Connect with us

Closed Delta 120/240V 3-phase service

Discussion in 'Electrical Engineering' started by Beachcomber, Feb 10, 2008.

Scroll to continue with content
  1. krw

    krw Guest

    Either that or CT secondaries. Same difference.
    IF there is any advantage (doubt it), they'll figure out how to wire
    it up. It's rather obvious.
    Yes, that's why I see nothing unique about your "idea". It's done
    today, except there is no need for the inversion.
    There is likely a reason they don't. Though in your case of an
    apartment building they do, though likely with individual
    transformers. It's done on 90% of the poles in the country.
    No different than what happens on 90% of the poles in the country,
    except those are in three cans rather than one.
    A distinction without a difference. WHo cares how many screws are
    on the terminal board?
    Sure. If there is no reason to make a widget there is a good chance
    that most are unfamiliar with the widget.
    "Wye" is usually in quotes, even in a normal implementation.
    Certainly it is, on 90% of the poles in the country.
    The CT on any leg.
    It's a "wye" not a delta. Three transformers with CT secondaries
    from A-N, B-N, and C-N. You just made you "star" configuration.
    I didn't say an individual home was getting three phase, but it's
    there on the pole. ...including your "star".

    Look at 100 random poles. You'll see 90 of them wired as 3-phase
    "wye" (really doesn't matter if they are delta). The secondaries
    are CTed, so you have the six points of your "star". Nothing new
    here.
    You've seen it, just haven't called it that. There is no point to
    it, so it isn't named.
    Irrelevant manufacturing detail.
     
  2. krw

    krw Guest

    ....and the house to the north gets:

    * *
    \ /
    *--*
    \
    *

    ....and the house to the south gets:


    *
    /
    *--*
    / \
    * *

    And pretty soon you have something on the pole that looks kinda
    like:

    * *
    \ /
    *--*--*
    / \
    * *
    Three phase also sorta allows them to deliver more power for a given
    conductor size.
     
  3. Guest

    | In article <>, phil-news-
    | says...
    |> | In article <>, phil-news-
    |> | says...
    |> |> | In article <>, phil-news-
    |> |
    |> | <attempt to snip to size>
    | <more>
    |> |> That is the same as the six-phase "star" or "6 star". So if you can't
    |> |> see any difference, that's because there isn't any. I would not have
    |> |> called this a "wye" of any sort since it doesn't look like a "Y". But
    |> |> it could be TWO Y's interleaved.
    |> |
    |> | No, not "interleaved" but split. Invert each phase, as in a center-
    |> | tapped transformer (I.e. split) and you're there.
    |>
    |> You mean like having 2 three phase 208Y/120 transformers, one fed 180 degrees
    |> out of phase from the other, and combining their outputs with neutrals tied
    |> together? That's what I meant by interleaved. If that's not what you are
    |> saying, then I don't understand what it is you are saying.
    |
    | Either that or CT secondaries. Same difference.
    |
    |> |> To make this derived system, you need either:
    |> |>
    |> |> 1. 3 single phase transformer cores
    |> |
    |> | Kinda like they do now on the pole.
    |>
    |> Yes. Except instead of using 120-volt-only transformers (there are such
    |> things ... just 2 lugs on the secondary), they need to use the 120/240 volt
    |> transformers (plenty of those around) and understand the concept to know
    |> how to wire it up.
    |
    | IF there is any advantage (doubt it), they'll figure out how to wire
    | it up. It's rather obvious.

    There is an advantage to having genuine 240 volts. Not all circumstances
    make it easy to use separate single phase transformers. The ones that do
    would already have multiple transformers. Otherwise it increases cost.
    And there are no "6 star" transformers made (yet).


    |> Metering that could be an issue. In the case of the apartment building,
    |> individual tenants would be metered at 120/240 so it's not an issue. But
    |> if this needs to be metered in its "6 star" configuration, it can be done
    |> with 3 CTs, each carrying the 180-degree-opposite conductor pairs running
    |> in opposing directions just as a single CT would be used for single phase
    |> power.
    |
    | Yes, that's why I see nothing unique about your "idea". It's done
    | today, except there is no need for the inversion.

    Maybe there is a confusion here. CT could mean "center tap" or it could
    mean "current transformer". In the above, I mean "current transformer"
    for the purpose of metering.


    |> |> 2. 1 three phase tranformer E-core
    |> |
    |> | Kinda...
    |>
    |> It could be done. The manufacturing just has to provide a pair of 120
    |> volt windings, or a series 120/240 tapped winding, and sufficient terminal
    |> board space to deal with it.
    |
    | There is likely a reason they don't. Though in your case of an
    | apartment building they do, though likely with individual
    | transformers. It's done on 90% of the poles in the country.

    What is done in on 90% of the poles? The "6 star" suggest is certainly not.


    |> |> Then you need to wrap these cores with 3 primary windings and 3 secondary
    |> |> windings. Usually the secondaries go on the inside and the primaries go
    |> |> on the outside, so the secondary at lower voltage and higher current has
    |> |> less winding resistance.
    |> |
    |> | Ok, I'm confused. This is different how?
    |>
    |> The difference is that a traditional E-core 208Y/120 transformer would have
    |> only ONE 120 volt winding per core bar (times the 3 core bars). Two such
    |> windings at 120 volt each, or a 120/240 volt series winding (connected in
    |> series inside the winding instead of at the terminal board) would be needed
    |> for the "6 star" configuration.
    |
    | No different than what happens on 90% of the poles in the country,
    | except those are in three cans rather than one.

    The "6 star" is not done anywhere I have ever heard of. You must be
    referring to a common WYE, which is not the same thing (WYE is a "3 star"
    not a "6 star").


    |> |> Each of the 3 secondary windings needs to be either:
    |> |>
    |> |> 1. a pair of 120 volt windings which you can wire in series
    |> |> 2. a single 240 volt winding with a center tap right in the middle
    |> |
    |> | Exactly (is there a difference?).
    |>
    |> Yes, there is a difference. In #1 you have 4 wires coming from the secondary
    |> winding to the terminal board. In #2 you have 3 such wires because the
    |> winding is series connected, possibly a continuous single wire, inside the
    |> winding itself, and just tapped at a mid-point.
    |
    | A distinction without a difference. WHo cares how many screws are
    | on the terminal board?

    You need more screws for the extra wires. How many depends on if
    you want to double up on a single lug or not.


    |> It's a difference in construction. Some people might be more familiar with
    |> one over the other.
    |
    | Sure. If there is no reason to make a widget there is a good chance
    | that most are unfamiliar with the widget.
    |
    |> |> All of the center points of these windings are wired/bonded together and
    |> |> grounded. Then each of the three phases will have two poles 180 degrees
    |> |> apart. Some people will call this six phases.
    |> |
    |> | Right; split-phase "wye".
    |>
    |> Keep the "wye" in quotes, then; it's not really wye. I would never call it
    |> a wye at all. It's a 6 pointed radial star.
    |
    | "Wye" is usually in quotes, even in a normal implementation.

    Really? I see it more NOT in quotes. The term WYE is a longish form
    of "Y" which is a depiction of a 3 pointed star configuration, not 6.
    The "*" more resembles 6 under most fonts (some have 8, but that's
    another issue).


    |> |> Which connection pair do you need to ask about?
    |> |
    |> | I don't. You seem to see a difference between this "star" and an
    |> | ordinary 3-phase "wye" that delivers residential 240V split-phase.
    |> | I don't see anything new or particularly interesting here, but am
    |> | trying.
    |>
    |> A true WYE is not split phase. That makes a contradiction of terms.
    |> But if you know of a manufacturer that makes such a transformer AND
    |> calls it "split phase wye" or some such thing, please do point to
    |> their catalog reference. I've looked at a lot of transformer catalog
    |> info online and have never seen such a thing in a single transformer.
    |
    | Certainly it is, on 90% of the poles in the country.

    Since well more than 10% of poles have a traditional 3 pole wye, there
    cannot be 90% with a 6 pole three phase star arrangement.


    |> |> Between A and B you have 208 volts.
    |> |> Between B and C you have 208 volts.
    |> |> Between C and A you have 208 volts.
    |> |> Between A and N you have 120 volts.
    |> |> Between B and N you have 120 volts.
    |> |> Between C and N you have 120 volts.
    |> |>
    |> |> There aren't any other ways to connect, and no way to get 240 volts.
    |> |
    |> | That's funny, because that's exactly how I get the 240V for my house
    |> | off the 3-phases on the pole.
    |>
    |> Which connections give you 240 volts?
    |
    | The CT on any leg.

    Be specific. First of all you know you need TWO connection points for
    a voltage. Simply saying "CT" (which I assume to mean "center tap"
    instead of "current transformer") means ONE connection. You get no
    voltage from one connection.

    So how do you get 240 volts from a 208Y/120 wired transformer bank?
    Answer: you don't.


    |> If you are getting 240 volts from
    |> A-B or from B-C or from C-A, and if the phase angles really are 120 degrees
    |> as a true three phase WYE would be, then you are going to get 139 volts
    |> at A-N, B-N, and C-N. I don't think that is what you want.
    |
    | It's a "wye" not a delta. Three transformers with CT secondaries
    | from A-N, B-N, and C-N. You just made you "star" configuration.

    What are you labeling A-N, B-N, and C-N? The primaries or secondaries?
    Your statement "CT secondaries from A-N, B-N, and C-N" makes no sense.
    If there were 3 split-phase secondaries involved, there would be a lot
    more connection points than just these three. Even if all the center
    taps were connected together, you would still have 6 connection points
    to label. Starting at A, that runs to F.


    |> FYI, I did find one utility offering 240Y/139 service for some portions
    |> of their service area, as a replacement for 240D.
    |>
    |> Maybe you are getting ONE phase of 120/240 via ONE split phase transformer
    |> tapped to ONE phase (connected L-N) or TWO phases (connected L-L) of the
    |> primary distribution lines. But just because there is three phase on the
    |> distribution does NOT mean you are getting it. You are most likely getting
    |> one of: 208Y/120 three phase (my grandfather actually did get this at his
    |> home), or 120/240 single phase, or that old 240DCT/120 setup.
    |
    | I didn't say an individual home was getting three phase, but it's
    | there on the pole. ...including your "star".

    It's not there if what's on the pole is 208Y/120, which most poles
    supplying three phase power have. The only voltages available are
    208 volts and 120 volts. Every possible pairing of 2 connections
    on these very common setups gives either 208 volts or 120 volts.
    I listed them previously. I left none out. None have 240 volts.


    | <snip>
    |
    |> |>
    |> |> OK, hope the above helps.
    |> |
    |> | Nope. I'm still wondering why you see your "star" as any different
    |> | than what we see on 90% of the poles in the country.
    |>
    |> 208Y/120 is _very_ different. 208Y/120 has THREE line wires coming out at
    |> 120 degree phase angle equal intervals. The "6 star" (maybe we can call
    |> it 240*/208/120) has SIX line wires coming out at 60 degree phase angle
    |> equal intervals.
    |
    |> If I provide you with exactly 3 transformers which are wired up with one
    |> winding for the primary voltage and one winding for the secondary at 120
    |> volts, it can be wired up by connecting the primaries in whatever they
    |> need for the type of service (delta or wye) and connecting the secondaries
    |> in a wye configuration. There, you have 208Y/120 just like 90% of the
    |> three phase poles in the country (I'll just accept your stats of 90% as I
    |> do not know the actual figures).
    |
    | Look at 100 random poles. You'll see 90 of them wired as 3-phase
    | "wye" (really doesn't matter if they are delta). The secondaries
    | are CTed, so you have the six points of your "star". Nothing new
    | here.

    You really think that?

    Sure, a 120/240 volt split phase transformer used normally for single
    phase service could be used for 208Y/120 by connecting only ONE SIDE.
    And it might be done in a few places. But it would be very rare since
    it is a waste of half the transformer capacity, and thus a higher cost
    than needed. They do make transformers that can deliver their entire
    capacity on just 2 lugs at 120 volts. There is no center tap. Or if
    there is, the center of 120 is 60 so it would not be used.

    The majority of 208Y/120 services derived using single phase pole pigs
    is done with 3 cans that have 120 volt ONLY secondaries.


    |> I have never seen, and never heard of, any "6 star" or 240*/208/120 setup
    |> anywhere. I have never seen any utility tariff (I've looked through a few
    |> dozen over the past few years) that offers such a service.
    |
    | You've seen it, just haven't called it that. There is no point to
    | it, so it isn't named.

    So you really do have 208Y/120 mixed up with "6 star" or whatever someone
    else might refer to it as.


    |> I HAVE seen a couple three phase setups where a 120/240 volt pole pig was
    |> used, and only HALF of it was wired up to get 120 volts. I HAVE seen one
    |> manufacturer detail that they do make cans with the 120 volt windings in
    |> parallel internally, and still have 3 lugs with one of them not connected.
    |> So these are not necessarily a case of wasting half the capacity. The 3rd
    |> lug may simply be there are part of the process of manufacturing only one
    |> set of empty cans instead of two different sets.
    |
    | Irrelevant manufacturing detail.

    It's very relevant. It decides if the transformer has only 120 volts or
    if it has 120/240 volts. It decides in the case of 2 separate 120 volt
    windings whether they can be paralleled or not (and they need to be in
    parallel for the 208Y/120 service). The only transformer design that
    allows an external choice of configuring 120 volt parallel or 120/240 volt
    series center tapped is one with 4 lugs. I have seen such a transformer.
    But virtually all the rest of 3 lugs or 2 lugs.
     
  4. Guest

    |> Do you know if that home has 208Y/120 or 240DCT/120 ?
    |>
    |> This system is overkill for a single home:
    |>
    |> * *
    |> \ /
    |> *--*--*
    |> / \
    |> * *
    |>
    |> But this system could do the job adequately:
    |>
    |> *
    |> /
    |> *--*--*
    |> \
    |> *
    |
    | ...and the house to the north gets:
    |
    | * *
    | \ /
    | *--*
    | \
    | *
    |
    | ...and the house to the south gets:
    |
    |
    | *
    | /
    | *--*
    | / \
    | * *
    |
    | And pretty soon you have something on the pole that looks kinda
    | like:
    |
    | * *
    | \ /
    | *--*--*
    | / \
    | * *

    It would certainly be possible to deliver three such configurations to
    three different houses from the same pole with three transformers of the
    120/240 split phase design. And you say this has been done? If so, then
    I think that's cool. But that is not what is generally done in 99% or
    more of three phase installations.


    |> Which to choose depends on whether the distribution supply needs to be kept
    |> in balance or not. Utilities require (and this is a reasonable requirement)
    |> that larger services be three phase so they can keep the lines in the area
    |> in balance.
    |
    | Three phase also sorta allows them to deliver more power for a given
    | conductor size.

    When comparing single phase L-L voltage to a delta with the same voltage
    that is true by 15.47%. If you take 240 delta, and compare it to 240
    single phase 2 wire (regardless of where the grounding point is on either
    system), the 240 delta has more power in the same conductor size.

    But if you look at both systems relative to the center of the system,
    the single phase is 2x 120 volts whereas the three phase is 3x 139 volts.
    You get the extra power based on the relative system voltage effectively
    being higher. Compare 120/240 volt single phase to 240Y/139 three phase.
    Put in 6 conductors, 3 per pole for 120/240 volt single phase and 2 per
    pole for 240Y/139 three phase. The latter gets its gain by virtue of the
    higher voltage.

    Compare 208Y/120 to 120/240 and there is no such gain. It's all in the
    voltage comparison where delta allows it to look like it has a lower
    voltage than it really does.
     
  5. Guest

    | wrote:
    |>
    |> | krw wrote:
    |> |>
    |> |> In article <>,
    |> |> says...
    |> |> >
    |> |> > What makes you think that its up to you to chose? The utility
    |> |> > company is going to tell you what is available. The elevator company is
    |> |> > going to tell you what they need, as well. As usual, you're playing
    |> |> > another of your long winded, and useless games of 'What if'...
    |> |>
    |> |> What if Phil bought his own bigass transformer?
    |> |
    |> |
    |> | Progress Energy, who bought Florida Power, wouldn't let you provide
    |> | any transformers. They did the calculations, and set their own
    |> | transformers. Three phase availability was determined by your location,
    |> | but generally any building above a certain level was three phase. Even
    |> | small convenience stores and gas stations are three phase around here.
    |> | The only home I've seen with an elevator had three phase power, along
    |> | with an Onan diesel three phase generator with an automatic transfer
    |> | switch.
    |>
    |> Maybe Florida has no provision to require the utility to provide standard
    |> voltages (like 240 volts). Some other states do. And such a requirement
    |> is NOT a problem to meet (although if you want to change an existing setup
    |> I can expect you have to pay the full costs).
    |>
    |> Do you know if that home has 208Y/120 or 240DCT/120 ?
    |>
    |
    |
    | 208Y/120 They also had a couple 12" wells with three phase pumps,
    | and a diesel powered backup pump.

    OK, so they didn't have any 240 volt supply.
     
  6. Guest

    | charles wrote:
    |>
    |> Power is a function of the voltage squared. So a 3kW heater at 240v
    |> becomes 2.25kW at 208v. It may not be significant if it's used for storage
    |> heating but as an instantaneous heater it would matter.
    |
    |
    | Gee thanks for that lesson. I've know and used it since the '50s.
    | If you need that extra bit of heat, you can buy the proper heating
    | element. Not at the over the counter type 'DIY' dumps, but at a real
    | plumbing supply house.

    Which means it is more expensive. And in many cases they have to special
    order it. I've already experienced the special order cost case with a
    208 volts single phase motor (it was twice as much as a 240 volt motor of
    the same HP and mounting).
     
  7. Guest

    |
    |>Part of the problem is that too many developers and engineers continue to
    |>think inside the 208 volt box. They think it is an accepted norm (and it
    |>is so relative to the people they deal with: landlords and developers who
    |>can shield them from the real problems of residents). So they don't even
    |>think about it. They just whack out a variation of the same old same old
    |>and people are then stuck with no improvement and have to accept it.
    |>
    |
    | Generally, if you are a renter, you experience a lack of choice in
    | many aspects of your housing. You may have lack of choice in being
    | subjected to noise from the Bickersons in the apartment above you or
    | the sax player next door. You may not have the choice of doing your
    | laundry in your unit, or painting your walls lime green, or having
    | your own parking space. If your landlord provides a 240V dryer on a
    | 208V circuit, then yes... your clothes will take longer to dry. You
    | have no choice. The lower voltage might have the dryer heater cycle
    | on for a longer period of time, but the maximum wattage delivered will
    | definately be less.

    Yes, landlords go cheap on lots of things, not just the power.

    The last apartment I lived in had 120/240. The complex consisted
    of 60 some buildings with 12 apartments each. Each building had a
    single phase pad mount. I don't know what its rating was as the
    nameplate was not visible (probably inside and I didn't care to
    get into it). Presumably it could have been as much as 167 KVA,
    the largest single phase pad mount I've seen in catalogs. That is
    probably fine for 12 apartment units.


    | In the US, at least, condo unit owners may have it better, in that
    | they might have a few more things under their control. Most
    | multi-unit condos have an in-unit washer and dryer, so at least you
    | might have a choice about getting the dryer at the correct voltage.

    Yes, if they go buy one for the condo, they can choose between the
    $400 240 volt model and the $440 208 volt special order model. If
    they already have one from the house they now live in and want to
    take it with them, it's probably a 240 volt model.


    | I would argue that its still more of a hassle though (for most
    | people), and it may be hard to find or order the one you want that
    | runs properly on 208V. You will probably be faced with increased
    | expense, as well. Perhaps the one currently on sale has only the 240V
    | element.

    Exactly. The costs for 208 volt models can be from both the smaller
    market as well as the special order handling.
     
  8. Guest

    | wrote:
    |>
    |> | wrote:
    |> |>
    |> |> Maybe you should read some of the tariffs. Most jurisdictions do have
    |> |> some requirements that certain services must be made available of so
    |> |> requested. The only "what if" here is "what if someone knew what they
    |> |> were allowed to really ask for".
    |> |
    |> |
    |> | Obviously, you don't and you've been flogging another dead horse.
    |> | You can take any simple subject and turn it into mind numbing drivel.
    |> | You've flogged this one for a week and made zero progress. Even if you
    |> | got answers, they would only be valid for one location, not the entire
    |> | planet earth.
    |>
    |> How do you know there is "zero progress"? Just because I have failed to
    |> educate YOU on the issue does not mean I have failed to open the eyes of
    |> others to the issues AND solutions.
    |
    |
    | I haven't seen people agreeing with you, or supporting your theories.

    Maybe if you look beyond just who is posting, you'd see more. There are
    already some that are posting, too. The rest are quiet and you cannot
    tell if they agree or not.


    |> | You bitch about no availability of 208 volt appliances. How many do
    |> | you see that are marked 240 VAC only? I see a lot that are marked
    |> | 208-240 VAC. So your water heater is a few volts low. It won't make
    |> | much difference in the output. If you buy at the right places, 208 volt
    |> | stuff isn't hard to find, even in the deep south. If you are in an
    |> | apartment, it is up to the landlord to provide the major appliances, and
    |> | repair or replace them when they quit. So, if the building is big
    |> | enough, they are supplied three phase. no matter how much you want to
    |> | yak about what ifs, no one really gives a damn, except the local power
    |> | company, and the owner of the building.
    |>
    |> I have real experiences with such low voltage issues.
    |
    |
    | Sure you do. We've all seen brownouts. My line voltage was about 105
    | volts for a month while the area was rebuilt after some hurricanes. It
    | was 27 volts for half a day. Fluorescent lights didn't work right at 105
    | volts, but it didn't bother the refrigerators.

    Yes, I have seen brownouts before. Some things work OK at reduced voltage
    and some things done. You get both in each class of appliance.


    |> My grandfather had this issue with his home when he obtained three phase
    |> service for his home to power three phase motors in his shop. He had
    |> problems with a stove that was slow to heat up, an electric dryer motor
    |> that burned out a couple times, and occiaisional issues with the air
    |> conditioning. Apparently he needed 240DCT/120 and they gave him 208Y/120.
    |
    |
    | Apparently he needed the proper appliances. He made the decision to
    | convert to three phase, so don't blame the equipment that he was to
    | cheap to convert, or replace.

    More likely he didn't know. I didn't discuss lots of details with him
    at the time, since I was only 12 years old. I knew WHAT three phase
    was for, but I had no idea how the systems were configured, or that it
    really mattered. What I knew then was that he did say the voltage was
    too low and he was trying to get the power company to fix it.

    I suspect when he asked for three phase, he didn't know the choices
    and might have been expecting to get 240DCT/120. I don't know if his
    shop equipment needed 240 or 208. I just know he was trying to get
    it redone up to the day he died. I don't know why it was not redone.
    I can only guess and many possible explanations seem plausible.


    | One TV transmitter site I worked at was supplied with 480 Wye service
    | only. That was fine for most of the transmitter and cooling system, but
    | the crystal ovens and oscillators ran on 120 single phase so we had to
    | install three 2 KVA 480 to 120 volt transformers to power everything
    | else.

    And the transmitter manufacturer didn't integrate things so that it
    could be connected to a single power source?


    |> I worked in a commercial building at an ISP at the beginning of the
    |> popularity of the internet. As the heat output in the computer room
    |> went up, and it was expanded into a 2nd room, it taxed the A/C system
    |> more. The A/C system was rated for that level of heat, but kept failing
    |> anyway. The building was originally single phase, but was converted
    |> over to three phase many years prior to our occupancy (apparently due
    |> to one tenant installing some equipment that needed some major amount
    |> of power. The A/C systems were single phase, and now running on 208
    |> volts. The A/C servicing company had to special order a 208 volt single
    |> phase motor to replace the 240 volt single phase motors that kept burning
    |> out. Once the 208 volt motor was in, it worked fine.
    |
    |
    | I've lost three air conditioner compressors in the last nine years at
    | my home, and all were running at the rated voltages. Microdyne lost at
    | least a half dozen a year, all were three phase, and running the right
    | voltage. How can you prove it was under voltage, not that the air
    | conditioner couldn't handle the load? Tty air conditioning a TV
    | station's control room and studios. We had a five ton unit just for the
    | VTRs and effects racks.

    The motors burned out very frequently, generally lasting no more than
    two weeks as summer come on along with the new computers in place.
    Once the 208 volt motor was put in, the problem completely went away.
    Clearly the A/C servicing people believed it was a voltage issue.
    Based on what changes took place, I'd agree it was.

    That doesn't mean there can't be failures for other reasons. But in
    the above case, it was clearly voltage with 99% confidence. Go ahead
    and pick on the 1% if you want.


    |> The fact is, there are problems with 208 volt services. Yes, there are
    |> appliances that can work on 208 volts. Some work less well. Some work
    |> just fine. Some will fail.
    |>
    |> If it is a building where the owner buys the appliances, the owner needs
    |> to consider the costs of those appliances as part of the overall cost
    |> savings strategy. In cases where the residents have to buy their own,
    |> such as many condominium arrangemnts, this is a cost passed on to the
    |> residents (so the developer might not give a damn).
    |>
    |> To be cheap, landlords might well buy the very cheapest appliances that
    |> are available, which might be 240 volt just because there is a larger
    |> market for these.
    |
    |
    | Gee, Phil. If the owner has to buy and maintain the appliances, why
    | would they buy the cheapest shit made? They aren't that stupid. Well,
    | at least around here. Their cost for the appliances are in bulk, and at
    | wholesale. A lot of damage to their buildings is avoided by supplying
    | the appliances, and they can charge higher rent. The longer an
    | appliance lasts, the more money they make off it.

    Actually, in a great many cases, they _are_ that stupid. While motor
    based appliances might well burn up, heating element appliances may have
    no issued. BTW, dryers tend to have the motor on L-N, not L-L. So the
    motor would be getting what it expects even on 208Y/120. Ranges and
    water heaters are NOT going to have a shortened life due to running on
    a reduced voltage. So they _can_ get away with using 240 volt stuff on
    208 volts.


    |> Then when residents complain that it takes longer to
    |> cook food and recover heat in the water tank, the landlord just says to
    |> accept it or move out at the end of the lease. Do not under any case
    |> think that landlords will be sure there are no problems.
    |
    |
    | Where is this? Defects in a building can get the landlord and or
    | management company fined. for failing to make repairs in an acceptable
    | time. In severe cases, the building can be condemned. After that, the
    | owner has a little time to do the repairs, and get a new certificate of
    | occupancy. You're just trying to blow smoke up my ass, as usual.

    I'd like to see them get fined for such things. Generally, they don't.


    |> I have pointed out the alternative to get true 240 volts. Not all cases
    |> would be able to utilize that without extra costs. Certainly a retrofit
    |> won't be free. But in many cases it can be a no greater cost to supply
    |> genuine split-phase single phase 120/240 volt service to residential units.
    |
    |
    | Name ONE thing a renter needs to run on 240 volts that isn't supplied
    | by a decent landlord.

    In renting situations, probably nothing. But in at least a lot of cases,
    and maybe most, where 208 volts is supplied, the appliances are 240 volt
    models.

    When the building is converted to condo, the picture changes. And this
    is where most of the reports of this issue come from.


    |> Part of the problem is that too many developers and engineers continue to
    |> think inside the 208 volt box. They think it is an accepted norm (and it
    |> is so relative to the people they deal with: landlords and developers who
    |> can shield them from the real problems of residents). So they don't even
    |> think about it. They just whack out a variation of the same old same old
    |> and people are then stuck with no improvement and have to accept it.
    |
    |
    | They do it because it works reliably, and at a reasonable cost. It
    | really isn't up to you, and there is no valid need for any 240 VAC for
    | anything the owner doesn't supply.

    As long as the landlord supplies correct voltage appliances for whatever
    is supplied, all is well. Sadly, that is not the case quite often.
     
  9. Guest

    | wrote:
    |>
    |>
    |> | charles wrote:
    |> |>
    |> |> Power is a function of the voltage squared. So a 3kW heater at 240v
    |> |> becomes 2.25kW at 208v. It may not be significant if it's used for storage
    |> |> heating but as an instantaneous heater it would matter.
    |> |
    |> |
    |> | Gee thanks for that lesson. I've know and used it since the '50s.
    |> | If you need that extra bit of heat, you can buy the proper heating
    |> | element. Not at the over the counter type 'DIY' dumps, but at a real
    |> | plumbing supply house.
    |>
    |> Which means it is more expensive. And in many cases they have to special
    |> order it. I've already experienced the special order cost case with a
    |> 208 volts single phase motor (it was twice as much as a 240 volt motor of
    |> the same HP and mounting).
    |
    | You were ripped off. Find an honest business to buy from.
    |

    It was like $120 instead of $60. That's no big deal considering the costs
    of dealing with A/C system failures, and having to shut down equipment to
    avoid over heating. The big hassle was it took 4 weeks to get that motor.
    Three 240 volt motors at $60 apiece burned up in the mean time.
     
  10. krw

    krw Guest

    Three transformers can't cost more than a three-phase transformer,
    or they'd do it for the 90% of the poles in existence now.
    I wonder why? Could it be because there isn't a reason?
    Ok, there was confusion on that point. Metering with a current
    transformer would seem to have calibration problems. They really
    need to meter power, not current.
    It *CERTAINLY* is. Look at the voltages on the top of those pigs.
    It is *EXACTLY* what you describe as "six star". We generally look
    at it as three Edison 240V circuits, but it is *exactly* what you
    describe (six 120V circuits - each 60degrees from the next.
    Look again (open your eyes this time). You're not seeing the forest
    for the trees. It *IS* on top of 90% of the poles in the country.
    The other 10% are single phase only, generally found only in rural
    areas.
    Screws aren't expensive. The wires are there. It exists, though
    perhaps a bit different that you describe mechanically.
    Huh? What are you blabbering about?
    Get it through your head, IT'S THE SAME DAMNED THING. When you
    split the three phase ("wye" or delta) into three 240V Edison
    circuits you've just made your "six star". That's done on 90% of
    the poles in the country. As I said above, the other 10% are rural
    single-phase only circuits.
    Good grief Phil, the CT transformer gives you 120V from the A-phase
    and it's mirror, 120V A'. Three of those gives you your "six-star".
    The CT transformers on every damned pole in town. Man, you're
    thick.
    Does it matter? The secondaries are the same phase as the
    primaries.
    Think for a moment.
    DAMN, you're thick!
    You have three phases, each supplying a 240V Edison circuit.
    Connect the dotted lines...
    I *KNOW* that.
    You are master of the irrelevant, Phil.
    A-HA! He does get it! Now look at the voltages on those
    secondaries; your "six-star".
    Phil, I'm not the one who is "mixed up" here.
    Totally irrelevant drivel.
     
  11. Guest

    | In article <>, phil-news-
    | says...
    |> | In article <>, phil-news-
    |> | says...
    |> |
    |> |> |> To make this derived system, you need either:
    |> |> |>
    |> |> |> 1. 3 single phase transformer cores
    |> |> |
    |> |> | Kinda like they do now on the pole.
    |> |>
    |> |> Yes. Except instead of using 120-volt-only transformers (there are such
    |> |> things ... just 2 lugs on the secondary), they need to use the 120/240 volt
    |> |> transformers (plenty of those around) and understand the concept to know
    |> |> how to wire it up.
    |> |
    |> | IF there is any advantage (doubt it), they'll figure out how to wire
    |> | it up. It's rather obvious.
    |>
    |> There is an advantage to having genuine 240 volts. Not all circumstances
    |> make it easy to use separate single phase transformers. The ones that do
    |> would already have multiple transformers. Otherwise it increases cost.
    |
    | Three transformers can't cost more than a three-phase transformer,
    | or they'd do it for the 90% of the poles in existence now.

    I don't have any prices for pole transformers. I do have prices for dry
    type transformers from Eaton/Cutler-Hammer. I picked the following models
    arbitrarily:

    480 -> 120/240 Al 115C 75KVA T20P11F75EE $9,170 (3x = $27,510)
    480D -> 208Y/120 Al 115C 225KVA V48M28F22EE $16,810.00

    Three of those single phase 75 KVA = one three phase 225 KVA. You can wire
    the singles to 120 volts and connect them as wye to be equivalent to the
    three phase one. But you'd pay $10,700 extra for the three single phase.

    The URL of the transformer catalog is:
    http://www.eaton.com/ecm/groups/public/@pub/@eaton/@ee/documents/content/tb00900001e.pdf
    The URL of the price list is:
    http://www.eaton.com/ecm/groups/public/@pub/@eaton/@ee/documents/content/pd08401001e.pdf

    Now if pole transformers had this same issue, I'd expect to see more of
    them as three phase in one can. There must be some reason they don't do
    that. OTOH, three phase in one can is common in many places in the world.


    |> And there are no "6 star" transformers made (yet).
    |
    | I wonder why? Could it be because there isn't a reason?

    There is a reason to have it. There might be a reason not to. That latter
    reason could be ignorance among engineers. More likely it is that customers
    doing the buying (building owners and their construction contractors) do not
    care to make the voltage match. They shave all costs everywhere they can
    and let the resident deal with the losses. They know the vast majority of
    them will know even less than engineers. You could be one of those residents
    and it appears you would not care if your water heater takes 33% longer to
    return to stable temperature.


    |> Maybe there is a confusion here. CT could mean "center tap" or it could
    |> mean "current transformer". In the above, I mean "current transformer"
    |> for the purpose of metering.
    |
    | Ok, there was confusion on that point. Metering with a current
    | transformer would seem to have calibration problems. They really
    | need to meter power, not current.

    I see you don't know how metering with a CT is done. They do meter power.
    A voltage reference is also connected.


    |> What is done in on 90% of the poles? The "6 star" suggest is certainly not.
    |
    | It *CERTAINLY* is. Look at the voltages on the top of those pigs.
    | It is *EXACTLY* what you describe as "six star". We generally look
    | at it as three Edison 240V circuits, but it is *exactly* what you
    | describe (six 120V circuits - each 60degrees from the next.

    Not only do they not exist this way, it is also stupid engineering to do
    so when the service is 208Y/120 (which is the most common type of three
    phase service in the USA, leading 480Y/277 and 240D). The reason it is
    stupid is if you have a pair of 120 volt windings in series and only use
    120 volts of it (which is exactly how 208Y/120 is done), you have wasted
    half the capacity of the transformer. These things cost thousands of
    dollars, and this would be a few thousand dollars of waste for each and
    every one used as you describe. No engineer would ever do that except
    as an emergency temporary means to restore power when a 120 volt can is
    not available.


    |> |> |> Then you need to wrap these cores with 3 primary windings and 3 secondary
    |> |> |> windings. Usually the secondaries go on the inside and the primaries go
    |> |> |> on the outside, so the secondary at lower voltage and higher current has
    |> |> |> less winding resistance.
    |> |> |
    |> |> | Ok, I'm confused. This is different how?
    |> |>
    |> |> The difference is that a traditional E-core 208Y/120 transformer would have
    |> |> only ONE 120 volt winding per core bar (times the 3 core bars). Two such
    |> |> windings at 120 volt each, or a 120/240 volt series winding (connected in
    |> |> series inside the winding instead of at the terminal board) would be needed
    |> |> for the "6 star" configuration.
    |> |
    |> | No different than what happens on 90% of the poles in the country,
    |> | except those are in three cans rather than one.
    |>
    |> The "6 star" is not done anywhere I have ever heard of. You must be
    |> referring to a common WYE, which is not the same thing (WYE is a "3 star"
    |> not a "6 star").
    |
    | Look again (open your eyes this time). You're not seeing the forest
    | for the trees. It *IS* on top of 90% of the poles in the country.
    | The other 10% are single phase only, generally found only in rural
    | areas.

    90% of poles have a three phase "6 star" and 10% have single phase?

    You are on some really nasty drugs, dude!


    |> |> |> Each of the 3 secondary windings needs to be either:
    |> |> |>
    |> |> |> 1. a pair of 120 volt windings which you can wire in series
    |> |> |> 2. a single 240 volt winding with a center tap right in the middle
    |> |> |
    |> |> | Exactly (is there a difference?).
    |> |>
    |> |> Yes, there is a difference. In #1 you have 4 wires coming from the secondary
    |> |> winding to the terminal board. In #2 you have 3 such wires because the
    |> |> winding is series connected, possibly a continuous single wire, inside the
    |> |> winding itself, and just tapped at a mid-point.
    |> |
    |> | A distinction without a difference. WHo cares how many screws are
    |> | on the terminal board?
    |>
    |> You need more screws for the extra wires. How many depends on if
    |> you want to double up on a single lug or not.
    |
    | Screws aren't expensive. The wires are there. It exists, though
    | perhaps a bit different that you describe mechanically.

    You can't just add screws on a terminal board in a transformer. You
    have to put in a larger terminal board to have room to keep the spaced
    apart. It's doable, but is also a big change since you're messing with
    the wires coming off the windings. They put in terminal boards so the
    installing electrician does not have to mess beyond that.


    |> |> It's a difference in construction. Some people might be more familiar with
    |> |> one over the other.
    |> |
    |> | Sure. If there is no reason to make a widget there is a good chance
    |> | that most are unfamiliar with the widget.
    |> |
    |> |> |> All of the center points of these windings are wired/bonded together and
    |> |> |> grounded. Then each of the three phases will have two poles 180 degrees
    |> |> |> apart. Some people will call this six phases.
    |> |> |
    |> |> | Right; split-phase "wye".
    |> |>
    |> |> Keep the "wye" in quotes, then; it's not really wye. I would never call it
    |> |> a wye at all. It's a 6 pointed radial star.
    |> |
    |> | "Wye" is usually in quotes, even in a normal implementation.
    |>
    |> Really?
    |
    | Really.

    Not really at all.

    |
    |> I see it more NOT in quotes. The term WYE is a longish form
    |> of "Y" which is a depiction of a 3 pointed star configuration, not 6.
    |> The "*" more resembles 6 under most fonts (some have 8, but that's
    |> another issue).
    |
    | Huh? What are you blabbering about?

    You have no idea where the term WYE even comes from?


    |> |> |> Which connection pair do you need to ask about?
    |> |> |
    |> |> | I don't. You seem to see a difference between this "star" and an
    |> |> | ordinary 3-phase "wye" that delivers residential 240V split-phase.
    |> |> | I don't see anything new or particularly interesting here, but am
    |> |> | trying.
    |> |>
    |> |> A true WYE is not split phase. That makes a contradiction of terms.
    |> |> But if you know of a manufacturer that makes such a transformer AND
    |> |> calls it "split phase wye" or some such thing, please do point to
    |> |> their catalog reference. I've looked at a lot of transformer catalog
    |> |> info online and have never seen such a thing in a single transformer.
    |> |
    |> | Certainly it is, on 90% of the poles in the country.
    |>
    |> Since well more than 10% of poles have a traditional 3 pole wye, there
    |> cannot be 90% with a 6 pole three phase star arrangement.
    |
    | Get it through your head, IT'S THE SAME DAMNED THING. When you
    | split the three phase ("wye" or delta) into three 240V Edison
    | circuits you've just made your "six star". That's done on 90% of
    | the poles in the country. As I said above, the other 10% are rural
    | single-phase only circuits.

    I know how to make the "6 star".

    If you think it is being done somewhere, take a picture. I want to see
    one with the center lug of all three transformers connected together and
    the other 6 lugs all connected with 6 wires coming off (that is what a
    "6 star" is).


    |> Be specific. First of all you know you need TWO connection points for
    |> a voltage. Simply saying "CT" (which I assume to mean "center tap"
    |> instead of "current transformer") means ONE connection. You get no
    |> voltage from one connection.
    |
    | Good grief Phil, the CT transformer gives you 120V from the A-phase
    | and it's mirror, 120V A'. Three of those gives you your "six-star".
    |
    |> So how do you get 240 volts from a 208Y/120 wired transformer bank?
    |> Answer: you don't.
    |
    | The CT transformers on every damned pole in town. Man, you're
    | thick.

    I know how it is built. Our disagreement is you think it is already
    in use and I know damned well it is not.


    |> |> If you are getting 240 volts from
    |> |> A-B or from B-C or from C-A, and if the phase angles really are 120 degrees
    |> |> as a true three phase WYE would be, then you are going to get 139 volts
    |> |> at A-N, B-N, and C-N. I don't think that is what you want.
    |> |
    |> | It's a "wye" not a delta. Three transformers with CT secondaries
    |> | from A-N, B-N, and C-N. You just made you "star" configuration.
    |>
    |> What are you labeling A-N, B-N, and C-N? The primaries or secondaries?
    |
    | Does it matter? The secondaries are the same phase as the
    | primaries.
    |
    |> Your statement "CT secondaries from A-N, B-N, and C-N" makes no sense.
    |
    | Think for a moment.

    Your statement provides only TWO label letters per phase (for example
    "A-N" for the first one). For the "6 star" you need THREE label letters
    including N in the middle as the center tap.


    |> If there were 3 split-phase secondaries involved, there would be a lot
    |> more connection points than just these three. Even if all the center
    |> taps were connected together, you would still have 6 connection points
    |> to label. Starting at A, that runs to F.
    |
    | DAMN, you're thick!

    Your statements aren't even consistent. You describe transformers that
    have 3 lugs and then you describe 2 lugs?

    The "6 star" has 3 (THREE) lugs PER PHASE (when built with 3 separate single
    phase transformers). You tie the center (CT) lug for all three together and
    you give it just ONE label "N". You ground that one, too. Then you still
    have SIX (that's a 6) lugs. You need SIX (6) labels for them. Three is not
    enough. An example of six labels is: A,B,C,D,E,F



    |>
    |> |> FYI, I did find one utility offering 240Y/139 service for some portions
    |> |> of their service area, as a replacement for 240D.
    |> |>
    |> |> Maybe you are getting ONE phase of 120/240 via ONE split phase transformer
    |> |> tapped to ONE phase (connected L-N) or TWO phases (connected L-L) of the
    |> |> primary distribution lines. But just because there is three phase on the
    |> |> distribution does NOT mean you are getting it. You are most likely getting
    |> |> one of: 208Y/120 three phase (my grandfather actually did get this at his
    |> |> home), or 120/240 single phase, or that old 240DCT/120 setup.
    |> |
    |> | I didn't say an individual home was getting three phase, but it's
    |> | there on the pole. ...including your "star".
    |>
    |> It's not there if what's on the pole is 208Y/120, which most poles
    |> supplying three phase power have. The only voltages available are
    |> 208 volts and 120 volts. Every possible pairing of 2 connections
    |> on these very common setups gives either 208 volts or 120 volts.
    |> I listed them previously. I left none out. None have 240 volts.
    |
    | You have three phases, each supplying a 240V Edison circuit.
    | Connect the dotted lines...

    I know how to connect them. Maybe you do, too. But where you are in
    error is thinking they are already connected up this way. They are not.
    They could be. All you need to do is put three of these split phase
    pole pigs on one pole and wire things up the right way. You'll have a
    neutral (grounded) and 6 (SIX) line wires.


    |> |> |> OK, hope the above helps.
    |> |> |
    |> |> | Nope. I'm still wondering why you see your "star" as any different
    |> |> | than what we see on 90% of the poles in the country.
    |> |>
    |> |> 208Y/120 is _very_ different. 208Y/120 has THREE line wires coming out at
    |> |> 120 degree phase angle equal intervals. The "6 star" (maybe we can call
    |> |> it 240*/208/120) has SIX line wires coming out at 60 degree phase angle
    |> |> equal intervals.
    |> |
    |> |> If I provide you with exactly 3 transformers which are wired up with one
    |> |> winding for the primary voltage and one winding for the secondary at 120
    |> |> volts, it can be wired up by connecting the primaries in whatever they
    |> |> need for the type of service (delta or wye) and connecting the secondaries
    |> |> in a wye configuration. There, you have 208Y/120 just like 90% of the
    |> |> three phase poles in the country (I'll just accept your stats of 90% as I
    |> |> do not know the actual figures).
    |> |
    |> | Look at 100 random poles. You'll see 90 of them wired as 3-phase
    |> | "wye" (really doesn't matter if they are delta). The secondaries
    |> | are CTed, so you have the six points of your "star". Nothing new
    |> | here.
    |>
    |> You really think that?
    |
    | I *KNOW* that.

    You have a camera? Take some pictures! If you find one such setup, that
    is very interesting. If you find 90, that is utterly strange.


    |> Sure, a 120/240 volt split phase transformer used normally for single
    |> phase service could be used for 208Y/120 by connecting only ONE SIDE.
    |> And it might be done in a few places. But it would be very rare since
    |> it is a waste of half the transformer capacity, and thus a higher cost
    |> than needed. They do make transformers that can deliver their entire
    |> capacity on just 2 lugs at 120 volts. There is no center tap. Or if
    |> there is, the center of 120 is 60 so it would not be used.
    |
    | You are master of the irrelevant, Phil.

    Saving thousands of dollars in transformer pricing is VERY VERY relevant.


    |> The majority of 208Y/120 services derived using single phase pole pigs
    |> is done with 3 cans that have 120 volt ONLY secondaries.
    |
    | A-HA! He does get it! Now look at the voltages on those
    | secondaries; your "six-star".

    Those "120 volt ONLY secondaries" are NOT Edison split phase 120/240 as
    is done for single phase service.


    |> |> I have never seen, and never heard of, any "6 star" or 240*/208/120 setup
    |> |> anywhere. I have never seen any utility tariff (I've looked through a few
    |> |> dozen over the past few years) that offers such a service.
    |> |
    |> | You've seen it, just haven't called it that. There is no point to
    |> | it, so it isn't named.
    |>
    |> So you really do have 208Y/120 mixed up with "6 star" or whatever someone
    |> else might refer to it as.
    |
    | Phil, I'm not the one who is "mixed up" here.

    You certainly have a 120 volt transformer mixed up with as 120/240 volt
    transformer.


    |> |> I HAVE seen a couple three phase setups where a 120/240 volt pole pig was
    |> |> used, and only HALF of it was wired up to get 120 volts. I HAVE seen one
    |> |> manufacturer detail that they do make cans with the 120 volt windings in
    |> |> parallel internally, and still have 3 lugs with one of them not connected.
    |> |> So these are not necessarily a case of wasting half the capacity. The 3rd
    |> |> lug may simply be there are part of the process of manufacturing only one
    |> |> set of empty cans instead of two different sets.
    |> |
    |> | Irrelevant manufacturing detail.
    |>
    |> It's very relevant. It decides if the transformer has only 120 volts or
    |> if it has 120/240 volts. It decides in the case of 2 separate 120 volt
    |> windings whether they can be paralleled or not (and they need to be in
    |> parallel for the 208Y/120 service). The only transformer design that
    |> allows an external choice of configuring 120 volt parallel or 120/240 volt
    |> series center tapped is one with 4 lugs. I have seen such a transformer.
    |> But virtually all the rest of 3 lugs or 2 lugs.
    |
    | Totally irrelevant drivel.

    Irrelevant to someone that seems to think all those 208Y/120 three phase
    transformer banks are somehow coming up with more than just three line
    wires.
     
  12. Really? In all of the places I've lived, residential areas had
    single-phase service only: a single MV line running down the top of the
    poles along the street or alley, and single-phase transformers
    providing center-tapped 120/240 service to several houses per
    transformer. Three-phase distribution is used for large customers
    only. Given the amount of area covered by single-family houses
    compared to the area used by commercial/industrial/large residential
    (high rise), I'd have to guess that more than 50% of the total number
    of poles that have any transformers carry one single-phase
    transformer.

    Dave
     
  13. charles

    charles Guest

    obviously very different practices on different sides of the pond.
    Virtually all residential distribution over here is 3 phase. The only time
    I've ever spotted single phase is when an isolated property has its own
    transformer.
     
  14. Guest

    |
    |>Look again (open your eyes this time). You're not seeing the forest
    |>for the trees. It *IS* on top of 90% of the poles in the country.
    |>The other 10% are single phase only, generally found only in rural
    |>areas.
    |
    | Really? In all of the places I've lived, residential areas had
    | single-phase service only: a single MV line running down the top of the
    | poles along the street or alley, and single-phase transformers
    | providing center-tapped 120/240 service to several houses per
    | transformer. Three-phase distribution is used for large customers
    | only. Given the amount of area covered by single-family houses
    | compared to the area used by commercial/industrial/large residential
    | (high rise), I'd have to guess that more than 50% of the total number
    | of poles that have any transformers carry one single-phase
    | transformer.

    Around here there are many areas where three phase distribution exists
    passing by residential locations. The residential dwellings still get
    just single phase. Many businesses, like restaurants, get three phase
    service. There are three transformers. But they get 208Y/120. There
    is no 240 volts in that. Some legacy services for older places do have
    240 delta.
     
  15. Guest

    | In article <fpgbtj$2g3$>,
    |
    |> >Look again (open your eyes this time). You're not seeing the forest
    |> >for the trees. It *IS* on top of 90% of the poles in the country.
    |> >The other 10% are single phase only, generally found only in rural
    |> >areas.
    |
    |> Really? In all of the places I've lived, residential areas had
    |> single-phase service only: a single MV line running down the top of the
    |> poles along the street or alley, and single-phase transformers
    |> providing center-tapped 120/240 service to several houses per
    |> transformer. Three-phase distribution is used for large customers
    |> only. Given the amount of area covered by single-family houses
    |> compared to the area used by commercial/industrial/large residential
    |> (high rise), I'd have to guess that more than 50% of the total number
    |> of poles that have any transformers carry one single-phase
    |> transformer.
    |
    | obviously very different practices on different sides of the pond.
    | Virtually all residential distribution over here is 3 phase. The only time
    | I've ever spotted single phase is when an isolated property has its own
    | transformer.

    But homes in UK generally only get one phase at 240 volts. Some parts of
    the world, though, do typically provide three phase to a home, making 380,
    400, or 415 volts available.
     
  16. charles

    charles Guest

    true, most homes only have a single phase (although I have all 3) but the
    local distribution is 3 phase.
     
  17. Guest

    | In article <>,
    |> | In article <fpgbtj$2g3$>,
    |> |
    |> |> >Look again (open your eyes this time). You're not seeing the forest
    |> |> >for the trees. It *IS* on top of 90% of the poles in the country.
    |> |> >The other 10% are single phase only, generally found only in rural
    |> |> >areas.
    |> |
    |> |> Really? In all of the places I've lived, residential areas had
    |> |> single-phase service only: a single MV line running down the top of the
    |> |> poles along the street or alley, and single-phase transformers
    |> |> providing center-tapped 120/240 service to several houses per
    |> |> transformer. Three-phase distribution is used for large customers
    |> |> only. Given the amount of area covered by single-family houses
    |> |> compared to the area used by commercial/industrial/large residential
    |> |> (high rise), I'd have to guess that more than 50% of the total number
    |> |> of poles that have any transformers carry one single-phase
    |> |> transformer.
    |> |
    |> | obviously very different practices on different sides of the pond.
    |> | Virtually all residential distribution over here is 3 phase. The only
    |> | time I've ever spotted single phase is when an isolated property has
    |> | its own transformer.
    |
    |> But homes in UK generally only get one phase at 240 volts. Some parts of
    |> the world, though, do typically provide three phase to a home, making 380,
    |> 400, or 415 volts available.
    |
    | true, most homes only have a single phase (although I have all 3) but the
    | local distribution is 3 phase.

    But the only three phase system you can get is a star (what is referred to
    as "wye" in the USA). You can't get delta. And you can't get "6 star" (as
    I call it) nor would you have any reason to need it (because no appliances
    would ever assume 480 volts on a single split phase system). Do don't have
    the voltage assumption issue the USA has.
     
  18. krw

    krw Guest

    Where do you live, Mongolia? The only places I've seen single phase
    distribution is in the middle of the country (rural Vermont, in
    fact).
    Your *guess* is wrong.
     
  19. krw

    krw Guest

    Different issue. My father wanted three phase into his house in the
    late '50s. He argued that it was on top of the pole already so it
    was a simple matter to bring it down to the entrance panel. They
    told him that they would do it if he guaranteed a $100/month bill
    (rather steep for the '50s).
     
  20. Currently, the area around Vancouver BC. Other residential areas with
    single-phase service: near Waterloo, Toronto, and St. Catharines
    Ontario, near Montreal Quebec.

    Where do you live that has full three-phase MV on top of every pole on
    every street in a residential area? And three transformers on every
    pole that has a transformer?
    Not where I live now, nor where I've lived for decades. Again, where do
    you live that has 3-phase on the pole outside every house?

    Dave
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-