Electrical specifications for on-board auxilary power

thenorthern · 26 Feb 2015

On some trains you are probably aware that they have auxiliary power sockets for passengers at seats which are normally marked with a sign saying "For Laptops and Mobile Phone chargers only".

From using the sockets for my mobile phone I generally find that the amount of current is less than a standard BS 1363 (Standard United Kingdom) as my phone takes longer to charge probably hence the Laptops and Mobile Phone chargers only rule.

It made me think though what is the specifications for the on-board power, I can't think it would be too much different from the standard consumer power although I think the amount of amps will be less but the voltage will be the same.

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WatcherZero · 26 Feb 2015

I would imagine similar to shaver sockets, 40 watts or so?

AM9 · 26 Feb 2015

thenorthern said:
On some trains you are probably aware that they have auxiliary power sockets for passengers at seats which are normally marked with a sign saying "For Laptops and Mobile Phone chargers only".

From using the sockets for my mobile phone I generally find that the amount of current is less than a standard BS 1363 (Standard United Kingdom) as my phone takes longer to charge probably hence the Laptops and Mobile Phone chargers only rule.

It made me think though what is the specifications for the on-board power, I can't think it would be too much different from the standard consumer power although I think the amount of amps will be less but the voltage will be the same.

Not sure what you are trying to say but laptop power supplies and mobile phone chargers are designed to work on ac voltages between 110v and 240v and at frequencies between 48 and 60Hz. A laptop supply would draw up to about 100W over that voltage range. so the amenity supply is probably rated at 0.5 to 1 A at a nominal 230v 50Hz. A tablet charger would draw a maximum of 0.1A and a phone charger about half that, so the current available would not make any difference to the time to charge.
BS1363 is a specification for plugs and sockets of the type with rectangular pin contacts. Meeting that is as easy as fitting the sockets to the coaches. It has nothing to do with the maximum current available from the sockets (subject to a maximum limit of 13A) which as I have explained above in unlikely to more than 1A per outlet.
Of much more importance would be the quality of the ac waveform. As it would come from an onboard inverter (probably static - i.e. electronic) the waveform may not be as pure a sinewave as normally present on a domestic supply. Even so, modern portable power adaptors would have no problem creating a charging supply equally from all ac sources.

Greybeard33 · 26 Feb 2015

If you use the phone while it is on charge, the battery takes longer to charge than if the phone is in standby, because more of the charger output is absorbed by the display backlight etc. I suspect this accounts for the impression that charging is slower on the train, rather than any difference in the power supply.

thenorthern · 26 Feb 2015

AM9 said:
Of much more importance would be the quality of the ac waveform. As it would come from an onboard inverter (probably static - i.e. electronic) the waveform may not be as pure a sinewave as normally present on a domestic supply. Even so, modern portable power adaptors would have no problem creating a charging supply equally from all ac sources.

That may be the case, I generally find Pendos are more "Constant" with power output than Voyagers which may be down to the way the train is powered but I don't know for sure.

AM9 · 26 Feb 2015

thenorthern said:
That may be the case, I generally find Pendos are more "Constant" with power output than Voyagers which may be down to the way the train is powered but I don't know for sure.

How are you measuring the constant quality of the power supply?

PaxVobiscum · 26 Feb 2015

I suspect we will find that he is not measuring at all.

brianthegiant · 26 Feb 2015

PaxVobiscum said:
I suspect we will find that he is not measuring at all.

I think we might be talking about % availability or interruptions per hour. which is crudely measurable with LED indicators on PSUs or devices. either way the spec is somewhat looser than for the public supply.

edwin_m · 26 Feb 2015

thenorthern said:
It made me think though what is the specifications for the on-board power, I can't think it would be too much different from the standard consumer power although I think the amount of amps will be less but the voltage will be the same.

If the device is trying to draw more amps than the socket can provide then it is most likely the overload protection circuits would cut off power to that socket. The only other possible way of reducing the current would be to reduce the voltage at the socket, but if a switch mode power supply is plugged in then presumably a reduced input voltage would cause it to draw more current to maintain the same output power.

So assuming a socket cuts out, it will probably restore after a short time, otherwise it would need resetting manually which is not something the train operator would want to spend time doing. I guess it's possible that if a charge drawing a bit more more current than the socket can comfortably provide that the socket would repeatedly switch off and on again, giving the impression it is charging more slowly.

AM9 · 26 Feb 2015

edwin_m said:
If the device is trying to draw more amps than the socket can provide then it is most likely the overload protection circuits would cut off power to that socket. The only other possible way of reducing the current would be to reduce the voltage at the socket, but if a switch mode power supply is plugged in then presumably a reduced input voltage would cause it to draw more current to maintain the same output power.

So assuming a socket cuts out, it will probably restore after a short time, otherwise it would need resetting manually which is not something the train operator would want to spend time doing. I guess it's possible that if a charge drawing a bit more more current than the socket can comfortably provide that the socket would repeatedly switch off and on again, giving the impression it is charging more slowly.

The OP is talking about a mobile phone charger, which would draw less than 0.1A from a degraded 230v supply. Even a 10W supply as would be provided for an ipad would draw less than 0.15A. The power must come from the train's 'hotel' supply so its actual voltage would be independant of the traction load and the OHLE voltage. It would essentially be a constant voltage supply, maybe not quite up to UK domestic specifications.
As you say, the individual socket may have been subject to intermittent operation, but that would be a fault rather than due to a mere mobile phone charger, especially if the socket was rated up to laptop demands.
I doubt whether this would be the case for all or even most Voyagers when all or most Pendolinos don't have any problems.

Nym · 26 Feb 2015

thenorthern said:
On some trains you are probably aware that they have auxiliary power sockets for passengers at seats which are normally marked with a sign saying "For Laptops and Mobile Phone chargers only".

First of all, thanks for refering to these correctly as sockets...

From using the sockets for my mobile phone I generally find that the amount of current is less than a standard BS 1363 (Standard United Kingdom) as my phone takes longer to charge probably hence the Laptops and Mobile Phone chargers only rule.

It made me think though what is the specifications for the on-board power, I can't think it would be too much different from the standard consumer power although I think the amount of amps will be less but the voltage will be the same.

The power for sockets provided to the public on trains is usually derived from a dedicated static convertor, usually one or two provided per car.
One such supplier is Martek, their convertor is shown below.
http://www.martekpower.com/products/en/asp.html
Many other brands are of course available, but for retro fitting to older trains, a different set of standards have to be met in relation to the supply.

New equipment only really needs to meet things like EN50155 and EN50121-3-2 and be installed to maintain EN50121-3-1.

Older stock ideally needs equipment that meets the old standards, BRB/LUL/RIA-12 and BRB/LUL/RIA-13, finding suppliers willing to support this is much more difficult.

As a PS, depending on the train, the supplies can be very different.

Control and emergency supplies tend to be DC, but the AC supplies can vary wildly in terms of frequency, phase count and voltage.

PaxVobiscum · 26 Feb 2015

Nym said:
First of all, thanks for refering to these correctly as sockets...

Hear, hear!

WatcherZero · 26 Feb 2015

What else would someone refer to them as? plug sockets? electrical outlets? Glory holes?

:P

Later would give you a shock if you 'plugged' in.

jon0844 · 27 Feb 2015

My phone can be charged at almost 2A so it seems like charging on a train would take ages.

dcsprior · 27 Feb 2015

jonmorris0844 said:
My phone can be charged at almost 2A so it seems like charging on a train would take ages.

Why? Others have said here that the sockets on trains wile likely provide 0.5 - 1 amps, at 230 volts; so at least 115 watts.

This is enough to power a charger which is 50% efficienct (any real modern power-supply will be far more efficient than this) which outputs 57.5 watts.

At 5 volts (USB voltage) that's 11.5 amps, almost six times what your phone can draw.

Bigfoot · 27 Feb 2015

Out put of my charger is 2amps at 5v. The input current at 100-240v is 0.35 amps. Never had an issue with on board supplies charging my stuff.

jon0844 · 27 Feb 2015

Misread the post! That's fine then. Even the new Qualcomm Quick Chargers would be okay too then.

cjmillsnun · 27 Feb 2015

Nym said:
First of all, thanks for refering to these correctly as sockets...

The correct UK sparky term is socket outlet.

AM9 · 27 Feb 2015

Bigfoot said:
Out put of my charger is 2amps at 5v. The input current at 100-240v is 0.35 amps. Never had an issue with on board supplies charging my stuff.

That's because 2A @ 5V = 10 Watts (of power)
0.35 A from 100V is 35 W
The current from a 230V supply would likely max out below 0.2 A

AnonymousUser1 · 27 Feb 2015

jonmorris0844 said:
My phone can be charged at almost 2A so it seems like charging on a train would take ages.

2A @ 5 v ...

Power = VA ...

your charger is drawing fractions of an Amp current at 230V to provide 2A at 5 v

Electrical specifications for on-board auxilary power

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