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280V motor on 230V circuit

Discussion in 'Electronic Repair' started by Deodiaus, Apr 26, 2008.

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  1. Guest

    |
    | 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.

    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.
     
  2. Guest

    |
    | |> In alt.engineering.electrical Michael Moroney
    |>
    |> | 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.

    Isn't it just inductance in series? Shouldn't that just be a phase shift as
    seen from the primary side?
     
  3. Don Kelly

    Don Kelly Guest

    ----------------------------
    --------
    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).
    --------------
    -------------
    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. --------------------------
    "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.
     
  4. Don Kelly

    Don Kelly Guest

    ----------------------------
    -------------
    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.
     
  5. 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.
     
  6. 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.
     
  7. Ian Jackson

    Ian Jackson Guest

    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.
     
  8. You mean a secondary and a tetriary? The transformer for the hotel load of a
    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.
    Quite the same principle is done with diesel locomotives and is called
    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.
    The one we have here operates with a motor.
    I had no idea how it really works, but I got the general idea.>

    --
    Tzortzakakis Dimitrios
    major in electrical engineering
    mechanized infantry reservist
    hordad AT otenet DOT gr
    NB:I killfile googlegroups.
     
  9. I cross my fingers that terrorists get no electrical engineering degree:0
    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:) (



    --
    Tzortzakakis Dimitrios
    major in electrical engineering
    mechanized infantry reservist
    hordad AT otenet DOT gr
    NB:I killfile googlegroups.
     
  10. James Sweet

    James Sweet Guest


    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.
     
  11. Guest

    |
    | ? <> ?????? ??? ??????
    | |> In alt.engineering.electrical Tzortzakakis Dimitrios <>
    |> 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?
     
  12. Guest

    | ----------------------------
    | |>
    |> |>> In alt.engineering.electrical Michael Moroney
    |>>
    |>> | 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
    | -------------
    | 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.

    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.
     
  13. Guest

    | 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.
     
  14. Guest

    | 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.

    Is this the system where the voltage is 133 volts relative to ground and 230
    volts between phases (and formerly 127 volts relative to ground and 220 volts
    between phases)?

    If they still use that system, then I'm interested in buying a UPS designed
    for that. But it is my understanding it is phased out in cities and hard to
    find anymore in rural locations.
     
  15. Guest

    | In message <>, Thomas Tornblom <>
    | writes
    |>
    |>> Thomas Tornblom wrote:
    |>>>
    |>>>
    |>>> > 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.
    |
    | 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.

    What I have heard is that teh distribution system is not changing, but new
    service installations will be supplied with 230V unless 240V is specifically
    requested ... after some point in time that may not have come, yet. What
    I heard is they don't expect to have all of UK changed over for many decades,
    and maybe even a century or so.
     
  16. Guest

    | 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).

    What about multiple parallel transformers, or at least multiple parallel
    windings on the same core (on whichever side the tapping is to be done),
    where the taps are stepped incrementally on each winding? Instead of a
    shorted winding segment, you'd have windings of differing voltage in
    parallel as each of the windings change their taps one at a time.
     

  17. Some years ago I worked at an Air Base in Northern Thailand. the
    airfield lighting was a constant current series circuit and used
    transformer as you describe - a movable core winding that was driven
    in and out of the outer windings by a motor controlled by a current
    sensing system.

    I believe that street light systems are similar.

    Bruce-in-Bangkok
    (correct Address is bpaige125atgmaildotcom)
     
  18. Benj

    Benj Guest

    Since I'm posting from GoogleGroups I can't respond to Phil, but the
    rest of you can be enlightened.

    In 120/240 or similar systems there is not the freedom to choose this
    ratio. The wiring of the source transformer determines it. As others
    have noted, in the "Edison" U.S. system the source is a center tapped
    transformer with the center tap grounded. This makes a two phase
    system with each 120v "leg" 180 degrees out of phase with the other
    one. The ratio of the high voltage (240v) and the low voltage (120v)
    is always therefore 2:1.

    In a three phase system there will be three transformers with
    secondaries (one for each phase) wired in a "star" or "Y"
    configuration. This is necessary because you need the center point of
    the "star" or "Y" to be ground for each low voltage phase. If you wire
    with a "delta" configuration there is no central grounding point
    available for the individual phases. IN three phase circuits the
    relationship between that individual phases to ground (say 120v) and
    the voltage measured between phases is not arbitrary. It is always
    determined by the square root of 3. Hence the between phase voltages
    being sqrt 3 x 120 = 208V. Just like the two phase system these
    ratios are determined by physics and can't be arbitrarily set.

    Of course there is the issue that electric companies often will name a
    voltage one thing while actually supplying an other for small
    variations about the "standard" voltage.
     
  19. Professional washing machines. One of my very first days 'in the field' was
    to connect some of them. They have a large heating element, you can connect
    it single phase, or 3 phase, it just heats up faster (of course) when you
    connect it 3 phase. (they have a single phase motor, so it works also in
    pure 230 V).


    --
    Tzortzakakis Dimitrios
    major in electrical engineering
    mechanized infantry reservist
    hordad AT otenet DOT gr
    NB:I killfile googlegroups.
     
  20. This is for sure in ICE, where they get 15 kV 16 2/3 Hz AC from the
    cetenary, and they convert it to 3 -phase AC for traction motors (3 phase
    induction), and they also use regenerative breaking.There's also the french
    TGV (Tren de Grand Vitesse) and the just new by Alstom (www.alstom.com) AGV
    (Autometrisse de Grand Vitesse). Classic E-Loks have regular breaking, and
    AC motors with series excitation, designed to work at 16 2/3 Hz. (Just like
    the ones you'll find in a drill, but much larger, at 1 MW or more). They are
    called universal motors, in the small scale, because they can work both in
    AC and DC. I'm wondering, how large their brushes are... In the 300 MW turbo
    generator, the brushes that suplly the excitation current, are as large as
    bricks. Newer type of turbo generators are brushless. The speed record for a
    classic E-Lok is held by Siemens' Taurus, IIRC 180 km/h with 12,000 HP.
    I have no idea about train driving, but in Germany I got a local train from
    a small city to Mannheim, and the Lokfuehrer (train driver) was driving it
    like a race car... He accelerated fully to 130 km/h, and when he was close
    to the next stop, he braked fully, too. It had one E-Lok, and two cars.
    Also, the ICE starts like a race car. It's longer than 500 m, 12 cars, and I
    think it accelerates to 100 km/h in 10 seconds.
    Yeah, right, and the transformer is cooled by active oil cooling (that means
    that the oil cools the trasformer, and there's a separate oil cooler. Like
    the intercooler used in the tanks where I served at army, but that's a
    differrent story).
    But isn't a locomotive by itself heavy enough? Like 120 tons and above, with
    fuel and all?
    (Check at www.wartsila.com some large diesels). In our new power station,
    they have installed two 50 MW, 70,000 HP two-stroke diesels. To see how
    2-stroke diesels work, look in www.howstuffworks.com.. The ships that travel
    from Iraklion to Piraeus (the harbour of Athens) the new ones, have 4
    Wartsila 12 V 46 4-stroke diesels. 12 is number of cylinders, in V, and with
    a diameter of piston, 46 cm. When they travel normally at night, they fire
    up 2 engines. But, when they make a day trip, they fire up all 4 engines at
    full throttle, and the whole ship vibrates. A ship is the only place you can
    get free electricity. In my last trip, I saw young students plugging their
    laptops to the ship's receptacles. A free lunch, after all:)
    I have no idea what they are doing in continental Greece, they *should* have
    electrified all routes.



    --
    Tzortzakakis Dimitrios
    major in electrical engineering
    mechanized infantry reservist
    hordad AT otenet DOT gr
    NB:I killfile googlegroups.
     
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