Subject:
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Re: Metroliner question
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Newsgroups:
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lugnet.trains
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Date:
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Sat, 23 Feb 2002 16:01:36 GMT
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Viewed:
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848 times
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In lugnet.trains, Scott Arthur writes:
> > AC power is more efficient and can travel longer
> > distances, therefore requiring less voltage. (or something like that.)
in part true. Mostly because of transformers rasing voltage/reducing amps for
same HP/wattage. (that's why long distance power cables are at 500 KV or even
750 KV, because it allows low amp power supply of massive amounts of power-the
amps loose energy to resistance, the voltage doesn't unless grounded)
> Despite that, AC power distribution is High Voltage/Low Current (was DC the
> same?) as this ensures low power losses (can’t remember the relationship).
E=RI (E=voltage, R=resistance (ohms), I= amps)
> Supply AC voltage is lowered (and current raised) at what we call
> "sub-stations" in the UK (big transformers?).
Hence, the effiency of AC. DC requries MG sets or static inverters to rase
voltage. There are practical limits to both of these, so effiency is affected.
AC transformers are really only limited by the breakdown voltage of the wire
insulation used internal to them.
Key to this is that power (exc
> losses) is the same for both supply & distribution: Power = Volts * Amps. In
> the UK, most supply points (exc hobs, showers etc ) are 13A / 240v. That
> gives us 3.1kw. I assume supplies with 110v have higher current?
Nope, most 110 outlets over here are 15 amp (1500 w max/1350 w cont) loading.
You can get 20 amp outlets, but they are less common. More common for high
powered applications is the use of split phase wiring with 220 V and up to 40
amps (dryer, range)
> What I keep meaning to understand is 3-phase AC... but not today!
Ah, so much fun. 3 Ph is interesting, and reduces the amount of wire required
to transmit the same amount of power.
James P
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Message is in Reply To:
 | | Re: Metroliner question
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| (...) High School Physics: To get the same efficiency from DC, we'd literally need a power station in every district of a city/town. Despite that, AC power distribution is High Voltage/Low Current (was DC the same?) as this ensures low power losses (...) (22 years ago, 22-Feb-02, to lugnet.trains)
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