280V motor on 230V circuit

------------- 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.

--

Don Kelly dhky@shawcross.ca
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>

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.

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.

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Ian

? "daestrom" ?????? ??? ?????? news:4828b130$0$7047$ snipped-for-privacy@roadrunner.com...

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.>

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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:-) (

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Thanks for your (and esp. daestrom's) explanation on how they work.

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.

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.

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.

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.

In alt.engineering.electrical Tzortzakakis Dimitrios wrote: | | ? ?????? ??? ?????? | news: snipped-for-privacy@news5.newsguy.com... |> 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?

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| Phil Howard KA9WGN (email for humans: first name in lower case at 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. |>>

|>

|> 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.

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| Phil Howard KA9WGN (email for humans: first name in lower case at 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.

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| Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) |

| 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.

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| Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) |

In alt.engineering.electrical Ian Jackson wrote: | In message , Thomas Tornblom | writes |>"Michael A. Terrell" writes: |>

|>> Thomas Tornblom wrote: |>>>

|>>> "Michael A. Terrell" writes: |>>>

|>>> > snipped-for-privacy@panic.xx.tudelft.nl wrote: |>>> >>

|>>> >> In sci.electronics.repair jakdedert 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.

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| Phil Howard KA9WGN (email for humans: first name in lower case at 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).

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.

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| Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) |

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)

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.

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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).

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