280V motor on 230V circuit
Deodiaus
fix
or repair.
While doing a search on the web, I found the same model (really cheap)
but
wired for 280V, instead of the 230 V load that my wiring is supplies.
Now, I was thinking of buying the cheap 280V model and installing it
instead. Aside from rotating at a different speed and
maybe some power inefficiencies, are there any other drawbacks of
using the 280V model
instead?
DaveM
news:2f85e038-fd1b-4f6c...@x41g2000hsb.googlegroups.com...
If it's the same model motor, you might be able to rewire it for your 230V
supply. Look at the nameplate or inside the wiring chamber to see if there is a
wiring diagram that details wiring connections for different voltages.
Barring that, you might search the Mfr's website (if they are still in business)
or Google for the make and model of your motor and see if there is any data on
it that details the wiring instructions.
--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters in the
address)
Some people are like Slinkies. Not really good for anything, but they bring a
smile to your face when pushed down the stairs.
way.off....@gmail.com
BUY IT! You'll thank yourself 10 years from now! The speed diffrence
wil be neglegable, the duty-cycle will be such that the motor will
enjoy a much longer life... if anything you could step-up RPM by
adding pulleys and a drive-belt rather than direct-drive coupled as it
is now... The pulley/belts would also minimize start-shock to the pump
by softening the inital roll in of the motor...
Michael A. Terrell
You mean the 120/208 VAC motor that was for sale on Ebay?
--
http://improve-usenet.org/index.html
Use any search engine other than Google till they stop polluting USENET
with porn and junk commercial SPAM
If you have broadband, your ISP may have a NNTP news server included in
your account: http://www.usenettools.net/ISP.htm
Jamie
hr(bob) hofmann@att.net
I'd be suspicious that the 280V was a misreading somehow of 230V.
Jamie
danny burstein
>>> are you sure it isn't 208 ?
>>>
>>>--http://webpages.charter.net/jamie_5"
>>
>>
>> I'd be suspicious that the 280V was a misreading somehow of 230V.
>that sounds more plausible.
Or... of 208V. If you have a "three phase" circuit
coming into a building, and you run two "hot" wires
to your appliance (or motor), the effective voltage
you're getting is 208V.
There's enough overlap so that a standard 240V appliance
such as, say, a larger air conditioner, will work more
or less ok on 208V. And vice versa.
But there is most assuredely a difference in the
two circuits, so for optimal results, you'll want
an appliance (or motor) designed for the specific
wiring in your facility.
--
_____________________________________________________
Knowledge may be power, but communications is the key
dan...@panix.com
[to foil spammers, my address has been double rot-13 encoded]
jakdedert
world does the utility supply 230v?
jak
"Blattus Slafaly ? (3) ¼ :)"
280vac is an odd rating, so it 230. 120/240 is standard single phase
ratings. 208 is three phase. If it's 208 don't get it.
--
Blattus Slafaly ? 3 :) 7/8
Don Kelly
"jakdedert" <jakd...@bellsouth.net> wrote in message
news:89RQj.52246$r76....@bignews8.bellsouth.net...
Depending on the age of the motor it could be rated 230V which now has crept
up to 240V just as once we had 110V, then 115V then 120V as nominal
voltages -(except for the radio people who settled on 117V and assumed that
that was what you got.).
--
Don Kelly dh...@shawcross.ca
remove the X to answer
Charles Foot
John G
"jakdedert" <jakd...@bellsouth.net> wrote in message
news:89RQj.52246$r76....@bignews8.bellsouth.net...
Most except the USA and Canada and a few others.
John G.
phil-new...@ipal.net
| I'm a little confused about a 230 volt circuit. In what part of the
| world does the utility supply 230v?
http://en.wikipedia.org/wiki/Mains_power_systems
There are two different flavors of 220/230/240 volts. Some places have a
simple system with one wire hot and one wire grounded. Other places have
a split system where the voltage is split in half to get 110/115/120 volts
relative to ground, by adding a additional "middle" conductor that is the
grounded one.
--
|WARNING: Due to extreme spam, I no longer see any articles originating from |
| Google Groups. If you want your postings to be seen by more readers |
| you will need to find a different place to post on Usenet. |
| Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) |
James Sweet
"DaveM" <mason...@comcast99.net> wrote in message
news:xPKdna3cPLk9CI7V...@comcast.com...
> "Deodiaus" <deod...@yahoo.com> wrote in message
> news:2f85e038-fd1b-4f6c...@x41g2000hsb.googlegroups.com...
>>I have a broken pool motor [magnetek y56y] which will cost a bundle to
>> fix
>> or repair.
>> While doing a search on the web, I found the same model (really cheap)
>> but
>> wired for 280V, instead of the 230 V load that my wiring is supplies.
>> Now, I was thinking of buying the cheap 280V model and installing it
>> instead. Aside from rotating at a different speed and
>> maybe some power inefficiencies, are there any other drawbacks of
>> using the 280V model
>> instead?
>
> If it's the same model motor, you might be able to rewire it for your 230V
> supply. Look at the nameplate or inside the wiring chamber to see if
> there is a wiring diagram that details wiring connections for different
> voltages.
> Barring that, you might search the Mfr's website (if they are still in
> business) or Google for the make and model of your motor and see if there
> is any data on it that details the wiring instructions.
>
> --
> Dave M
> MasonDG44 at comcast dot net (Just substitute the appropriate characters
> in the address)
>
What's broken on the original motor? There isn't a whole lot to go wrong
with these, I've yet to run into one I couldn't fix.
James Sweet
"Jamie" <jamie_ka1lpa_not_v...@charter.net> wrote in message
news:F_OQj.1657$F13....@newsfe07.lga...
Misreading of 208V undoubtably, 208 is very common in commercial buildings,
that and 277.
Arfa Daily
"jakdedert" <jakd...@bellsouth.net> wrote in message
news:89RQj.52246$r76....@bignews8.bellsouth.net...
In theory, it's 230 on a single phase - neutral circuit here in the UK now,
but in practice, it's actually nearer the previously accepted 240v for the
most part ...
Arfa
Baron
UK ! 230/240 V
--
Best Regards:
Baron.
Ulysses
"James Sweet" <james...@hotmail.com> wrote in message
news:yFWQj.134$_v1.102@trndny06...
Me too. Usually it's just been corrosion that can be cleaned off and/or
lack or lubrication.
You
wrote:
> There are two different flavors of 220/230/240 volts. Some places have a
> simple system with one wire hot and one wire grounded. Other places have
> a split system where the voltage is split in half to get 110/115/120 volts
> relative to ground, by adding a additional "middle" conductor that is the
> grounded one.
Sonny, you need to LEARN the difference between Ground and Neutral......
before you spout any further BS.......
operator jay
"You" <y...@shadow.orgs> wrote in message
news:you-D96DBC.0...@netnews.worldnet.att.net...
What he wrote looks reasonable to me in terms of ground and neutral.
Neutral is the grounded conductor where I live. He does not say to
use a ground as a neutral, if that's what you're getting at. I can
only guess that that may be what you're getting at, you haven't really
said.
[trimmed sci.physics.electromag]
j
phil-new...@ipal.net
He might be one of those "knows just enough to be really dangerous" people
on the net. I didn't even mention "neutral". My intent was to explain it
in a simpler way for someone to just understand the basic difference. The
term "middle" was to convey a little more information than "neutral" would
have ... for the targeted audience.
There were two reasons Edison used a split system. One was to get the
advantage of less voltage drop and/or longer wires. The other was to run
the light bulbs on a lower voltage, which he knew makes them more reliable.
If he had not been fixated on DC, and had simply accepted AC early on, he
might well have discovered that an even lower voltage made the bulbs even
more reliable, and that a step down transformer at each building would have
done the job reliably, and also allow him to distribute at a higher voltage.
For example, he could have distributed at 600 volts and stepped down to 30
volts inside each building (maybe on a floor by floor basis). OTOH, he could
have run a DC motor-generator to get a lower voltage, too (though it would
have been less reliable than a transformer on AC). Had the light bulb voltage
issue not been a factor, he might well have simply run a straight 2-wire 220
volt system.
phil-new...@ipal.net
Is the grounded conductor in a 2-wire 230/240 volt system fed to each home
referred to as "neutral" even in UK?
phil-new...@ipal.net
And where you have 277 you almost certainly have 480. But I suppose it is
possible to have 277 alone (is better to use than 120 for lots of fluorescent
lighting) or maybe even a 554/277 Edison style single phase split system,
where three phase distribution is not available and the higher voltage is
desirable for large areas of commercial lighting.
charles
<phil-new...@ipal.net> wrote:
>
> Is the grounded conductor in a 2-wire 230/240 volt system fed to each home
> referred to as "neutral" even in UK?
Yes. - but where is it grounded. Formerly it was grounded only at the
star (centre) point of the local transformer, but more recently is it being
grounded (again) at the domestic intake point.
--
From KT24 - in "Leafy Surrey"
Using a RISC OS computer running v5.11
Andrew Gabriel
phil-new...@ipal.net writes:
> In alt.engineering.electrical Arfa Daily <arfa....@ntlworld.com> wrote:
>|
>| "jakdedert" <jakd...@bellsouth.net> wrote in message
>| news:89RQj.52246$r76....@bignews8.bellsouth.net...
>|> does the utility supply 230v?
>|>
>|> jak
>|
>| In theory, it's 230 on a single phase - neutral circuit here in the UK now,
>| but in practice, it's actually nearer the previously accepted 240v for the
>| most part ...
>
> Is the grounded conductor in a 2-wire 230/240 volt system fed to each home
> referred to as "neutral" even in UK?
Yes, although we have 3 types of supply arrangement for earthing
used on public supplies. (Note that on 240V, there's often far
more distance between the consumer and the transformer than
you'll find in the US on 120V supplies.)
TN-S:
Neutral is grounded only at the transformer, but a separate
earth conductor is carried in the supply network and brought
into the home from that same grounding point.
TN-C-S (also known as Protective Multiple Earthing):
A single PEN (Protective Earth and Neutral) conductor from
the transformer serves as both neutral and ground connection
in the supply network. The PEN conductor must also be earthed
regularly throughout the supply network, and it requires very
high integrity connections to ensure the risk of it breaking
is very low (this is a legal requirement). Once the supply
reaches the consumer, the PEN conductor is split into separate
neutral and earth conductors in the installation.
TT:
The supplier grounds the neutral as for TN-S, but doesn't
provide the consumer with any earthing connection. The
consumer needs to make their own ground connection for earthing
(and shouldn't cross-connect this to the neutral).
TT is only found on old rural overhead supply networks, and
they are upgraded to TN-C-S when due for refurbishment.
Even if the supplier does provide an earth connection (TN-S
or TN-C-S), the installation can choose to ignore it and be
wired as a TT system. This is sometimes done for submains
to outbuildings and outdoor electrics, even when the main
installation is TN-S or TN-C-S.
These earthing system arrangements are covered in the uk.d-i-y
FAQ: http://www.diyfaq.org.uk/electrical/electrical.html#system
--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]
Arfa Daily
<phil-new...@ipal.net> wrote in message
news:fv2ip...@news4.newsguy.com...
One common neutral that is grounded back at the nearest transformer
substation, and three phases, fed singly to homes in a reasonably 'balanced'
way (loading-wise). So one side of the street may be fed from one phase, and
the other side of the street from a different phase, then further up the
street, some more houses connected to the remaining phase and so on. Each
house also has a protective ground connection. Generally, no 'pole pigs'
except in rural areas. For the most part, each collection of several hundred
houses, are connected underground to a small building containing 3 phase
transformers. I think that the input to these stations is around 11kV, also
underground. The 'hot' side of the supply is usually known as "live" in the
UK, but is sometimes also known as "phase".
I'm not an electrical engineer, but that's pretty much the basis of the UK
domestic distribution system. Commercial premises usually have a full three
phase plus neutral connection to the network.
Arfa
Michael Kennedy
<phil-new...@ipal.net> wrote in message
news:fv2im...@news4.newsguy.com...
Well, I understood what he meant, but maybe I took it the wrong way. When he
said middle conudctor I was thinking the center lug on the transformer which
is grounded and used as the neutral.
Mike
Michael Kennedy
"Andrew Gabriel" <and...@cucumber.demon.co.uk> wrote in message
news:4814d978$0$659$5a6a...@news.aaisp.net.uk...
In the USA they ground the Neutral at the transformer and do not run
a seperate ground conductor to the house. There is however a ground
rod driven which is tied to the neutral at the entrance to the house.
]
Deodiaus
pump because it was rusted shut and bolted on well.
The repair guy said it was a break in the winding. He is rewinding it
for $170.
I was thinking of doing it myself but I was told that rewinding it
manually is tough.
BTW, I cannot refind the "for sale" motor on the web anymore.
phil-new...@ipal.net
That is what I meant when I said middle conductor. I intentionally avoided
calling it neutral for the person I was responding to. I did quote it to
make it clear (but this apparently was not clear enough for at least one
person) for others that I was using some other term.
phil-new...@ipal.net
| Yes, although we have 3 types of supply arrangement for earthing
| used on public supplies. (Note that on 240V, there's often far
| more distance between the consumer and the transformer than
| you'll find in the US on 120V supplies.)
Our supplies to homes are also 240V. We just ground it in a different
way through the use of a center tap and an additional wire, which gets
the neutral designation. For an equivalent _balanced_ load in the US,
we should see no more voltage drop than in the UK. And that voltage
drop will be effectively halved between one of the hots and the neutral.
Nice info!
I'm curious about this: is it legal in the UK for a home to feed their supply
into their own transformer and ground the secondary at that point as a new
system?
JANA
call 220 or 230 VAC in your home is actually 208 VAC, unless you
installed some kind of transformer to compensate.
I somehow think that the vendor of the motor made an error. Having 280
VAC sounds to me very unconventional, unless this was some kind of
special installation.
I would buy the motor. If in the even that it needed a higher voltage
because it lacks torque for your application, then there is the
possibility of needed an transformer. This would be expensive.
Some motors have a cover plate inside with strappings, to allow changing
its operating voltage, RPM, and direction of rotation.
If you were to run a synchronous motor on a lower voltage, it will have
lower torque rather than lower RPM, unless the supply voltage was
reduced to below the motor's stable operating threshold. Synchronous
motors are dependent on the AC frequency (Hz) for their RPM.
--
JANA
_____
"Deodiaus" <deod...@yahoo.com> wrote in message
news:2f85e038-fd1b-4f6c...@x41g2000hsb.googlegroups.com...
James Sweet
"JANA" <ja...@NOSPAMca.inter.net> wrote in message
news:meWdnTMrMd-EXovVnZ2dnUVZ_tGonZ2d@uniservecommunications...
> If you are in North America, and have 120 VAC to the outlets, what you
> call 220 or 230 VAC in your home is actually 208 VAC, unless you
> installed some kind of transformer to compensate.
>
No, that's not true. It's 240V, the transformer has a grounded center tap so
120 from either side to neutral, and 240 between the hots. You find 208V in
commercial buildings and some apartment complexes that are fed with 3 phase,
but not in a house, unless you're one of the few lucky people to have 3
phase available.
> I somehow think that the vendor of the motor made an error. Having 280
> VAC sounds to me very unconventional, unless this was some kind of
> special installation.
>
It's clearly a typo and should be 208V.
Arfa Daily
If it's not a silly question, with the motor in question being offered "on
the web, really cheap", then if it's e-bay, why not use the 'ask the seller
a question' option, or if it's a reseller, use his on-site 'contact us'
facility ? Then there would be no debate about typos and exotic voltage
issues ... :-)
Arfa
Benj
> I tried first by replacing the capacitor. I could not pry off the
> pump because it was rusted shut and bolted on well.
This is standard with "pool stuff" around water.
> The repair guy said it was a break in the winding. He is rewinding it
> for $170.
> I was thinking of doing it myself but I was told that rewinding it
> manually is tough.
He is right, it is.
> BTW, I cannot refind the "for sale" motor on the web anymore.
Here's the first lesson in "shopping like a woman": Ya snooze, Ya
loose!
You see that "good price" you MUST buy it right then and there. If you
futz around trying to make up your mind, it'll always be too late!
Later it will be gone. [Hey, you think there's nobody else out there
who can spot a bargain like you?]
Bob F
"Arfa Daily" <arfa....@ntlworld.com> wrote in message news:TQARj.75480
> If it's not a silly question, with the motor in question being offered "on the
> web, really cheap", then if it's e-bay, why not use the 'ask the seller a
> question' option, or if it's a reseller, use his on-site 'contact us' facility
> ? Then there would be no debate about typos and exotic voltage issues ... :-)
Because it's long gone.
Neon John
>If you are in North America, and have 120 VAC to the outlets, what you
>call 220 or 230 VAC in your home is actually 208 VAC, unless you
>installed some kind of transformer to compensate.
Nope. The NA standard residential voltage is 120/240 single phase. 120/208
only happens when the single phase power is derived from a 3 phase
wye-connected transformer bank. The only place I've heard of that happening
on a regular basis is in high-rise apartments.
For smaller buildings, the split delta configuration is more common. This
supplies 120/240 single phase and 240 three phase from one 3-transformer bank.
This is also sometimes known as the "wild leg" configuration because the leg
not associated with the single phase supply has a odd voltage to
neutral/ground. Something like 214 volts if my memory holds.
John
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com <-- best little blog on the net!
Tellico Plains, Occupied TN
I like you ... you remind me of me when I was young and stupid.
phil-new...@ipal.net
| If you are in North America, and have 120 VAC to the outlets, what you
| call 220 or 230 VAC in your home is actually 208 VAC, unless you
| installed some kind of transformer to compensate.
That's only true if the source transformer is a three phase WYE/star type.
If you have center tapped delta three phase, or single phase Edison split,
then you have genuine 240 volts (although with that delta you may also have
a third wire that is 208 volts relative to ground/neutral).
| I somehow think that the vendor of the motor made an error. Having 280
| VAC sounds to me very unconventional, unless this was some kind of
| special installation.
It may be a reference to working on 277 volts, which is an available voltage
in some large commercial/industrial locations.
z
wrote:
> On Apr 26, 6:14 pm, Jamie
>
>
>
>
>
> <jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:
> > Deodiaus wrote:
> > > fix
> > > or repair.
> > > While doing a search on the web, I found the same model (really cheap)
> > > but
> > > wired for 280V, instead of the 230 V load that my wiring is supplies.
> > > Now, I was thinking of buying the cheap 280V model and installing it
> > > instead. Aside from rotating at a different speed and
> > > maybe some power inefficiencies, are there any other drawbacks of
> > > using the 280V model
> > > instead?
>
>
> - Show quoted text -
yeah, where do you find 280 volts? it's either 208 or 230.
Tzortzakakis Dimitrios
? "Deodiaus" <deod...@yahoo.com> ?????? ??? ??????
news:2f85e038-fd1b-4f6c...@x41g2000hsb.googlegroups.com...
>I have a broken pool motor [magnetek y56y] which will cost a bundle to
> fix
> or repair.
> While doing a search on the web, I found the same model (really cheap)
> but
> wired for 280V, instead of the 230 V load that my wiring is supplies.
> Now, I was thinking of buying the cheap 280V model and installing it
> instead. Aside from rotating at a different speed and
> maybe some power inefficiencies, are there any other drawbacks of
> using the 280V model
> instead?
like the ones used in short duty appliances, like drills and blenters, will
rotate slower in lower voltages, without problems, Asynchronous motors
(brushless) will really smoke to death if used in voltages significantly
lower than nominal. Can't you find a generic pool motor, if you know the
horsepower, voltage (3 phase? line to line) and intake and outlet gauge? and
maybe rpm?
HTH,
--
Tzortzakakis Dimitrios
major in electrical engineering
mechanized infantry reservist
hordad AT otenet DOT gr
Tzortzakakis Dimitrios
Ο <phil-new...@ipal.net> έγραψε στο μήνυμα
news:fv5jc...@news2.newsguy.com...
MV (medium voltage) 20 kV for 60 km. HV (high voltage) 150 kV for 220 km.
EHV 400kV for 500 km with stability issues. 110 volt is so low you need a
transformer outside each building....
James Sweet
>> --
> Nope. LV (low voltage)230-V in Europe is just sufficient for 1 km
> distance. MV (medium voltage) 20 kV for 60 km. HV (high voltage) 150 kV
> for 220 km. EHV 400kV for 500 km with stability issues. 110 volt is so low
> you need a transformer outside each building....
>
>
>
> --
> Tzortzakakis Dimitrios
> major in electrical engineering
> mechanized infantry reservist
> hordad AT otenet DOT gr
>
Learn the system before you criticize it.
It's not 110V, it's 240V, we simply split it with a grounded center tap
which gives 120V between each side and neutral, or 240V between the sides..
There's no transformer per house, except rural applications. Generally 5-10
houses are on each transformer, sometimes more. The problem with long runs
is that the voltage fluctuates substantially with large loads such as
central air conditioning. Standard North American residential service is 200
Amps 240V, I gather this is quite a bit larger than typical European
domestic stuff, so stretching it over 1km distance would require
prohibitively large cables or suffer from wide voltage swings. Makes more
sense to run 7200V down the street and locate a smallish transformer near
every half dozen houses.
John Taylor
> Jamie wrote:
> > hr(bob) hof...@att.net wrote:
> >
> >> On Apr 26, 6:14 pm, Jamie
> >> <jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:
> >>
> >>> Deodiaus wrote:
> >>>
> >>>> I have a broken pool motor [magnetek y56y] which will cost a bundle to
> >>>> fix
> >>>> or repair.
> >>>> While doing a search on the web, I found the same model (really cheap)
> >>>> but
> >>>> wired for 280V, instead of the 230 V load that my wiring is supplies.
> >>>> Now, I was thinking of buying the cheap 280V model and installing it
> >>>> instead. Aside from rotating at a different speed and
> >>>> maybe some power inefficiencies, are there any other drawbacks of
> >>>> using the 280V model
> >>>> instead?
> >>>
> >>> are you sure it isn't 208 ?
> >>>
> >>> --http://webpages.charter.net/jamie_5"
> >>
> >>
> >> I'd be suspicious that the 280V was a misreading somehow of 230V.
> > that sounds more plausible.
> >
> I'm a little confused about a 230 volt circuit. In what part of the
> world does the utility supply 230v?
Most countries are 230 Volts (50 Hz) with some exceptions, such as North
America, parts of South America, Japan, and a few others. Nearly all of Europe
is standardized on 230 Volts 50 Hz, although outlet/plug shapes still vary from
country to country.
Tzortzakakis Dimitrios
Ο "James Sweet" <james...@hotmail.com> έγραψε στο μήνυμα
news:WMGTj.5083$ch1.2983@trndny09...
>
>
>>> --
>> Nope. LV (low voltage)230-V in Europe is just sufficient for 1 km
>> distance. MV (medium voltage) 20 kV for 60 km. HV (high voltage) 150 kV
>> for 220 km. EHV 400kV for 500 km with stability issues. 110 volt is so
>> low you need a transformer outside each building....
>>
>>
>>
>> --
>> Tzortzakakis Dimitrios
>> major in electrical engineering
>> mechanized infantry reservist
>> hordad AT otenet DOT gr
>>
>
>
> Learn the system before you criticize it.
>
> It's not 110V, it's 240V, we simply split it with a grounded center tap
> which gives 120V between each side and neutral, or 240V between the sides.
USA. I have worked, though in the decommisioned US base in Gournes, really
impressive your distribution systems:-)
And in Europe we have 400 V (3 phase) line to line voltage. It's 230 line to
earth. Large motors and conditioners use 3 phase. Normal residence is 40 A
230 V single phase, or for energy hogs 400 V 3 X 40 A 3 phase..
Thomas Tornblom
I also noticed just last week that Malaysia and Singapore use 230V (@50Hz).
Thomas Tornblom
or lower.
Room outlets are wired with one phase, neutral and ground to get 230V.
There is a smallish transformer station in the neighborhood which
probably powers two entire blocks. I would guess somewhere around 20-30
houses.
Tzortzakakis Dimitrios
? "Thomas Tornblom" <tho...@Hax.SE> ?????? ??? ??????
news:x04p97a...@Hax.SE...
german Schutzkontakt, security contact. There is a larger substation, maybe
2-3 for a city (in Iraklion we have 3, 180,000 residents) that steps down
from the transmission voltage, 150 kV down to primary distribution voltage,
15 kV that is the distributed with cables buried in earth. Our local power
station has units with 15 kV (older) and newer with 6.6 kV alternators, all
is stepped up to 150 kV even for the ~15 km to Iraklion. In capitals, like
Athens, electricity comes at 400 kV, is stepped down to 150 kV for secondary
transmission, again goes to the areas af the city with underground cables,
stepped down to 15 kV locally, and then distributed again (the main
generation facilities are in Kozani, West Macedonia, and they burn brown
coal. Typical size of a unit is 300 MW, voltage 21 kV and current 10 kA
which is stepped up to 400 kV, 400 A line current for transmission to Athens
and Thessaloniki).
Andrew Gabriel
Similar in UK.
In most European countries, there's a single phase current limit,
above which you have to take a 3-phase supply. In the UK, that's
100A, so it's not very common to have a 3-phase supply although
you can ask for one if you want a 3-phase supply. In some other
European countries, the single phase limit is as low as 20A, so
just about everyone has a 3-phase supply.
Residential substation transformers (11kV down to 230/400) are
usually 1MVA, feeding a number of streets. A substation may have
more than one transformer in some cases (although they usually
only start out with one). Obviously, smaller transformers are
used where there aren't so many houses, and these are sometimes
pole mounted if the wiring is overhead.
Andrew Gabriel
"James Sweet" <james...@hotmail.com> writes:
>
> It's not 110V, it's 240V, we simply split it with a grounded center tap
> which gives 120V between each side and neutral, or 240V between the sides..
It's the regulation at 120V which people notice.
If you want to call it a 240V supply, then you
need to call EU supplies 400V or 415V. That's
equally misleading.
> There's no transformer per house, except rural applications. Generally 5-10
> houses are on each transformer, sometimes more. The problem with long runs
> is that the voltage fluctuates substantially with large loads such as
> central air conditioning. Standard North American residential service is 200
> Amps 240V, I gather this is quite a bit larger than typical European
> domestic stuff, so stretching it over 1km distance would require
> prohibitively large cables or suffer from wide voltage swings. Makes more
> sense to run 7200V down the street and locate a smallish transformer near
> every half dozen houses.
The transformers are small in comparison, which gives poor
regulation in comparison (and as I said before, it's the
regulation at 120V which is the primary concern -- regulation
of 240V across 2 hots doesn't matter much for typical US 240V
loads).
James Sweet
>
> The transformers are small in comparison, which gives poor
> regulation in comparison (and as I said before, it's the
> regulation at 120V which is the primary concern -- regulation
> of 240V across 2 hots doesn't matter much for typical US 240V
> loads).
>
Regardless, the regulation is very good. I monitored mine for a while
and never saw it dip below 118V or go above 122V, most of the time it
was just about spot on 120V. A friend in the UK was doing the same on
his and it went as low as 224V and as high as 246V. We've done a lot of
comparing and have agreed that neither system is inherently better or
worse than the other, both have advantages and disadvantages.
charles
> Similar in UK.
or, as in the case of the transformer that feeds my house, pole mounted in
field with the output cables going underground immediately.
--
From KT24 - in "Leafy Surrey"
Using a RISC OS computer running v5.11
phil-new...@ipal.net
| "James Sweet" <james...@hotmail.com> writes:
|>
|> It's not 110V, it's 240V, we simply split it with a grounded center tap
|> which gives 120V between each side and neutral, or 240V between the sides..
|
| It's the regulation at 120V which people notice.
| If you want to call it a 240V supply, then you
| need to call EU supplies 400V or 415V. That's
| equally misleading.
The effect of loading and how it affects voltage depends on how well balanced
the TWO 120 volts phases are. If they are in balance, then the effect of the
loading on the voltage works as if you were considering the voltage at 240 volts.
If you get a three phase supply, and keep it balanced with the single phase
line to neutral loads, then the voltage regulation is going to be just like you
had loaded it with line-to-line loads, 208 volts in North America and 400 volts
in Europe.
If your neighborhood transformer is three phase, even if your home gets only
one phase of it (at just 230 volts), you still get advantage because other
homes will be distributed over other phases to keep it in balance.
But if you are comparing a single phase system, North American 120/240 with
three wires, vs. European 230 with two wires, it works out to be about the
same. The difference is we pay more for the extra wire, but we have a lower
line to ground shock risk (which isn't really much of an issue anymore with
improvements in safety in various ways such as GFI/RCD protection, better
rules on installations, etc).
So if you moved from Europe where you had 400/230 volts three phase in your
home, and came to North American and discovered we really had 480/277 volts
three phase, would that trouble you (assuming all appliances were designed
for that)?
Tzortzakakis Dimitrios
? "Andrew Gabriel" <and...@cucumber.demon.co.uk> ?????? ??? ??????
news:48246da4$0$657$5a6a...@news.aaisp.net.uk...
the HV side of the transformers, thus at 150 kV. Typical current for 2 x 25
MVA transformers is 150 A, 150 kV and of course secondary at 15 kV, 1500 A.
The regulation is done automatically with tap changers, live. The local
transformers at your neighborhood are fixed tap, 15 kV (they intend to
change everything to 20 kV).
Andrew Gabriel
I'm referring to the transformer regulation (and also the LV
supply cable voltage drop) response to load changes. E.g. if
I switch on my 10kW shower, that's a 0.1% change against the
max load of my 1MVA substation transformer and therefore
makes no perceivable difference to the voltage in my house.
If I were to try that on a US 50kVA transformer, that load
is going to trigger a change of 20% of the transformer
regulation, which is much more significant and would
certainly be visible as a brightness change in light bulbs.
Having lived in both countries, I would say it's pretty much
expected in the US that lights dim even with quite moderate
loads coming on, whereas it's rare in the UK (generally only
in rural areas with long supply lines). There are many
contributory factors to this difference, but the 120V verses
240V (or if you must, 240V verses 415V) is ultimately the
underpinning reason.
Automatic tap changing in the HV network is completely
invisible to the residential consumer, as indeed it should
be.
phil-new...@ipal.net
| I'm referring to the transformer regulation (and also the LV
| supply cable voltage drop) response to load changes. E.g. if
| I switch on my 10kW shower, that's a 0.1% change against the
| max load of my 1MVA substation transformer and therefore
| makes no perceivable difference to the voltage in my house.
| If I were to try that on a US 50kVA transformer, that load
| is going to trigger a change of 20% of the transformer
| regulation, which is much more significant and would
| certainly be visible as a brightness change in light bulbs.
What is the available fault current in these situations?
--
|WARNING: Due to extreme spam, googlegroups.com is blocked. Due to ignorance |
| by the abuse department, bellsouth.net is blocked. If you post to |
| Usenet from these places, find another Usenet provider ASAP. |
Michael A. Terrell
Tzortzakakis Dimitrios wrote:
>
> The regulation, at least in Europe, is done at 150/15 kV substations and at
> the HV side of the transformers, thus at 150 kV. Typical current for 2 x 25
> MVA transformers is 150 A, 150 kV and of course secondary at 15 kV, 1500 A.
> The regulation is done automatically with tap changers, live. The local
> transformers at your neighborhood are fixed tap, 15 kV (they intend to
> change everything to 20 kV).
So they have developed 100% efficient transformers?
--
http://improve-usenet.org/index.html
Use any search engine other than Google till they stop polluting USENET
with porn and junk commercial SPAM
If you have broadband, your ISP may have a NNTP news server included in
your account: http://www.usenettools.net/ISP.htm
Michael A. Terrell
The central air kicks on without my lights dimming, and I am in North
Central Florica.
>
> Automatic tap changing in the HV network is completely
> invisible to the residential consumer, as indeed it should
> be.
>
> --
> Andrew Gabriel
> [email address is not usable -- followup in the newsgroup]
James Sweet
>
> The central air kicks on without my lights dimming, and I am in North
> Central Florica.
>
>
Mine dim slightly for an instant when my 3 ton heat pump kicks in, it's
only noticeable with the few incandescent lights left in the house
though. The LRA on that thing is something like 90A. I think most of the
drop must be in the 50' or so of 2/0 AL wire between the meter base and
the transformer though as they don't seem to dim at all from any of the
neighbors.
You
"Michael A. Terrell" <mike.t...@earthlink.net> wrote:
> So they have developed 100% efficient transformers?
Yep, their called Super Conducting Transformers, and they have been
around the LABS, for about 15 years now. Only one BIG problem with them.
They only work at 20 Degrees Kevin or lower in temperature.
phil-new...@ipal.net
| The central air kicks on without my lights dimming, and I am in North
| Central Florica.
I bet it's on its own branch circuit, too.
James Sweet
phil-new...@ipal.net wrote:
> In alt.engineering.electrical Michael A. Terrell <mike.t...@earthlink.net> wrote:
>
> | The central air kicks on without my lights dimming, and I am in North
> | Central Florica.
>
> I bet it's on its own branch circuit, too.
>
Of course it is, that's the only legal way to do it.
Michael A. Terrell
>
> In alt.engineering.electrical Michael A. Terrell <mike.t...@earthlink.net> wrote:
>
> | The central air kicks on without my lights dimming, and I am in North
> | Central Florica.
>
> I bet it's on its own branch circuit, too.
So what? The meter is on a pole on one side of the driveway ( two
feet from the property line, because Progress Energy does not allow
drops to cross a driveway anymore.), and an outdoor breaker box is on
the remaining four foot stump of the old pole on the other side of the
paved drive, about 40 feet away. The 60 A breaker for the AC is in that
box, along with the 100 A main breaker that is used as a disconnect for
the house. That box is over 125 feet from the pole pig, on a 150 A
service. That box also feeds another underground line to the laundry
building,, and well pump. The main breaker box for the house is another
20 feet from the outdoor box. Now, tell me how it can have no effect on
the line voltage. I still see very little flickering, usually only on
hot summer days when everyone in the subdivision is using the AC and
their kitchen stoves at the same time. That is usually followed by a
blown 60 A fuse in the 7200 volt line, feeding my street.
--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.
Michael A. Terrell
Central Florida
phil-new...@ipal.net
| phil-new...@ipal.net wrote:
|>
|> In alt.engineering.electrical Michael A. Terrell <mike.t...@earthlink.net> wrote:
|>
|> | The central air kicks on without my lights dimming, and I am in North
|> | Central Florica.
|>
|> I bet it's on its own branch circuit, too.
|
|
| So what? The meter is on a pole on one side of the driveway ( two
| feet from the property line, because Progress Energy does not allow
| drops to cross a driveway anymore.), and an outdoor breaker box is on
| the remaining four foot stump of the old pole on the other side of the
| paved drive, about 40 feet away. The 60 A breaker for the AC is in that
| box, along with the 100 A main breaker that is used as a disconnect for
| the house. That box is over 125 feet from the pole pig, on a 150 A
| service. That box also feeds another underground line to the laundry
| building,, and well pump. The main breaker box for the house is another
| 20 feet from the outdoor box. Now, tell me how it can have no effect on
| the line voltage. I still see very little flickering, usually only on
| hot summer days when everyone in the subdivision is using the AC and
| their kitchen stoves at the same time. That is usually followed by a
| blown 60 A fuse in the 7200 volt line, feeding my street.
If it were not on its own branch circuit, that would (in addition to being
a code violation) more likely cause other stuff (whatever else is on the
same circuit) to experience dimming. The fact that it is onis own branch
circuit doesn't mean there isn't a big voltage drop. But only the A/C would
be getting it, and it wouldn't matter (much).
It can have no (or very little that cannot be noticed) effect on the line
voltage because you have good wiring and the transformer has a high enough
capacity and low enough impedance. This is stuff you know.
Blowing a 60 amp fuse at 7200 volts is not a small neighborhood.
I can understand them not wanting to go overheard over a driveway. RVs can
be a fun place for kids to climb on (even if terribly unsafe). Or they can
catch fire (I've seen that happen and it _was_ a case of a service drop over
a driveway that faulted when the insulation melted off).
Michael A. Terrell
48 lots, 47 with homes. That gives 7200*60/240 or 1800 A @ 240 V for
47 homes gives an average 38.29 A per home which is the reason that fuse
can blow more than once a week, along with it's explosive discharge that
sounds like a shotgun every time it blows.
> I can understand them not wanting to go overheard over a driveway. RVs can
> be a fun place for kids to climb on (even if terribly unsafe). Or they can
> catch fire (I've seen that happen and it _was_ a case of a service drop over
> a driveway that faulted when the insulation melted off).
At one time there were two meters on the property, because the
original owner had a blacksmith shop in the 1200 Sq Ft garage.
phil-new...@ipal.net
Yup, big neighborhood. It wouldn't take much after 47 home central A/C's
are running to go over the fuse rating. Any guess what the curve on that
fuse is? E.g. how long can you go at 105%? 125%?
Tzortzakakis Dimitrios
? "Michael A. Terrell" <mike.t...@earthlink.net> ?????? ??? ??????
news:KridndAr1fGpnLvV...@earthlink.com...
>
> Tzortzakakis Dimitrios wrote:
>>
>> The regulation, at least in Europe, is done at 150/15 kV substations and
>> at
>> the HV side of the transformers, thus at 150 kV. Typical current for 2 x
>> 25
>> MVA transformers is 150 A, 150 kV and of course secondary at 15 kV, 1500
>> A.
>> The regulation is done automatically with tap changers, live. The local
>> transformers at your neighborhood are fixed tap, 15 kV (they intend to
>> change everything to 20 kV).
>
>
> So they have developed 100% efficient transformers?
>
Of course not:-) These are approximate figures (like the 21 kV 10 kA
alternator, which in fact is 9823 A 21200 volts or whatever). But the
efficiency of large transformers or transmission lines, when they operate at
optimum is 99%.
daestrom
"Tzortzakakis Dimitrios" <no...@nospam.void> wrote in message
news:g04cc6$edo$1...@mouse.otenet.gr...
>
> ? "Andrew Gabriel" <and...@cucumber.demon.co.uk> ?????? ??? ??????
> news:48246da4$0$657$5a6a...@news.aaisp.net.uk...
>> The transformers are small in comparison, which gives poor
>> regulation in comparison (and as I said before, it's the
>> regulation at 120V which is the primary concern -- regulation
>> of 240V across 2 hots doesn't matter much for typical US 240V
>> loads).
> The regulation, at least in Europe, is done at 150/15 kV substations and
> at the HV side of the transformers, thus at 150 kV. Typical current for 2
> x 25 MVA transformers is 150 A, 150 kV and of course secondary at 15 kV,
> 1500 A. The regulation is done automatically with tap changers, live. The
> local transformers at your neighborhood are fixed tap, 15 kV (they intend
> to change everything to 20 kV).
>
>
You're confusing two uses of the term 'regulation'. Tap changers and
voltage regulators actively sense the terminal voltage and adjust
'something' to maintain the voltage within some design limit. That's a
'regulator' and provides 'regulation' of the sensed voltage.
But 'regulation' also is a term used to describe the inherent voltage drop
in some devices. For example, if you review DC generators, you'll find that
simple shunt-wound generators have fairly good 'regulation' and their output
voltage only drops a few percent from no-load to full-load when supplied
with a fixed field. A cumulatively-compound DC generator (which has a
series field and a shunt field), can have a nearly flat voltage curve from
no-load to full-load with just a fixed shunt excitation, or even have a
voltage rise depending on the degree of compounding. (of course, an active
voltage regulator can counteract whatever inherent regulation a machine may
have)
In the case of simple fixed-tap transformers, the term 'regulation' can be
used to describe how much the output terminal voltage changes from no-load
to full-load if the primary voltage is held constant. This use is less than
perfect as it is much better to use the transformer's impedance along with
the load's power factor to get a more precise answer.
In the US, voltage regulation is accomplished with load-tap-changers,
capacitor banks, and other 'voltage support services'. But just like in
Europe, it is done at the substation or higher level and not done at the
typical distribution transformer. There are exceptions for rural areas
though where the line length of the primary leads to some issues.
daestrom
P.S. In the US, a 'tap-changer' may be built for either for unloaded or
loaded operation. The 'unloaded' type can not be stepped to another tap
while there is load on the unit (although it can still be energized). It's
switch contacts cannot interrupt load though, so if you try to move it while
loaded, you can burn up the tap-changer. The classic 'load-tap-changer' is
actually several switches that are controlled in a precise sequence to shift
the load from one tap of the transformer to another while not interrupting
the load current.
P.P.S. Load tap changers typically have a significant time-delay built into
the controls so they do not 'hunt' or respond to short drops in voltage such
as starting a large load. 15 seconds to several minutes is typical. So
even with load-tap-changers, starting a single load that is a high
percentage of the system capacity will *still* result in a voltage dip.
daestrom
"daestrom" <daestrom@NO_SPAM_HEREtwcny.rr.com> wrote in message
news:482725ae$0$30509$4c36...@roadrunner.com...
>
<snip>
>
> But 'regulation' also is a term used to describe the inherent voltage drop
> in some devices. For example, if you review DC generators, you'll find
> that simple shunt-wound generators have fairly good 'regulation' and their
> output voltage only drops a few percent from no-load to full-load when
> supplied with a fixed field. A cumulatively-compound DC generator (which
> has a series field and a shunt field), can have a nearly flat voltage
> curve from no-load to full-load with just a fixed shunt excitation, or
> even have a voltage rise depending on the degree of compounding. (of
> course, an active voltage regulator can counteract whatever inherent
> regulation a machine may have)
>
Sorry, should be '...contribute to whatever inherent regulation a machine
may have'
daestrom
Tzortzakakis Dimitrios
? "daestrom" <daestrom@NO_SPAM_HEREtwcny.rr.com> ?????? ??? ??????
news:482725ae$0$30509$4c36...@roadrunner.com...
>
> "Tzortzakakis Dimitrios" <no...@nospam.void> wrote in message
> news:g04cc6$edo$1...@mouse.otenet.gr...
>>
>> ? "Andrew Gabriel" <and...@cucumber.demon.co.uk> ?????? ??? ??????
>> news:48246da4$0$657$5a6a...@news.aaisp.net.uk...
> <snip>
>>> The transformers are small in comparison, which gives poor
>>> regulation in comparison (and as I said before, it's the
>>> regulation at 120V which is the primary concern -- regulation
>>> of 240V across 2 hots doesn't matter much for typical US 240V
>>> loads).
>> The regulation, at least in Europe, is done at 150/15 kV substations and
>> at the HV side of the transformers, thus at 150 kV. Typical current for 2
>> x 25 MVA transformers is 150 A, 150 kV and of course secondary at 15 kV,
>> 1500 A. The regulation is done automatically with tap changers, live. The
>> local transformers at your neighborhood are fixed tap, 15 kV (they intend
>> to change everything to 20 kV).
>>
>>
>
> You're confusing two uses of the term 'regulation'. Tap changers and
> voltage regulators actively sense the terminal voltage and adjust
> 'something' to maintain the voltage within some design limit. That's a
> 'regulator' and provides 'regulation' of the sensed voltage.
>
> But 'regulation' also is a term used to describe the inherent voltage drop
> in some devices. For example, if you review DC generators, you'll find
> that simple shunt-wound generators have fairly good 'regulation' and their
> output voltage only drops a few percent from no-load to full-load when
> supplied with a fixed field. A cumulatively-compound DC generator (which
> has a series field and a shunt field), can have a nearly flat voltage
> curve from no-load to full-load with just a fixed shunt excitation, or
> even have a voltage rise depending on the degree of compounding. (of
> course, an active voltage regulator can counteract whatever inherent
> regulation a machine may have)
>
then, we would be having a power plant at each neighborhood, instead of the
300 MW ones.
> In the case of simple fixed-tap transformers, the term 'regulation' can be
> used to describe how much the output terminal voltage changes from no-load
> to full-load if the primary voltage is held constant. This use is less
> than perfect as it is much better to use the transformer's impedance along
> with the load's power factor to get a more precise answer.
>
> In the US, voltage regulation is accomplished with load-tap-changers,
> capacitor banks, and other 'voltage support services'.
substation, 15 kV line-to-line voltage.
But just like in
> Europe, it is done at the substation or higher level and not done at the
> typical distribution transformer. There are exceptions for rural areas
> though where the line length of the primary leads to some issues.
>
> daestrom
> P.S. In the US, a 'tap-changer' may be built for either for unloaded or
> loaded operation. The 'unloaded' type can not be stepped to another tap
> while there is load on the unit (although it can still be energized).
> It's switch contacts cannot interrupt load though, so if you try to move
> it while loaded, you can burn up the tap-changer. The classic
> 'load-tap-changer' is actually several switches that are controlled in a
> precise sequence to shift the load from one tap of the transformer to
> another while not interrupting the load current.
>
> P.P.S. Load tap changers typically have a significant time-delay built
> into the controls so they do not 'hunt' or respond to short drops in
> voltage such as starting a large load. 15 seconds to several minutes is
> typical. So even with load-tap-changers, starting a single load that is a
> high percentage of the system capacity will *still* result in a voltage
> dip.
>
manual control.
>
I know, I know, my answer was a bit provocative:-) And of course there are
DC regulators.... You're talking about DC generators;the one a 300 MW uses
for excitation is 220 V, 1000 A DC and probably shunt field. I have seen
here in some machine shops the old type welding generator, which is a 3
phase induction motor coupled to (usually) a compound field DC generator,
which provides the welding current. The modern ones are, maybe, not larger
than a shoe box and powered by a higher wattage 230 V 16 A receptacle.
(Usual receptacles are 230 V 10 A;16 A for washing machines, dryers and the
like).
Michael Moroney
>P.S. In the US, a 'tap-changer' may be built for either for unloaded or
>loaded operation. The 'unloaded' type can not be stepped to another tap
>while there is load on the unit (although it can still be energized). It's
>switch contacts cannot interrupt load though, so if you try to move it while
>loaded, you can burn up the tap-changer. The classic 'load-tap-changer' is
>actually several switches that are controlled in a precise sequence to shift
>the load from one tap of the transformer to another while not interrupting
>the load current.
>P.P.S. Load tap changers typically have a significant time-delay built into
>the controls so they do not 'hunt' or respond to short drops in voltage such
>as starting a large load. 15 seconds to several minutes is typical. So
>even with load-tap-changers, starting a single load that is a high
>percentage of the system capacity will *still* result in a voltage dip.
Are the load tap generators configured make-before-break?
Break-before-make would mean a (very short) power outage every activation
but make-before-break would mean a momentarily short-circuited winding and
the break would involve interrupting a large short circuit current.
Certainly modern ones likely use thyristors and zero crossing detectors.
When I was a kid living in a rather rural area, there would be a pair of
these on poles every few miles, connected open delta. (all transformer
primaries were connected phase-phase then).
phil-new...@ipal.net
| A shame that Tesla won the infamous "battle" and we don't have DC:-() But
| then, we would be having a power plant at each neighborhood, instead of the
| 300 MW ones.
And the latter make easy terrorism targets, too.
| I know, I know, my answer was a bit provocative:-) And of course there are
| DC regulators.... You're talking about DC generators;the one a 300 MW uses
| for excitation is 220 V, 1000 A DC and probably shunt field. I have seen
| here in some machine shops the old type welding generator, which is a 3
| phase induction motor coupled to (usually) a compound field DC generator,
| which provides the welding current. The modern ones are, maybe, not larger
| than a shoe box and powered by a higher wattage 230 V 16 A receptacle.
| (Usual receptacles are 230 V 10 A;16 A for washing machines, dryers and the
| like).
You don't use 400 V for anything heavy duty like an oven?
danny burstein
>In alt.engineering.electrical Tzortzakakis Dimitrios <no...@nospam.void> wrote:
>| A shame that Tesla won the infamous "battle" and we don't have DC:-() But
>| then, we would be having a power plant at each neighborhood, instead of the
>| 300 MW ones.
>And the latter make easy terrorism targets, too.
And so does that 20 gallons of gasoline parked
in front of your house. And that 500 gallons
of diesel fuel in your basment. And that 20,000
or so gallons in the nearby gas station.
Yawn.
--
_____________________________________________________
Knowledge may be power, but communications is the key
dan...@panix.com
[to foil spammers, my address has been double rot-13 encoded]
phil-new...@ipal.net
| Are the load tap generators configured make-before-break?
| Break-before-make would mean a (very short) power outage every activation
| but make-before-break would mean a momentarily short-circuited winding and
| the break would involve interrupting a large short circuit current.
I wonder how much regulation could be managed through the use of variable
leakage inductance in the transformer windings.
| Certainly modern ones likely use thyristors and zero crossing detectors.
With zero crossing detection, then the switching is not happening on all phases
at the same time.
James Sweet
phil-new...@ipal.net wrote:
> In alt.engineering.electrical Tzortzakakis Dimitrios <no...@nospam.void> wrote:
>
> | A shame that Tesla won the infamous "battle" and we don't have DC:-() But
> | then, we would be having a power plant at each neighborhood, instead of the
> | 300 MW ones.
>
> And the latter make easy terrorism targets, too.
>
>
> | I know, I know, my answer was a bit provocative:-) And of course there are
> | DC regulators.... You're talking about DC generators;the one a 300 MW uses
> | for excitation is 220 V, 1000 A DC and probably shunt field. I have seen
> | here in some machine shops the old type welding generator, which is a 3
> | phase induction motor coupled to (usually) a compound field DC generator,
> | which provides the welding current. The modern ones are, maybe, not larger
> | than a shoe box and powered by a higher wattage 230 V 16 A receptacle.
> | (Usual receptacles are 230 V 10 A;16 A for washing machines, dryers and the
> | like).
>
> You don't use 400 V for anything heavy duty like an oven?
>
In North America, 240V 50A is pretty standard for ovens, some are 40A,
clothes dryers are 30A, most other stuff plugs into a 15A 120V receptacle.
Michael Moroney
>In alt.engineering.electrical Michael Moroney <mor...@world.std.spaamtrap.com> wrote:
>| Are the load tap generators configured make-before-break?
>| Break-before-make would mean a (very short) power outage every activation
>| but make-before-break would mean a momentarily short-circuited winding and
>| the break would involve interrupting a large short circuit current.
>I wonder how much regulation could be managed through the use of variable
>leakage inductance in the transformer windings.
Good question.
>| Certainly modern ones likely use thyristors and zero crossing detectors.
>With zero crossing detection, then the switching is not happening on all phases
>at the same time.
Since the ones I've seen are 3 (or 2) independent autotransformers, this
is true without zero crossing detectors, and the power supplied may not
always be of equal voltages 120 degrees apart.
daestrom
"Michael Moroney" <mor...@world.std.spaamtrap.com> wrote in message
news:g0a1o5$bcq$1...@pcls6.std.com...
I figured someone would 'bite' :-)
Typical large power load-tap-changers have a primary winding and two
secondaries. One secondary produces about 100% of 'rated' secondary
voltage. The second secondary produces about 15% to 20% of the rated
voltage, but has numerous taps from end to end, about 2.5% 'steps'. (for a
total of about eight taps). The cental tap of the boost/buck winding is
tied to one end of the main secondary. The boost/buck can be used to step
from 90% to 110% of the 'design' output. I suppose some can step over a
wider range, but I haven't run across them.
*TWO* rotary switches have each tap tied to one of the positions of each
rotory switch, and each 'wiper' is tied to single heavier contacts that are
opened in the operating sequence. The output side of these two interrupting
contacts are tied to each end of a large center-tapped inductor.
So, normally both rotary switches are aligned to the same transformer tap,
both interrupting contacts are shut, and load current flows from the
boost/buck winding tap, splits and flows through both rotary switches, both
interrupting contacts, enters both ends of the inductor and out the inductor
center tap. Because the current flows into both ends of the inductor and
the mutual inductance of the two parts cancel, there is little voltage drop
in the inductor.
Begin step sequence:
1) Open one interrupting contactor. Now load current doubles through half
the inductor and is zero in the other half, so the voltage drop across the
inductor actually makes output voltage drop, even if trying to step 'up'.
2) Move associated rotary switch to next step of transformer bank.
3) Close interrupting contactor. Now, the two rotary switches are across
different taps. The inductor prevents a excessive current, otherwise you
have a direct short of the two winding taps. Some tap changers can stop at
this point and are called 'half-step' units. Obviously, the inductor has to
be rated for sustained operation across a step of the boost/buck winding
plus load current in order to survive sustained 'half step' operation.
4) But for tap changers that can't operate 'half-step', the sequence
continues. And opens the other interrupting contactor. Now the other half
of the inductor has full load current.
5) Move second rotary switch to next step (now both switches are on the new
step)
6) Close the second interrupting contactor. You're back in the initial
configuration, but with both rotary switches on a new transformer tap.
Older units do this whole thing with a fancy cam/gear arrangement circa
1940's. Just takes a single reversable motor to drive the unit and some
limit switches to be sure it can only stop at full 'steps' (or 'half steps'
for those capable of running 'half-step')
Because the system intermittently inserts an additional voltage drop through
the inductor, the control circuits typically have time-delays that prevent
it trying to reverse direction or something while stepping.
As far as zero-crossing and thyristors, I suppose it's certainly possible,
but I haven't run across them for large substations. I have seen such a
setup in power-conditioners for computer complexes and such, but that's only
a few kVA (one unit I know of was rated for 25 kVA).
The mechanical-switch tap changer is well-matured and has the nice advantage
that when they 'fail', they 'fail' at the last 'step' and power continues to
flow (albeit perhaps the wrong voltage).
> When I was a kid living in a rather rural area, there would be a pair of
> these on poles every few miles, connected open delta. (all transformer
> primaries were connected phase-phase then).
Those are smaller than the units I'm thinking of. I'm talking about
multiple MVA rated units.
daestrom
daestrom
<phil-new...@ipal.net> wrote in message
news:g0a7t...@news5.newsguy.com...
> In alt.engineering.electrical Michael Moroney
> <mor...@world.std.spaamtrap.com> wrote:
>
> | Are the load tap generators configured make-before-break?
> | Break-before-make would mean a (very short) power outage every
> activation
> | but make-before-break would mean a momentarily short-circuited winding
> and
> | the break would involve interrupting a large short circuit current.
>
> I wonder how much regulation could be managed through the use of variable
> leakage inductance in the transformer windings.
>
I suppose you could, but increasing leakage inductance means you're
increasing losses aren't you? Just a percent or two on a unit rated for 250
MVA can be too much to tolerate.
daestrom
daestrom
"Tzortzakakis Dimitrios" <no...@nospam.void> wrote in message
>
> ? "daestrom" <daestrom@NO_SPAM_HEREtwcny.rr.com> ?????? ??? ??????
> news:482725ae$0$30509$4c36...@roadrunner.com...
Thing about DC generators used for welding, they are often *differentially*
compounded, whereas those used for conventional power production are
*cummulatively* compounded.
For power production, the series winding is arranged so that additional load
will add MMF to the shunt field and help to compensate for the various
internal factors causing a voltage drop.
But for welding, you don't want a constant voltage so much as a constant
current. By using a differentially connected series winding, any increase
in current in the series winding opposes the shunt winding, rapidly dropping
the terminal voltage. So with no arc, the shunt winding gives you a nice,
fairly high voltage to strike an arc, and as soon as you do, the voltage
drops to whatever level is needed to maintain a specific current. Tap
settings allow the welder to adjust what amount of current he gets so he can
adjust for different welding. Often the 'course' adjustments are done with
different taps to the series winding, and a final 'fine' adjustment is done
with a lower-wattage rheostat controlling the exact amount of shunt-field
current.
DC machines are often under-appreciated :-)
(not to mention that some of this technology is older than either one of us
and probably older than both of us put together)
daestrom
Andrew Gabriel
Some parts of Europe do. You find ovens can be strapped to
run from one or two phases, depending what's available on
the premises. Some parts of Europe use 3-phase 400V domestic
water heaters.
maa...@panic.xx.tudelft.nl
> I'm a little confused about a 230 volt circuit. In what part of the
> world does the utility supply 230v?
Continental Europe used to have 220 volts (before that it was 127 volts in
some places), the UK used to have 240 volts. Nowadays, the common voltage
is 230 volts -10% +6%.
--
Met vriendelijke groet,
Maarten Bakker.
ItWasAnInsideJob
>> And the latter make easy terrorism targets, too.
>
> And so does that 20 gallons of gasoline parked
> in front of your house. And that 500 gallons
> of diesel fuel in your basment. And that 20,000
> or so gallons in the nearby gas station.
>
> Yawn.
>
Michael A. Terrell
maa...@panic.xx.tudelft.nl wrote:
>
> In sci.electronics.repair jakdedert <jakd...@bellsouth.net> wrote:
> > I'm a little confused about a 230 volt circuit. In what part of the
> > world does the utility supply 230v?
>
> Continental Europe used to have 220 volts (before that it was 127 volts in
> some places), the UK used to have 240 volts. Nowadays, the common voltage
> is 230 volts -10% +6%.
In other words, nothing has changed. They just wrote sloppier specs.
phil-new...@ipal.net
But we don't have an easy option for any higher voltage. In many parts of
Europe, three phase 400/230V is delivered to homes. Then using 400V, either
2 lines or all 3 lines, is an option.
phil-new...@ipal.net
Isn't it just inductance in series? Shouldn't that just be a phase shift as
seen from the primary side?
Don Kelly
----------------------------
"Michael Moroney" <mor...@world.std.spaamtrap.com> wrote in message
news:g0a1o5$bcq$1...@pcls6.std.com...
> "daestrom" <daestrom@NO_SPAM_HEREtwcny.rr.com> writes:
>
>
>>P.S. In the US, a 'tap-changer' may be built for either for unloaded or
>>loaded operation. The 'unloaded' type can not be stepped to another tap
>>while there is load on the unit (although it can still be energized).
>>It's
>>switch contacts cannot interrupt load though, so if you try to move it
>>while
>>loaded, you can burn up the tap-changer. The classic 'load-tap-changer'
>>is
>>actually several switches that are controlled in a precise sequence to
>>shift
>>the load from one tap of the transformer to another while not interrupting
>>the load current.
>
>>P.P.S. Load tap changers typically have a significant time-delay built
>>into
>>the controls so they do not 'hunt' or respond to short drops in voltage
>>such
>>as starting a large load. 15 seconds to several minutes is typical. So
>>even with load-tap-changers, starting a single load that is a high
>>percentage of the system capacity will *still* result in a voltage dip.
>
> Are the load tap generators configured make-before-break?
> Break-before-make would mean a (very short) power outage every activation
> but make-before-break would mean a momentarily short-circuited winding and
> the break would involve interrupting a large short circuit current.
--------
Yes -you are shorting a part of the winding but the switching is a bit more
complex than that so that short circuit currents are limited to reasonable
values. It is a multistep operation with reactor switching. On-load tap
changers are expensive and are generally limited to applications where this
is absolutely needed (I have seen one where the tap changer was nearly as
large as the transformer).
--------------
>
> Certainly modern ones likely use thyristors and zero crossing detectors.
-------------
Possibly but probably not- I am out of date on this but I would expect that
the old way of good switches plus reactors might still be the better way. It
saves a lot of control wiring plus a lot of money to operate thyristors at
300KV and 500A or more and I doubt whether they would be cost effective or
technically advantageous otherwise. --------------------------
>
> When I was a kid living in a rather rural area, there would be a pair of
> these on poles every few miles, connected open delta. (all transformer
> primaries were connected phase-phase then).
"on load tap changers"? Not likely. These were applied to transformers only
where it was worth the effort.
Definitely transformers in rural areas- typical pole pigs- would have to be
de-energized as the tap changer is a manually operated switch inside the
tank. Some larger transformers did have off-load but live changers operated
from ground level. What you saw could have been somethng else altogether.
Delta primaries as you indicate were around when you were a kid, would, in
most areas mean that you are now a pensioner. I remember cases of conversion
from delta to star for distribution primaries in small towns being done
about 60 years ago and use of delta for transmission died much before that.
--
Don Kelly dh...@shawcross.ca
remove the X to answer
Don Kelly
I don't see changing leakage inductance having much effect on losses ( a
great effect on voltage regulation -likely all to the bad) but the problem
is one of changing leakage inductance.
Does this mean changing a gap in the core? Does it mean moving one winding
with respect to another? In any case it does mean some fiddling with the
core or winding.
This has been done for series lighting circuits where the load current was
kept constant by using a transformer which balanced the forces between coils
against a fixed weight. If the current changed the secondary coil moved so
that there was more or less leakage. The units that I have seen were rather
cumbersome.
Thomas Tornblom
> maa...@panic.xx.tudelft.nl wrote:
>>
>> In sci.electronics.repair jakdedert <jakd...@bellsouth.net> wrote:
>> > I'm a little confused about a 230 volt circuit. In what part of the
>> > world does the utility supply 230v?
>>
>> Continental Europe used to have 220 volts (before that it was 127 volts in
>> some places), the UK used to have 240 volts. Nowadays, the common voltage
>> is 230 volts -10% +6%.
>
>
> In other words, nothing has changed. They just wrote sloppier specs.
It has changed, the voltage is now close to 230V, at least in Sweden.
I guess the sloppiness was specified to allow a gradual switch from
220/240 to 230 and still be within spec.
Residential power in Norway is normally 230V three phase btw, instead
of 400V three phase. Their 230V outlets are two phase and ground
instead of one phase, neutral and ground. Their three phase outlets
therefore are blue instead of red and have four prongs instead of five.
Michael A. Terrell
Do the math. The specifications allow continued use of the old
standard n each country.
Thomas Tornblom
> Thomas Tornblom wrote:
>>
>> "Michael A. Terrell" <mike.t...@earthlink.net> writes:
>>
>> > maa...@panic.xx.tudelft.nl wrote:
>> >>
>> >> In sci.electronics.repair jakdedert <jakd...@bellsouth.net> wrote:
>> >> > I'm a little confused about a 230 volt circuit. In what part of the
>> >> > world does the utility supply 230v?
>> >>
>> >> Continental Europe used to have 220 volts (before that it was 127 volts in
>> >> some places), the UK used to have 240 volts. Nowadays, the common voltage
>> >> is 230 volts -10% +6%.
>> >
>> >
>> > In other words, nothing has changed. They just wrote sloppier specs.
>>
>> It has changed, the voltage is now close to 230V, at least in Sweden.
>>
>> I guess the sloppiness was specified to allow a gradual switch from
>> 220/240 to 230 and still be within spec.
>>
> Do the math. The specifications allow continued use of the old
> standard n each country.
If you read my comment you will see that I agree that the new spec
covers the old voltages. I do not agree with your statement that
"nothing has changed". We had 220V before and we now have 230V, so the
actual voltage has definitely changed.
Ian Jackson
writes
In the UK, we had 240V. We now have err..... 240V.
There may be places where it really has been reduced to 230V, but I've
never been anywhere where I had occasion to measure the mains voltage,
and didn't get around 240V - certainly not sufficiently different for
you to notice the difference.
--
Ian
Tzortzakakis Dimitrios
300 MW unit is powered directly from the turbo alternator (21 kV) and has a
secondary of 6.6 kV and a tetriary of again 6.6 kV. This is done because it
has wye-wye-wye connection (IIRC). The hotel load of such a unit is 10%,
also 30 MW, including 7 brown coal mills. Typical size of a 6.6 kV motor is
1 MW.
diesel-electric transmission, and also in pure electric locomotives (E-Lok
in german, for Elektrische Lokomotive). The diesel engine, 2-stroke and
usually 600 to 900 rpm at full throttle, is coupled to a generator. The
generator has small windings, connected in series for the last notch, higher
voltage and relatively smaller current, and in parallel for start, higher
amperage and smaller voltage. The traction motors are directly coupled on
the wheel shaft, and are air cooled. An E-Lok has a trasformer, with the
primary directly supplied by the cetenary, 15 kV 16 2/3 Hz in Germany, and
25 kV 50 Hz in Greece, The secondary uses the same principle. The typical
size of a traction motor is 1 MW, 4 (one each shaft) and maximum voltage 700
volts, and are series wound motors with special construction to operate at
16 2/3 Hz (or 50 Hz with today's technology). Typical power of a diesel
locomotive is 2850 HP, while an electric is 6000 HP. with 1500 HP at each
shaft, also ~1MW. There is a heavy duty 12,000 HP diesel engine in USA(with
6 shafts, also 2000 HP at each shaft). The high speed ICE train
(InterCityExpress) in germany is 13,000 HP, has a normal travelling speed of
200 km/h, 2 locomotives, 3-phase induction motors, electronic drive.
> Older units do this whole thing with a fancy cam/gear arrangement circa
> 1940's. Just takes a single reversable motor to drive the unit and some
> limit switches to be sure it can only stop at full 'steps' (or 'half
> steps' for those capable of running 'half-step')
>
> Because the system intermittently inserts an additional voltage drop
> through the inductor, the control circuits typically have time-delays that
> prevent it trying to reverse direction or something while stepping.
>
> As far as zero-crossing and thyristors, I suppose it's certainly possible,
> but I haven't run across them for large substations. I have seen such a
> setup in power-conditioners for computer complexes and such, but that's
> only a few kVA (one unit I know of was rated for 25 kVA).
>
> The mechanical-switch tap changer is well-matured and has the nice
> advantage that when they 'fail', they 'fail' at the last 'step' and power
> continues to flow (albeit perhaps the wrong voltage).
>
>> When I was a kid living in a rather rural area, there would be a pair of
>> these on poles every few miles, connected open delta. (all transformer
>> primaries were connected phase-phase then).
>
> Those are smaller than the units I'm thinking of. I'm talking about
> multiple MVA rated units.
>
--
Tzortzakakis Dimitrios
major in electrical engineering
mechanized infantry reservist
hordad AT otenet DOT gr
NB:I killfile googlegroups.
Tzortzakakis Dimitrios
Ο <phil-new...@ipal.net> έγραψε στο μήνυμα
news:g0a7l...@news5.newsguy.com...
> In alt.engineering.electrical Tzortzakakis Dimitrios <no...@nospam.void>
> wrote:
>
> | A shame that Tesla won the infamous "battle" and we don't have DC:-()
> But
> | then, we would be having a power plant at each neighborhood, instead of
> the
> | 300 MW ones.
>
> And the latter make easy terrorism targets, too.
>
>
> | I know, I know, my answer was a bit provocative:-) And of course there
> are
> | DC regulators.... You're talking about DC generators;the one a 300 MW
> uses
> | for excitation is 220 V, 1000 A DC and probably shunt field. I have seen
> | here in some machine shops the old type welding generator, which is a 3
> | phase induction motor coupled to (usually) a compound field DC
> generator,
> | which provides the welding current. The modern ones are, maybe, not
> larger
> | than a shoe box and powered by a higher wattage 230 V 16 A receptacle.
> | (Usual receptacles are 230 V 10 A;16 A for washing machines, dryers and
> the
> | like).
>
> You don't use 400 V for anything heavy duty like an oven?
>
earth, goes without saying). Just if you connect it on 1 phase (as usually)
you use a bridge, and connect all L1-L2-L3 to the one and only hot. 230 V is
powerful enough for almost everything in a house, only large airconditioners
are 3 phase, and all industrial motors, even if they are 1HP:-) (
> --
--
Tzortzakakis Dimitrios
major in electrical engineering
mechanized infantry reservist
hordad AT otenet DOT gr
NB:I killfile googlegroups.
Michael Moroney
>"Michael Moroney" <mor...@world.std.spaamtrap.com> wrote in message
>news:g0a1o5$bcq$1...@pcls6.std.com...
>>
>> Are the load tap generators configured make-before-break?
>> Break-before-make would mean a (very short) power outage every activation
>> but make-before-break would mean a momentarily short-circuited winding and
>> the break would involve interrupting a large short circuit current.
>--------
>Yes -you are shorting a part of the winding but the switching is a bit more
>complex than that so that short circuit currents are limited to reasonable
>values. It is a multistep operation with reactor switching. ...
Thanks for your (and esp. daestrom's) explanation on how they work.
>> When I was a kid living in a rather rural area, there would be a pair of
>> these on poles every few miles, connected open delta. (all transformer
>> primaries were connected phase-phase then).
>"on load tap changers"? Not likely. These were applied to transformers only
>where it was worth the effort.
>Definitely transformers in rural areas- typical pole pigs- would have to be
>de-energized as the tap changer is a manually operated switch inside the
>tank. Some larger transformers did have off-load but live changers operated
>from ground level. What you saw could have been somethng else altogether.
I'm not completely sure what these are other than being told that they
were voltage regulators (tapped autotransformers) long ago. These are
large cans with 3 bushings on top, taller and slimmer than most pole pigs,
and they usually have a control box on the pole around eye level. I see
the same style cans in substations between the stepdown transformer and
the distribution system except they sit on the ground and come in sets of
three.
>Delta primaries as you indicate were around when you were a kid, would, in
>most areas mean that you are now a pensioner. I remember cases of conversion
>from delta to star for distribution primaries in small towns being done
>about 60 years ago and use of delta for transmission died much before that.
While I'm hardly a kid, I'm no pensioner yet. In fact my father's place
still has delta-connected distribution primaries in the area, at 7200
volts (I have an old fuse/switch holder from there labelled 7200V ??A).
Where I mentioned they had pairs of these "voltage regulators" (or
whatever they were) every several miles was a long run along a state
highway. At some point they upgraded it to a wye configuration, probably
at a higher voltage. However, several side branches haven't been upgraded
yet. On the side branch feeding my father's place there is a bank of 3
transformers connected wye-delta immediately followed by a pair of these
"voltage regulator" cans connected open delta. From that point on the
distribution system is visibly old.
daestrom
"Don Kelly" <dh...@shaw.ca> wrote in message
news:%K9Wj.264923$pM4.64562@pd7urf1no...
Yep. Seen those types of units and was about to mention them. One model
had a core that had a space in it much like a D'Arsonval meter movement.
The space was filled with a 'bobbin' that when cross-ways left two large
air-gaps and when aligned would neatly bring the gap between the two sides
of the core. A weight and lever would turn the 'bobbin' into/outof the core
to control the current.
Problem with those is, if you get a loose connection or arc, the unit will
just keep pumping power to the system no matter what.
daestrom
James Sweet
>
> Yep. Seen those types of units and was about to mention them. One
> model had a core that had a space in it much like a D'Arsonval meter
> movement. The space was filled with a 'bobbin' that when cross-ways left
> two large air-gaps and when aligned would neatly bring the gap between
> the two sides of the core. A weight and lever would turn the 'bobbin'
> into/outof the core to control the current.
>
> Problem with those is, if you get a loose connection or arc, the unit
> will just keep pumping power to the system no matter what.
>
> daestrom
>
The only place I've seen those used was for regulating current in 6.6A
(usually) series loop streetlighting. Lots of this still left in the Los
Angeles area and a few other pockets but most is gone by now. It was
very common from the 20s up through the 60s though, incandescent at
first, but 6.6A matching transformer "ballasts" are available for HID
lamps as well. Most airfield illumination is still 6.6A series, I
suspect the modern control gear is solid state.
Westinghouse had a design where the secondary was on a linear mechanism
with a counterweight and would float above the primary. Current was
adjusted by moving the counterweight.
daestrom
"Tzortzakakis Dimitrios" <no...@nospam.void> wrote in message
In US, diesel-electric used to always be DC machines, but modern ones are
now AC generators with thyristers to regulate the power flow to the traction
motors. Traction motors are still DC however to allow for their use in
dynamic braking.
I suppose in Europe the better way to go would be regenerative braking,
putting the braking power back into the overhead line, but that would need a
static inverter. Probably the transformer secondary has a four-quadrant
converter to allow reversal of power flow ??
Nice thing about the newer solid-state control systems (AC-Generator/
DC-Traction) is the ability to control wheel-slip. In the old days it took
a skilled engineer (the train-driving kind) to get maximum power without
slipping a lot (and wasting a lot of sand). Now modern units have speed
sensors on each individual wheel set and control the power flow to
individual traction motors. As soon as a wheel set starts to slip it can
redirect power flow to other traction motors to prevent the slipping set
from 'polishing the rail'. This prolongs life of the wheels and rail and
actually improves the maximum tractive effort a locomotive can deliver. And
when hauling 100+ cars of coal in a unit train up grade, tractive effort is
what keeps you moving.
You forgot to mention that traction motors often have separately powered
blower motors for air-cooling. This is because the motor may spend hours
operating at low speeds and shaft-mounted cooling fans are not enough. The
motor blower is usually mounted up inside the engine house and connects to
the traction motor via a large flexible duct.
Some diesel-electric unitl have six axles and six traction motors. The
trade-off is between how much power you can get to the traction motors and
how much weight you can keep on the wheels to keep them from slipping. Sand
is okay for starting and some special situations, but you can't carry enough
to use it for an entire run. But of course too much weight and you need
more axles to protect the rail from damage (depending on the size of the
rail being used).
daestrom
P.S. As you can see, I've seen a few railroad locomotives as well. Mostly
just the older EMD's though, not GE's newer 'green' units.
phil-new...@ipal.net
|
|> In alt.engineering.electrical Tzortzakakis Dimitrios <no...@nospam.void>
|> wrote:
|>
|> | A shame that Tesla won the infamous "battle" and we don't have DC:-()
|> But
|> | then, we would be having a power plant at each neighborhood, instead of
|> the
|> | 300 MW ones.
|>
|> And the latter make easy terrorism targets, too.
|>
| I cross my fingers that terrorists get no electrical engineering degree:0
I suspect quite many already have them. Many have degrees in a lot of other
things like chemistry and physics. Some even have doctoral level degrees.
|> | I know, I know, my answer was a bit provocative:-) And of course there
|> are
|> | DC regulators.... You're talking about DC generators;the one a 300 MW
|> uses
|> | for excitation is 220 V, 1000 A DC and probably shunt field. I have seen
|> | here in some machine shops the old type welding generator, which is a 3
|> | phase induction motor coupled to (usually) a compound field DC
|> generator,
|> | which provides the welding current. The modern ones are, maybe, not
|> larger
|> | than a shoe box and powered by a higher wattage 230 V 16 A receptacle.
|> | (Usual receptacles are 230 V 10 A;16 A for washing machines, dryers and
|> the
|> | like).
|>
|> You don't use 400 V for anything heavy duty like an oven?
|>
| Yep. All ovens sold in EU are wired for 3 phase, 400 V with neutral (and
| earth, goes without saying). Just if you connect it on 1 phase (as usually)
| you use a bridge, and connect all L1-L2-L3 to the one and only hot. 230 V is
| powerful enough for almost everything in a house, only large airconditioners
| are 3 phase, and all industrial motors, even if they are 1HP:-) (
That means each element individually runs on 230 V and they just divided them
up in three approximately equal sections, or use triple elements for each type
of use.
How many things that have just ONE (large) element would have it available in
both 230 V and 400 V versions?
phil-new...@ipal.net
The thought is to change the core in some way. Maybe that can be done in a
gradual way, as opposed to winding taps that have to be either BtM or MtB.
| This has been done for series lighting circuits where the load current was
| kept constant by using a transformer which balanced the forces between coils
| against a fixed weight. If the current changed the secondary coil moved so
| that there was more or less leakage. The units that I have seen were rather
| cumbersome.
I'm thinking more along the lines of a motor drive to move the coil, and
that be controlled by the same authority that would have controlled the
steppable taps.
phil-new...@ipal.net
| Yes -you are shorting a part of the winding but the switching is a bit more
| complex than that so that short circuit currents are limited to reasonable
| values. It is a multistep operation with reactor switching. On-load tap
| changers are expensive and are generally limited to applications where this
| is absolutely needed (I have seen one where the tap changer was nearly as
| large as the transformer).
I was thinking of what I might do to get some fine voltage control within a
very limited range around 120 volts. The obvious option was a 0-140 volt
variable transformer. But I wanted to make sure I had a setup that could
be better limited, for example, to not allow an accidental too low voltage.
I also didn't want to run all the power through the variable. So what I
was going to do was get a smaller variable transformer, and two buck-boost
transformers. One transformer would be wired 120->16 in buck mode to drop
the voltage down to 104. The other transformer would be wired 120->24 and
supplied via the 0-140 variable transformer, giving me a 0-28 variable boost.
The end result is 104-132 over the full range of variable transformer control
(assuming the boost transformer has no issues with being overfed at 140V).
So I might envision a transformer where the taps can be part of a boost
transformer added to the main transformer. The first buck transformer in
my above example would not be needed because the main transformer would be
designed with a 1st secondary at the lowest voltage of the adjustable range.
A 2nd secondary on the same main transformer would have the adjustable taps
and it would feed a separate boost transformer which has a secondary wired
in series with the 1st secondary of the main. So the taps would only be
dealing directly with a fraction of the power (assuming there is no back
feed issue involved) based on the needed adjustment range.