| Topic: |
Science > Physics |
| User: |
"aasiyah" |
| Date: |
09 Feb 2005 05:29:02 AM |
| Object: |
how does voltage from a wall plug vary with time |
Hi
if you would sketch how the voltage from the wall plug varies with
thime, how would it look like, how can you find it out? I know it has
something to do with three phase since it is in AC signal. (a wall
plug in Europe with three-phase, 50 Hz and 230V)
Please help me
Thankyou
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| User: "CWatters" |
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| Title: Re: how does voltage from a wall plug vary with time |
09 Feb 2005 05:49:13 AM |
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"aasiyah" <alam_seher@hotmail-dot-com.no-spam.invalid> wrote in message
news:4209f3fe$1_1@127.0.0.1...
Hi
if you would sketch how the voltage from the wall plug varies with
thime,
http://www.silcom.com/~aludwig/images/snake.gif
how would it look like, how can you find it out? I know it has
something to do with three phase since it is in AC signal. (a wall
plug in Europe with three-phase, 50 Hz and 230V)
No. most wall sockets carry just a single phase. The exception being cooker
points and other high power in some countries. These do have all three
phases but it's still one phase on each electrical contact. It looks like
three seperate sine waves (compared to earth).
The best diagram I could find looks like this...
http://www.basilnetworks.com/article/hybrid/images/sinewave100.gif
but ignore the vertical axis label.
.
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| User: "aasiyah" |
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| Title: Re: re:how does voltage from a wall plug vary with time |
15 Feb 2005 11:36:57 AM |
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CWatterswrote:
"aasiyah" <alam_seher@hotmail-dot-com.no-spam.invalid> wrote in
message
news:420a3a8c$1_2@127.0.0.1...
so from this graph http://en.wikipedia.org/wiki/Three_phase you
would
say only one of these three voltages goes through a wall plug? How
does this work..
What do you mean how does this work?
All you need is one live (sine wave) and one neutral
("0V").[/quote:1e0309f5e6]
where does the neutral wave come from and why is it there, what's its
purpose.
Please correct me if im wrong; the voltage from a wall plug is only
with one wave- the sine wave- and NOT in three phase. Three phase is
rarely used. BUT why is not three phase used in ordinary wall plugs,
since it is not what is its purpose?
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| User: "John Popelish" |
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| Title: Re: how does voltage from a wall plug vary with time |
15 Feb 2005 12:09:01 PM |
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aasiyah wrote:
CWatterswrote:
What do you mean how does this work?
All you need is one live (sine wave) and one neutral
("0V").[/quote:1e0309f5e6]
where does the neutral wave come from and why is it there, what's its
purpose.
Please correct me if im wrong; the voltage from a wall plug is only
with one wave- the sine wave- and NOT in three phase. Three phase is
rarely used. BUT why is not three phase used in ordinary wall plugs,
since it is not what is its purpose?
In the U.S., the wall sockets have a 120 volt sine wave on the narrow
slot and zero volts on the wide slot. When you connect a load between
them, the sine voltage drives current back and forth through the load
and that current returns back to the source on the zero volt line.
The pole transformer produces 240 volts across its secondary winding,
but that winding has its center point grounded (imagine an electrical
analog of a see saw), so that one end goes positive when the other end
goes negative. Half of the receptacles in the house are connected
between the grounded center and one end, and the other half are
connected between the grounded center and the other end. Big loads
like ranges and cloths dryers and water heaters are connected across
the full winding and see the full 240 volts, instead of only half of
it.
But all this is a single phase system.
--
John Popelish
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| User: "Michael Moroney" |
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| Title: Re: how does voltage from a wall plug vary with time |
16 Feb 2005 10:37:50 AM |
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alam_seher@hotmail-dot-com.no-spam.invalid (aasiyah) writes:
All you need is one live (sine wave) and one neutral
("0V").[/quote:1e0309f5e6]
where does the neutral wave come from and why is it there, what's its
purpose.
It is a return or reference. Electric current flows in loops, think of
it like this: If electricity flows "out" from somewhere it must flow back
"in" somewhere.
Three transformers of three phase can be wired in two different ways:
In a triangle (called delta) or in the shape of the letter Y (called
wye or Y or star). In the wye connection, one end of the three
transformers are connected at a single point. This is a logical reference
point and it is almost always the neutral.
Please correct me if im wrong; the voltage from a wall plug is only
with one wave- the sine wave- and NOT in three phase. Three phase is
rarely used. BUT why is not three phase used in ordinary wall plugs,
since it is not what is its purpose?
You need three transformers (instead of one) and more wires. No real need
for smallish loads like a house.
Electric motors for single phase need special windings to start rotating
when switched on. Without them it'll just sit there and hum (and smoke
sometimes). Three phase power will automatically start three phase motors
rotating. Important for large motors, no need for windings that don't
contribute to the running of the motor. Also, if you plot the total power
used over the full cycle it'll be constant with three phase if the loads
on the three phases are all the same. Single phase starts at zero, goes
to a max, back to zero, to a max etc. Also important for large motors,
generators too, the power pulsations will translate into vibration, etc.
--
-Mike
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| User: "Nick Rouse" |
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| Title: Re: how does voltage from a wall plug vary with time |
16 Feb 2005 04:28:39 PM |
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alam_seher@hotmail-dot-com.no-spam.invalid (aasiyah) wrote in message news:<42123339$1_2@127.0.0.1>...
CWatterswrote:
"aasiyah" <alam_seher@hotmail-dot-com.no-spam.invalid> wrote in
message
news:420a3a8c$1_2@127.0.0.1...
so from this graph http://en.wikipedia.org/wiki/Three_phase you
would
say only one of these three voltages goes through a wall plug? How
does this work..
What do you mean how does this work?
All you need is one live (sine wave) and one neutral
("0V").[/quote:1e0309f5e6]
where does the neutral wave come from and why is it there, what's its
purpose.
Please correct me if im wrong; the voltage from a wall plug is only
with one wave- the sine wave- and NOT in three phase. Three phase is
rarely used. BUT why is not three phase used in ordinary wall plugs,
since it is not what is its purpose?
Three phase supplies are not used domestically because of the extra
cost yielding very little benefit for most domestic needs. It needs
three fuses or circuit breakers per circuit, a more complicated three
phase meter, at least three pole switches, at least 3 current carrying
conductors (4 with a balanced neutral) and with neutral and protective earth
5 pin plugs and sockets. A three phase supply is of no benefit to the user
for resistive loads (lighting and heating) and for electrical motors
up to about 1kW the slight gain is not worth the extra cost. For industrial
users there are gains to be made. Three phase motors are smaller, more
efficient, run more smoothly and have much greater starting torque than
single phase motors of the same rating. For multi-kilowatt motors these gains
are worth the cost of the supply installation. Network electricity is always
generated three phase and the generating companies do not like large
imbalances between the phases. Here in Britain and I suspect elsewhere
the generating companies charge industrial users according to the maximum
installed capacity as well as for the energy used. A single phase load
that drew three times the per phase current of a three phase load would
cost a lot more.
Three phase supplies in Europe are different to the normal American
system. The three phases are generated balanced about neutral (rather
than having one phase earthed). Power is transmitted and transformed
up and down in a balanced pattern. In places in or close to urban
centres (In England that is almost everywhere) the power is transformed
down to its final voltage 230 or 240V in large chunks (100kW or more)
and fed along the road as three phase. Domestic and light commercial users
are connected to one phase and neutral with each phase supplying each third
house. The pole transformers supplying just one house that are so common
in America are almost unknown here. Since the voltage is high there
is no need for two voltages and two styles of plugs and no possibility
of connecting two live conductors with different phases.
There are disadvantages of course, it is considerably more lethal.
Nick Rouse
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| User: "aasiyah" |
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| Title: Re: how does voltage from a wall plug vary with time |
11 Feb 2005 03:34:52 AM |
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CWatterswrote:
"aasiyah" <alam_seher@hotmail-dot-com.no-spam.invalid> wrote in
message
news:420b9bc2$3_2@127.0.0.1...
If you sketch it in AC, then it's a constant.
can you please elaborate, constant what?
let me try for him...
230V AV is always 230V AC. It only varies when there is noise, a power
cut
or similar transient - most of the time it's constant 230V
AC.[/quote:a116ac91bd]
So what you are saying is that it has nothing to do with 'three
phase'?
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| User: "aasiyah" |
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| Title: Re: how does voltage from a wall plug vary with time |
13 Feb 2005 03:35:07 AM |
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Nick Rousewrote:
Uncle Al <UncleAl0@hate.spam.net> wrote in message
news:<420A4E25.357F5B08@hate.spam.net>...
Although 50Hz lighting may flicker in absolute terms more than 60Hz
the
difference is not nearly as much as is perceived by those who have
lived
most of their lives in 60Hz areas when visiting 50Hz areas.
Experiments have
shown that long exposure to one frequency of flicker causes a
distinct
notch in the visual frequency response. In visiting America from
here
in Britain, I find the lighting somewhat more flickery that at home
but not as much as American friends visiting here who find it hard
to see how I put up with such lighting.
Transformers built for 50Hz are not less efficient than those built
for 60Hz.
but plug in a transformer built for 60Hz into a 50Hz supply and it
will heat
up more. If built to operate at the same maximum magnetic flux
levels
(by having proportionately greater core cross section or
proportionally more primary
turns or a bit of both) a 50Hz transformer would be more efficient
than
a 60Hz one although bigger.
Even higher frequencies give much smaller devices but not
necessarily
much cheaper as
steps have to be taken to keep the losses down. 400Hz aircraft
transformers tend to use very thin laminations of cobalt iron which
is
many times more expensive than silicon steel used at 50 & 60 Hz
The cleanliness of the sinewaves is very dependant on the nature of
the
load in your vicinity. A largely linear load will leave the
waveform
clean
but substantial non-linear loads such as discharge lighting,
rectifiers or
non-power factor corrected switched mode power supplies can distort
the
voltage waveform for other users substantially. 5% harmonic
distortion is quite
common close to sights where such loads make up a large fraction of
the
power used locally.
The original question asked about wall plugs (sockets) in Europe.
Anti-phase
live conductors are never found in domestic supplies (although
building
sites use portable transformers that transform 240 or 230V down to
an
earthed
centre tapped 110V). As stated in an earlier post three phase
supplies
are very rare here in domestic situations and in the few cases they
are used
they tend to be fixed wiring. I have not come across any three phase
sockets approved for use in Europe that you would want in your
house.
Nick Rouse
Why isnt three phase used, what is the 'danger'?
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| User: "aasiyah" |
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| Title: Re: how does voltage from a wall plug vary with time |
10 Feb 2005 11:37:06 AM |
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petewrote:
aasiyah wrote:
Hi
if you would sketch how the voltage from the wall plug varies with
thime, how would it look like, how can you find it out? I know it
has
something to do with three phase since it is in AC signal. (a wall
plug in Europe with three-phase, 50 Hz and 230V)
If you sketch it in AC, then it's a constant.
--
pete[/quote:08f66c4991]
can you please elaborate, constant what?
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| User: "CWatters" |
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| Title: Re: how does voltage from a wall plug vary with time |
10 Feb 2005 03:15:49 PM |
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"aasiyah" <alam_seher@hotmail-dot-com.no-spam.invalid> wrote in message
news:420b9bc2$3_2@127.0.0.1...
If you sketch it in AC, then it's a constant.
can you please elaborate, constant what?
let me try for him...
230V AV is always 230V AC. It only varies when there is noise, a power cut
or similar transient - most of the time it's constant 230V AC.
.
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| User: "Androcles Androcles@ MyPlace.org" |
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| Title: Re: how does voltage from a wall plug vary with time |
11 Feb 2005 02:53:30 AM |
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"aasiyah" <alam_seher@hotmail-dot-com.no-spam.invalid> wrote in message
news:420b9bc2$3_2@127.0.0.1...
petewrote:
aasiyah wrote:
Hi
if you would sketch how the voltage from the wall plug varies with
thime, how would it look like, how can you find it out? I know it
has
something to do with three phase since it is in AC signal. (a wall
plug in Europe with three-phase, 50 Hz and 230V)
If you sketch it in AC, then it's a constant.
--
pete[/quote:08f66c4991]
can you please elaborate, constant what?
Here's the sketch:
http://www.androc1es.pwp.blueyonder.co.uk/3phase.JPG
Androcles.
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| User: "Richard Herring" |
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| Title: Re: how does voltage from a wall plug vary with time |
09 Feb 2005 05:50:53 AM |
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In message <4209f3fe$1_1@127.0.0.1>, aasiyah
<alam_seher@hotmail-dot-com.no-spam.invalid> writes
Hi
if you would sketch how the voltage from the wall plug varies with
thime, how would it look like, how can you find it out?
Google "sine wave".
I know it has
something to do with three phase since it is in AC signal. (a wall
plug in Europe with three-phase, 50 Hz and 230V)
The 230V wall plug only yields one of the three phases.
--
Richard Herring
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| User: "Ken S. Tucker" |
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| Title: Re: how does voltage from a wall plug vary with time |
09 Feb 2005 07:04:08 AM |
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I got fucked one time ...ha ha...
I was building an electrical apparatus, requiring
two sources of AC. What I failed to realize is
some A/C is in counter phase so that the relative
hot wires have potential difference of 240 AC,
from room to room. I stupidly assumed the hot
(black wire) was the same potential throught out
the house. Not necessarily.
Anyway, I thought the fuckin fault was in the
apparatus I designed, took me 2 days to figure
out the design was ok...duh...
ding-bat
Ken
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| User: "" |
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| Title: Re: how does voltage from a wall plug vary with time |
09 Feb 2005 08:51:37 AM |
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It's a common code requirement to have heavy duty 120 volt outlets in a
kitchen. One way this is done is to run a 240 Volt line (ground plus
two live, 180 deg out of phase) to a single duplex outlet, and wire the
two 120 volt lines separately to the two halves of the duplex outlet.
The connector in the duplex outlet can be broken out to isolate the two
halves. You now have two single outlets, each on its own fuse/breaker.
I once saw the results of plugging an outlet multiplier (six outlets
from two) into an outlet wired like this. The multiplier tied the two
hot lines together! A 240 V dead short, in a device that you're pushing
on... A really bad day...
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| User: "Ken S. Tucker" |
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| Title: Re: how does voltage from a wall plug vary with time |
09 Feb 2005 08:02:23 PM |
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wrote:
It's a common code requirement to have heavy duty 120 volt outlets in
a
kitchen. One way this is done is to run a 240 Volt line (ground plus
two live, 180 deg out of phase) to a single duplex outlet, and wire
the
two 120 volt lines separately to the two halves of the duplex outlet.
The connector in the duplex outlet can be broken out to isolate the
two
halves. You now have two single outlets, each on its own
fuse/breaker.
I once saw the results of plugging an outlet multiplier (six outlets
from two) into an outlet wired like this. The multiplier tied the
two
hot lines together! A 240 V dead short, in a device that you're
pushing
on... A really bad day...
Those are handy do-dads, but they shouldn't tie
the black or white sides together, they should use
3 from the upper and 3 from the lower, kept separate.
BTW, you're right, about that 240 *****. I'm building
a house and ordered the electrical code book, to
wire the place and it's the phase specd in kitchens.
I do understand the load balance la-la-la you know
all about.
Thanks
Ken
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| User: "Androcles Androcles@ MyPlace.org" |
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| Title: Re: how does voltage from a wall plug vary with time |
10 Feb 2005 11:43:09 PM |
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"Ken S. Tucker" <dynamics@vianet.on.ca> wrote in message
news:1108000942.979282.176680@g14g2000cwa.googlegroups.com...
jmorriss@idirect.com wrote:
It's a common code requirement to have heavy duty 120 volt outlets in
a
kitchen. One way this is done is to run a 240 Volt line (ground plus
two live, 180 deg out of phase) to a single duplex outlet, and wire
the
two 120 volt lines separately to the two halves of the duplex outlet.
The connector in the duplex outlet can be broken out to isolate the
two
halves. You now have two single outlets, each on its own
fuse/breaker.
I once saw the results of plugging an outlet multiplier (six outlets
from two) into an outlet wired like this. The multiplier tied the
two
hot lines together! A 240 V dead short, in a device that you're
pushing
on... A really bad day...
Those are handy do-dads, but they shouldn't tie
the black or white sides together, they should use
3 from the upper and 3 from the lower, kept separate.
BTW, you're right, about that 240 *****. I'm building
a house and ordered the electrical code book, to
wire the place and it's the phase specd in kitchens.
I do understand the load balance la-la-la you know
all about.
Thanks
Ken
LOL, Try 440V 3 phase in Britain, 240V RMS single phase.
I once got both hands behind two buss-bars at 440V
and managed to get off by falling off the ladder. It tingles.
The upside was everyone wanted me to take a break and
have a cup of tea. So why not?
Androcles.
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| User: "Michael Moroney" |
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| Title: Re: how does voltage from a wall plug vary with time |
11 Feb 2005 10:19:58 AM |
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"Androcles" <Androcles@ MyPlace.org> writes:
LOL, Try 440V 3 phase in Britain, 240V RMS single phase.
I once got both hands behind two buss-bars at 440V
and managed to get off by falling off the ladder. It tingles.
The upside was everyone wanted me to take a break and
have a cup of tea. So why not?
Ouch!
Mathematically, the phase-phase voltage should be "only" 416 volts if
the single phase is 240V. Or 398V if 230V. (I've seen continental
power is usually described as being 230Y/400 volts)
Good thing, the extra 24V would have done you in!
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| User: "Androcles Androcles@ MyPlace.org" |
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| Title: Re: how does voltage from a wall plug vary with time |
11 Feb 2005 05:21:01 PM |
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"Michael Moroney" <moroney@world.std.spaamtrap.com> wrote in message
news:cuilve$grd$2@pcls4.std.com...
"Androcles" <Androcles@ MyPlace.org> writes:
LOL, Try 440V 3 phase in Britain, 240V RMS single phase.
I once got both hands behind two buss-bars at 440V
and managed to get off by falling off the ladder. It tingles.
The upside was everyone wanted me to take a break and
have a cup of tea. So why not?
Ouch!
Mathematically, the phase-phase voltage should be "only" 416 volts if
the single phase is 240V. Or 398V if 230V. (I've seen continental
power is usually described as being 230Y/400 volts)
Yeah... but remember we are talking nominal, actual voltages are
not exact. 415V was also quoted.
Good thing, the extra 24V would have done you in!
LOL, yeah. It did tickle. Trouble was, my hands clenched and
gripped even tighter.
I had to take my feet of the ladder and let myself fall.
Luckily it was only a 3-4 ft drop.
I decide not to work live after that.
On another occasion we had an apprentice working, and
we'd shut down and locked the breaker off, it was 11,000V.
The kid licked his finger and touched the bus-bar to see if
it was still live. :-)
Androcles.
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| User: "Ken S. Tucker" |
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| Title: Re: how does voltage from a wall plug vary with time |
11 Feb 2005 06:18:20 PM |
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No *****, I took 12000 VDC and died.
I was calibrating a cheap B&W CRT
but inadvertly contacted a test wire
used to calibrate the HV. When I came
to, CRT was heading toward the
floor. I suffered an instanteous and
total lack of conscious in that event,
I was equivalent to dead, everything
disappeared. I was even able to
understand my memory stopped
functioning, I yelled like a sissy when
that happened.
Ken
PS: That experience is not for twinks!!
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| User: "Androcles Androcles@ MyPlace.org" |
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| Title: Re: how does voltage from a wall plug vary with time |
11 Feb 2005 06:48:29 PM |
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"Ken S. Tucker" <dynamics@vianet.on.ca> wrote in message
news:1108167500.390507.264050@l41g2000cwc.googlegroups.com...
No *****, I took 12000 VDC and died.
I was calibrating a cheap B&W CRT
but inadvertly contacted a test wire
used to calibrate the HV. When I came
to, CRT was heading toward the
floor. I suffered an instanteous and
total lack of conscious in that event,
I was equivalent to dead, everything
disappeared. I was even able to
understand my memory stopped
functioning, I yelled like a sissy when
that happened.
Ken
PS: That experience is not for twinks!!
Spark plugs not grounded on the engine block are fun too,
but getting a metal wristwatch strap across a 12V car battery
makes the skin on your wrist peel off.
Androcles.
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| User: "Uncle Al" |
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| Title: Re: how does voltage from a wall plug vary with time |
09 Feb 2005 11:53:41 AM |
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aasiyah wrote:
Hi
if you would sketch how the voltage from the wall plug varies with
thime, how would it look like, how can you find it out? I know it has
something to do with three phase since it is in AC signal. (a wall
plug in Europe with three-phase, 50 Hz and 230V)
A one-phase outlet is a remarkably clean sine wave. A three-phase
plug is three remarkably clean sine waves with 120 degree phase
shift. 50 Hz voltage is incredibly stupid from generator to user.
Your fluorescent lights flicker and your transformers are less
efficient. A modestly higher multiple of 60 Hz would be better for
all.
Equipment connecting, running, and disconnecting from the line cause
reactance and capacitance glitches resulting in voltage spikes and
sags. That is one reason why you plug anything expensive into a very
good surge protector. Lightning and crass human stupidity (inclding
linesmen) are two other reasons.
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz.pdf
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| User: "tj Frazir" |
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| Title: Re: how does voltage from a wall plug vary with time |
10 Feb 2005 04:06:18 PM |
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If I sketch ,,each phase is a circle
and 3 phases will look like 3 circles overlapped
3 leads 3 phase..
single phase will be 2 leads 3 phase will be 3 leads and 110 ill be 1
lead and 1 common.
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
the volts will not drop to 0 as the overlap
points are at % up the circles.
if I drew a pic on paper.
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| User: "Michael Moroney" |
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| Title: Re: how does voltage from a wall plug vary with time |
09 Feb 2005 01:50:23 PM |
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Uncle Al <UncleAl0@hate.spam.net> writes:
A one-phase outlet is a remarkably clean sine wave. A three-phase
plug is three remarkably clean sine waves with 120 degree phase
shift. 50 Hz voltage is incredibly stupid from generator to user.
Your fluorescent lights flicker and your transformers are less
efficient. A modestly higher multiple of 60 Hz would be better for
all.
The current powerline frequencies were originally chosen as a compromise
between high enough to reduce flicker (in incandescent bulbs) and low
enough for large motors to run efficiently. Large motors of the time were
more efficient at lower frequency. Even today, there are a few railroads
in the US that use 20Hz electric (or is it 25Hz? I forget), and 16 2/3 Hz
in Europe for their electrified railroads. Are there still 20Hz
generators in use at Niagara Falls (Canadian side)?
Longer distance AC transmission becomes less stable with higher frequency.
The AC hum would become an annoying whine (ever notice the "A" note whine
on aircraft when taking a flight? It's their 400Hz AC power system)
The urban legend is that when asked what frequency should be used for new
AC power systems, Tesla came up with 60 Hz off the top of his head.
--
-Mike
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| User: "John Morriss" |
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| Title: Re: how does voltage from a wall plug vary with time |
09 Feb 2005 06:42:26 PM |
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(Michael Moroney) wrote in message news:<cudphv$ohf$1@pcls4.std.com>...
Uncle Al <UncleAl0@hate.spam.net> writes:
A one-phase outlet is a remarkably clean sine wave. A three-phase
plug is three remarkably clean sine waves with 120 degree phase
shift. 50 Hz voltage is incredibly stupid from generator to user.
Your fluorescent lights flicker and your transformers are less
efficient. A modestly higher multiple of 60 Hz would be better for
all.
The current powerline frequencies were originally chosen as a compromise
between high enough to reduce flicker (in incandescent bulbs) and low
enough for large motors to run efficiently. Large motors of the time were
more efficient at lower frequency. Even today, there are a few railroads
in the US that use 20Hz electric (or is it 25Hz? I forget), and 16 2/3 Hz
in Europe for their electrified railroads. Are there still 20Hz
generators in use at Niagara Falls (Canadian side)?
Longer distance AC transmission becomes less stable with higher frequency.
The AC hum would become an annoying whine (ever notice the "A" note whine
on aircraft when taking a flight? It's their 400Hz AC power system)
The urban legend is that when asked what frequency should be used for new
AC power systems, Tesla came up with 60 Hz off the top of his head.
Check out a physiology text-book, for a graph of "muscles-can't-move"
current vs frequency in human shock. Seems that 60 Hz is almost the
most dangerous frequency: locks the muscles at almost the lowest
current.
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| User: "tadchem" |
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| Title: Re: how does voltage from a wall plug vary with time |
09 Feb 2005 02:11:34 PM |
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Michael Moroney wrote:
<snip>
The urban legend is that when asked what frequency should be used for
new
AC power systems, Tesla came up with 60 Hz off the top of his head.
Like much of Tesla's thoughts, the details and reasoning for this are
unrecorded. Many of his personal notes have been lost - one way or
another.
It may be noted that Tesla made this recommendation at a time when he
was thinking about the possibility of broadcasting electrical power
world-wide, and after he had completed his studies in Colorado
concerning the properties of natural lightning.
A 60 Hz oscillation has a wavelength L of about 5000 km and would
excite a standing wave in a circular resonator 40000 km in
circumference C: C/L = 8. A 50 Hz oscillation would not: C/L = 6.6667.
Tom Davidson
Richmond, VA
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| User: "Nick Rouse" |
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| Title: Re: how does voltage from a wall plug vary with time |
11 Feb 2005 06:40:36 PM |
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Uncle Al <UncleAl0@hate.spam.net> wrote in message news:<420A4E25.357F5B08@hate.spam.net>...
aasiyah wrote:
Hi
if you would sketch how the voltage from the wall plug varies with
thime, how would it look like, how can you find it out? I know it has
something to do with three phase since it is in AC signal. (a wall
plug in Europe with three-phase, 50 Hz and 230V)
A one-phase outlet is a remarkably clean sine wave. A three-phase
plug is three remarkably clean sine waves with 120 degree phase
shift. 50 Hz voltage is incredibly stupid from generator to user.
Your fluorescent lights flicker and your transformers are less
efficient. A modestly higher multiple of 60 Hz would be better for
all.
Equipment connecting, running, and disconnecting from the line cause
reactance and capacitance glitches resulting in voltage spikes and
sags. That is one reason why you plug anything expensive into a very
good surge protector. Lightning and crass human stupidity (inclding
linesmen) are two other reasons.
Although 50Hz lighting may flicker in absolute terms more than 60Hz
the
difference is not nearly as much as is perceived by those who have
lived
most of their lives in 60Hz areas when visiting 50Hz areas.
Experiments have
shown that long exposure to one frequency of flicker causes a
distinct
notch in the visual frequency response. In visiting America from here
in Britain, I find the lighting somewhat more flickery that at home
but not as much as American friends visiting here who find it hard
to see how I put up with such lighting.
Transformers built for 50Hz are not less efficient than those built
for 60Hz.
but plug in a transformer built for 60Hz into a 50Hz supply and it
will heat
up more. If built to operate at the same maximum magnetic flux levels
(by having proportionately greater core cross section or
proportionally more primary
turns or a bit of both) a 50Hz transformer would be more efficient
than
a 60Hz one although bigger.
Even higher frequencies give much smaller devices but not necessarily
much cheaper as
steps have to be taken to keep the losses down. 400Hz aircraft
transformers tend to use very thin laminations of cobalt iron which is
many times more expensive than silicon steel used at 50 & 60 Hz
The cleanliness of the sinewaves is very dependant on the nature of
the
load in your vicinity. A largely linear load will leave the waveform
clean
but substantial non-linear loads such as discharge lighting,
rectifiers or
non-power factor corrected switched mode power supplies can distort
the
voltage waveform for other users substantially. 5% harmonic
distortion is quite
common close to sights where such loads make up a large fraction of
the
power used locally.
The original question asked about wall plugs (sockets) in Europe.
Anti-phase
live conductors are never found in domestic supplies (although
building
sites use portable transformers that transform 240 or 230V down to an
earthed
centre tapped 110V). As stated in an earlier post three phase supplies
are very rare here in domestic situations and in the few cases they
are used
they tend to be fixed wiring. I have not come across any three phase
sockets approved for use in Europe that you would want in your house.
Nick Rouse
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| User: "Dan Bloomquist" |
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| Title: Re: how does voltage from a wall plug vary with time |
09 Feb 2005 12:53:00 PM |
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Uncle Al wrote:
A one-phase outlet is a remarkably clean sine wave. A three-phase
plug is three remarkably clean sine waves with 120 degree phase
shift. 50 Hz voltage is incredibly stupid from generator to user.
Your fluorescent lights flicker and your transformers are less
efficient. A modestly higher multiple of 60 Hz would be better for
all.
60hz was settled on as high enough to get beyond the flicker level. But
in order to keep the losses down, the frequency needed to be kept as low
as possible. 400hz is popular where the power/weight ratio of motors
becomes important, like in aircraft.
Thanks to modern thyristors, DC is becoming popular for long hauls.
Best, Dan.
--
http://lakeweb.net
http://ReserveAnalyst.com
No EXTRA stuff for email.
What can you see if you can't see it all...
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| User: "pete" |
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| Title: Re: how does voltage from a wall plug vary with time |
10 Feb 2005 07:19:48 AM |
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aasiyah wrote:
Hi
if you would sketch how the voltage from the wall plug varies with
thime, how would it look like, how can you find it out? I know it has
something to do with three phase since it is in AC signal. (a wall
plug in Europe with three-phase, 50 Hz and 230V)
If you sketch it in AC, then it's a constant.
--
pete
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| User: "aasiyah" |
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| Title: re:how does voltage from a wall plug vary with time |
09 Feb 2005 10:30:04 AM |
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so from this graph http://en.wikipedia.org/wiki/Three_phase you would
say only one of these three voltages goes through a wall plug? How
does this work..
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| User: "CWatters" |
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| Title: Re: re:how does voltage from a wall plug vary with time |
10 Feb 2005 02:57:11 PM |
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"aasiyah" <alam_seher@hotmail-dot-com.no-spam.invalid> wrote in message
news:420a3a8c$1_2@127.0.0.1...
so from this graph http://en.wikipedia.org/wiki/Three_phase you would
say only one of these three voltages goes through a wall plug? How
does this work..
What do you mean how does this work?
All you need is one live (sine wave) and one neutral ("0V").
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