked, or in some cases, I've actually decided I'd better stop and move things out of the way in order to reduce the risk.



DrDeke
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Analog
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RE: How Much Power In PC Ports On Board Planes?

Fri Jun 01, 2007 8:15 am

Quoting DrDeke (Reply 27):

Interestingly enough, I have heard a rumor that Tesla was in favor of 60Hz systems (with 240V/60Hz being his preferred) due to the smaller size of transformers/etc required at the higher frequency. There are at least a few countries that use the 240V/60Hz system, one of which is Peru, which I found when I visited there.

South Korea uses 220V/60Hz, if I recall correctly.

Your rumor is confirmed here:

Quoting Analog (Reply 14):
Here's a related web site that I discovered through Google. Looks interesting, though I can't vouch for it's accuracy.
http://users.pandora.be/worldstandards/electricity.htm
 
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Jetlagged
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RE: How Much Power In PC Ports On Board Planes?

Fri Jun 01, 2007 8:26 am

Quoting Analog (Reply 26):
Gotta love the UK's electric code, talk about nanny state. No real power outlets in bathrooms.

That is a sensible one. What else will stop stupid people using hairdryers, other electrical stuff near baths.
The glass isn't half empty, or half full, it's twice as big as it needs to be.
 
Analog
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RE: How Much Power In PC Ports On Board Planes?

Fri Jun 01, 2007 8:42 am

Quoting Jetlagged (Reply 29):

That is a sensible one. What else will stop stupid people using hairdryers, other electrical stuff near baths.

Never heard of GFIs, have they? Plus they do allow 1 outlet for razors (1 amp I think). Of course that's more than enough to kill. What do you use if there is no outlet? An extension cord.

Same with outdoor outlets; not allowed. Stupid UK laws. (2nd hand info; I may be wrong). It's very frustrating looking for an outdoor outlet, in the dark, on a house that has no outdoor outlets.  banghead 

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