From time to time I've wondered why the standard US lighting voltage
was (when I was a kid) 110 volts and not a "rounder" number like 100 or
I think I may have located a believable answer, purportedly in Edison's
own words, on page 66 of this document, under the heading "Why 110 Volts":
Now, can someone tell me when and why it was "increased" to 115 and then
120 volts? Will I live to see it become 125 volts in a few years? <G>
(Next, why did the early phonograph records revolve at 78 RPM? and have
you ever wondered why 33 and 45 add up to 78?)
"Earliest rotation speeds varied widely, but between 1900-1925 most records
were recorded between 74-82 rpm. In 1925, 78.26 rpm was chosen as the standard
because of the introduction of the electrically powered synchronous turntable
motor. This motor ran at 3600 rpm with a 46:1 gear ratio which produced 78.26
rpm. In parts of the world that used 50 Hz current, the standard was 77.92
Doug Miller (alphageek at milmac dot com)
higher voltage reduces current a little too.....
euope uses higher voltage to keep conductors smaller, and remember the
power to your home gets converted many times by transformers before
arriving at your socket. low voltage can cause big grief so the keep
raising it over ime
Plus I'd bet that the significantly higher capacitive currents between
conductors would waste a huge amount of power in resistive losses.
IIRC 400Hz power was used in aircraft circa WWII, I lost track of
whether it's still a standard there.
400hz is still used in aircraft. The computer industry used 400hz for
their big machines up until fairly recently when switching power
supplies and CMOS made it unnecessary.
We used to have big MG sets in computer rooms or a switching UPS that
provided the 400hz.
From what I can tell, most US systems are 60Hz since they can buy
standard equipment. Some older systems are strange for historical
reasons (generation equipment). I believe the NYC subway system is
25Hz, or some such. I'd be very surprised if any used 400Hz since
saving weight isn't as important as reducing losses.
If a transformer designed for 60 Hz is operated at 400 Hz, losses would
be less than at 60 Hz, although output voltage with a heavy load may droop
if not much work went into reducing leakage inductance. 400 Hz
transformers at 400 Hz also normally have less losses than 60 Hz ones of
same volt/amp ratings being operated at 60 Hz. And a 400 Hz transformer
would cost less to make than a 60 Hz one of the same ratings, since it
would be smaller and use fewer turns of wire.
The way I heard it, a lower frequency was preferred for motors and
that's why 60 Hz was chosen. Also, 400 Hz could be high enough for wire
inductance to be a problem with longer distance transmission lines, but I
don't know how badly or if transmission line inductance affected 60 Hz
being chosen for our main AC power frequency.
- Don Klipstein ( email@example.com)
It's not an issue of transformer losses, rather distribution
FOr the AUS distribution system? AFAIK, 60Hz was chosen because it
was a good tradeoff of several variables (transformer cost, losses,
generation ease, and likely a dozen other considerations). As far
as locomotion, I believe 60Hz is rather recent and used because the
equipment is off-the-shelf. Most older subway and commuter systems
are in the 25Hz range. I highly doubt modern DE engines are 60Hz.
I do believe it was one of the factors in the selection. Flicker
could be the reason that it went no lower too. Dunno.
Turns out the Apollo Lunar Module used 400 Hz power (that is, if
Wikipedia is to be believed):
And the Monterey Bay Aquarium Research Institute's underwater ROV
(Remotely Operated Vehicle) runs on 400 Hz:
Lots of others if you google for "propulsion system" "400 hz" (with the
Just as McDonald\'s is where you go when you\'re hungry but don\'t really
care about the quality of your food, Wikipedia is where you go when
Large aircraft ( like jetliners) are generally 400 Hz, 115/200 volts 3 phase
ac , some smaller ones have 28 volt dc systems.
The 400 Hz power is supplied on the ground either by engine driven
alternators or by converters, they used to be large motor/generator sets
but these have mostly been replaced by solid state converters, which are
smaller, lighter and more efficient especially at low loads, though not so
reliable as the old MG sets.
"David Nebenzahl" < firstname.lastname@example.org> wrote in message
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