Wiring question

[Don Murray]

An autotransformer, we use them all the time to get people in full power. All you need are 2 good wires. You can make the third.

Don

[DJ Delorie]

That doesn't change phase. But now that I think of it, they do make phase converters using a motor and a generator.

[Leo Lichtman]

"DJ Delorie" wrote: (clip) My primary motivation, other than to have some fun on a Friday, is to keep people from confusing single-phase house current with the original two-phase (4 wire, 90 degrees) AC invented by Tesla. This

2-phase was replaced with our current 3-phase (3 wire, 120 degrees) power. ^^^^^^^^^^^^^^^^ I don't think anyone was trying to say that 220v power coming to the house is "two phase." Two phase power requires a 90 degree lag (or lead) between the phases.

If you look at two voltages on an oscilloscope, and see one reaching its positive peak while the other is reaching its negative peak, is one 180 degrees out of phase with the other? According to your thinking, it depends on the source. If its coming from a center-tapped transformer, it's not a phase difference, but a polarity reversal. If it's coming from generator windings that are positioned on opposite sides of the stator, it would be a 180 degree phase difference.

Suppose its coming out of a black box?

[Patrick Conroy]

DJ Delorie wrote in news: [e-mail]:

In true Usenet-Wreck-ElectricityThread fashion! :)

[DJ Delorie]

Since you said "positive peak" and "negative peak", no. Had you said "most positive" and "least positive", yes.

I think the answer depends more on stuff other than the signals themselves. If you measure between the signals, and the result isn't the simple subtraction of the two signals, it's a phase difference.

What if you had a 120VAC signal, and a 12VAC signal of opposite polarity? Are they out of phase? What about 120VAC and a -12VAC signal of opposite polarity (the signs cancel and you get the "same" polarity)? Good thing it doesn't matter in practice. Of course, if it *did* matter in practice, it would be because of a measurable difference, and then the answer would be obvious ;-)

My scope has an "invert" switch that further confuses the issue.

Then it doesn't matter. Usually it's a matter of definition, not evidence. On the schematic, the signals would be labelled relative to the circuit's common ground, and as to whether they were defined by voltage or phase. It matters a lot more when the shape of the signal is asymmetric (like a pulse or ramp). An inverted pulse is *way* different from an out of phase pulse.

In the case of house current, since we *do* use the 240VAC voltage offering, the definition is one of voltage, not phase. You use all of the voltage, or half of it. If you had three phase power, you couldn't add the three voltages up to get a single 3x voltage, so the definition is one of phase. You normally have three phase power because you're taking advantage of the phase differences, not the range of voltages you get.

[Leif Thorvaldson]

====>I would still like to know if the cat in the black box is alive or dead? *TIC*

Erwin

[Martin H. Eastburn]

Your one high voltage (really medium or somewhat low for service) is a single phase of a larger 3 phase system.

It is used to drive a input of a transformer - the other side is earth ground.

The secondary is then generating single phase voltage - but if there is a center tap, then the far two ends of the secondary with reference to the center tap are out of phase and typically 180 degrees. This is 220 service. There are unique transformers that can generate twisted star voltages and phases but the are not at homes. (Canning factories yes...).

If the center tap is open - and you measure from one end to the other - appearances change again for the same stuff.

Martin

[DJ Delorie]

"Yes"

[DJ Delorie]

Yes, I'm well aware of all that. Heck, I know how to *make* those transformers.

Typically? What, on alternate Tuesdays it's only 170 degrees?

No, it's 240 service.

No, they can *convert* voltages that are already three phase to other three phase voltages. They come in delta and wye configurations. An isolation transformer can extract one of the phases and yield a single phase service, but no simple transformer can turn N phases into >N phases.

Maybe not *your* home.

[Martin H. Eastburn]

Special angles for smart assess on Tuesdays. Actually - I'm a Physicist. I know that the center tap is not perfect. So the end phases are not perfect. That is the fact of manufacture. My brother makes Utility Transformers.

IT depends on your high line service and if the high line was kicked up to allow more power or not.

I have lived using 110, 112, 115, 120, 125, 130 volts on home wall plugs.

You don't know poly phase power. Three phase is baby talk to high power and special power use. 7 and 9 phases is common. The ends of the stars(Wye to advanced versions) are phase shifted and are tapped. These are used in precision motor control. Who said simple transformers are used. You did I didn't. Phases are simply a relative voltage or current measurement with reference to another. Many places have 220 single ended to Gnd. Two wires. We in the USA, typically have double ended supplies with a central neutral that we use as a point of reference.

You have 7 or 9 phase ? - wow - I'm surprised. But then maybe you shop is in a old CANCO plant that used German sheet metal to can presses.

Yes, I have single phase and soon three phase. I have no need for Poly phase at this time.

Martin

[Morris Dovey]

| ====>I would still like to know if the cat in the black box is | alive or dead? *TIC*

"No"

-- Morris Dovey DeSoto Solar DeSoto, Iowa USA

[Don Murray]

7200V phase to ground is one leg of a 3 phase 15KV system, which is about normal. There is older 4160/2400 primary and there is also higher voltage primary. We operate a 20.8KV system that's 12KV phase to ground.

His 7200V transformer would be a phase to ground, but the other side isn't just grounded, it is either hooked to a primary neutral or most likely a common neutral. Both are metallic returns to the substation, both are grounded at the substation. Common neutrals are common to the primary and the secondary and have 3.5ohm grounds or less every 1000' under the main line and at the end of all taps.

There are unique

Show me a twisted star. This one pegged my BS meter.

Don

[Leo Lichtman]

"Leif Thorvaldson" wrote: I would still like to know if the cat in the black box is alive or dead? ^^^^^^^^^^^^^^^^ Unless you know of a third possibility.

[Don Murray]

It's not really a center tap. There's two separate coils on the secondary and for a 240 transformer the 2 coils are in series, and the center point is connected to a bushing and brought to the outside of the can. The same transformer can be used on a 208 service by parallelling the secondary coils inside the can. Didn't your brother explain this to you?

More BS. If you have anything to back this up, show me.

More BS. Granted years ago there was 110, and now the service voltage is

120 plus or minus 5%. But nowhere in the United States has 130V in wall plugs. If they do show me.

Don I have been doing line work for 33 years, as an apprentice, lineman, line foreman, and for the last 20 years as a troubleshooter for the power company.

[Kevin Miller]

After a 220 volt hit, I'd say that Mr. Shroedenger (sp?) won't need to stock up on the Friskie's any time soon! ;-)

...Kevin

[Leo Lichtman]

"Don Murray" wrote: It's not really a center tap. There's two separate coils on the secondary and for a 240 transformer the 2 coils are in series, (clip) ^^^^^^^^^^^^^^^^^^ I think what he meant was that the windings on both sides of the center tap may not be identical. This could be true whether or not it is a literal "center tap," or an electrical equivalent obtained by hooking two windings in series, with a lead coming off. This would result in a VERY tiny inequality in the voltages on both sides of neutral. It would NOT result in any deviation in the phasing on the two sides of neutral.

This would hold true on Tuesdays, as well as other days of the week.

[David C. Stone]

This is what the blink tag is for:

Schroedinger's cat is not dead!

[Martin H. Eastburn]

Tish tish - never had 125 or 130 - must live in un-developed area of the u.s.

I have lived all around the country and over seas - grew up in a town that was growing left and right. I just left the left coast were 130 was common due to the explosion of houses drawing power... More power at the same current...same wire.

I was a professor for years and aided Electric Power and Transmission companies and Electric service companies in learning and teaching - and understanding odd things.

My lines into this 1500+ deep lot have 4 transformers on them for just me. One for the shop as my 200amp service, one for the house and its 200amp service and then another line and pole at the back of the lot (more money wasted - not) with a transformer on each high line. Yes - I have 2 of a three phase high voltage set. The transformers at the end are there only for transmission line (as in RF and transmitters...) termination at the far end. Transients slam those transformers, not mine. They are larger and the secondaries fly in the air.

Martin

[Martin H. Eastburn]

Don - Sounds like you are in the trade. Guess you didn't see the canning factories bit. Motors are three or more phase there.

They are 7, 9, 12, 15 - strange stuff. What that is all about is this :

Take your 'normal' three phase WYE or star then part way out on the arms re-direct the phase angle and then sometimes redirect again the re-direct.

These smaller windings out on the end of the winding (in the circuit) are for shading coils on the motors, coils, and other controls.

They have their energy in a different time domain as the main line coil. Lead or lag, they are effective push or pull or pre-initialize and the like.

I have a ton of books to go through to find a twisted design - I thought my Motor repair manual would have it - but didn't see it, then both electricians and electrical engineers standard handbooks a quick glance - not yet...

I doubt my steam boiler engineering book has it or my High speed signal propagation boo, has. But it was extracted once for my college notes and aided an electric company service man (a friend as well) understand 3 phase with these nasty phases - more wires and binding posts than most. The instructions stated that a single mis-wire would jam the machine. The pressure was on.

Martin

[Robert Bonomi]

No there isn't. It's *been*done*. many times, many ways. google for "quatrature amplitude modulation", for a _relatively_ easy-to-understand example.