# Wiring question

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• posted on August 22, 2005, 2:00 pm

You just *THINK* you're being a smart-ass. :)
Given the quality of the wiring in the building -- and that I got a measured seven-volt drop at the wall outlet when I kicked on a piece of gear that drew a whopping 8 amps -- I *do* expect the first-floor folks _were_ seeing significantly higher voltages. Simply by virtue of being on significantly shorter runs of that antique 'house' wiring.
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• posted on August 22, 2005, 6:32 pm
Robert Bonomi wrote:

208V is a common service voltage. You still have 2 120V hot legs to neutral. You find these in apartment buildings, shopping centers, office buildings, strip malls and warehouses, but it would be very rare to have one in a single family dwelling.

This just backs up what I'm saying. 130V in a wall outlet is just wrong. In your case in the apartment building, it was probably a 120/208V service, in which case the problem was the regulator back at the substation. Most times when I see 130V on one hot leg, it's a neutral problem on a 120/240V service.
Don
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• posted on August 22, 2005, 7:28 pm

I used to live in such a building. 54 units, each with two phases run into the apartment (each line of apartments got a different pair of phases).
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• posted on August 22, 2005, 4:08 am
writes:

SNIP ..........

=============================Technically true, but in practice, a wye primary can be used with a delta secondary allowing, when rectified, a 12 pulse output rather than the 6 pulse of either the dellta/delta or wye/wye. This feature is used in X-ray generators to achieve near DC levels at the X-ray tube.
Ken Moon Webberville, TX.
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• posted on August 22, 2005, 7:33 pm
Ken Moon wrote:

Ken
I don't doubt that X-ray machines have special transformers in them for their needs. But for distribution transformers a wye primary and a delta secondary is very common, as is a delta primary and a wye secondary. The determining factor on whether the primary is going to be wye or delta is the actual line voltage and the nameplate rating on the transformer. For example, we have a 12KV 3 wire primary that is 12KV phase to phase and 6930V phase to ground. And we also have a 20.8KV 3 wire primary with a common neutral that is 12KV phase to ground. And we stock 12KV transformers. So if you are going to hang a bank in the 12KV primary, it will be delta. And if you hang a bank in the 21KV primary, it will be wye.
The determining factor on whether the secondary is going to be delta or wye is the voltage that you want to serve. If you are going to serve a 120/240V 3 phase service the secondary will be delta. And if you are going to serve a 120/208V 3 phase service the secondary will be wye.
Note: to serve a 120/208V service we must pull the lids off the transformers and parallel the secondary coils inside.
So by stocking 12KV 120/240V transformers we can use these in both primary systems and serve 120/240V 3 phase, and 120/208V 3 phase and 120/240V single phase.
Next week we'll be covering VARS (volt amps reactive) captive reactance and inductive reactance, circulating current, fault current, third harmonic overvoltage, and ferro-resonance. :)
Don
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• posted on August 20, 2005, 4:24 am
Martin H. Eastburn wrote:

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
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• posted on August 21, 2005, 4:04 am
Don Murray wrote:

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
--
Martin Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
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• posted on August 21, 2005, 8:55 pm
"Martin H. Eastburn" wrote a delightful piece of science fiction. ^^^^^^^^^^^^^^^^ Don, it pegged my BS meter, as well. Also my entertainment meter. Martin, you are in the wrong forum--this needs to be submitted to Rec.Ent.Sciencefiction.
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• posted on August 22, 2005, 2:19 am
Leo Lichtman wrote:

You guys are just not up to speed on custom large factory Production machines.
I have been turning wood since 1957 on and off. Have to turn a handle for the 2" wide steel wrench I cut with my cnc plasma torch. It will be in Walnut.
I have been designing electronic and electrical things since before that date. National Science Fair first place winner in 57. That was the weirdest year in my life. Having 3 wings of B-52's in battle dress form up and head East while I was on the play yard.
Yes I have seen it - done it - been there and had it done to me.
The CANCO plant - makes cans from sheet metal - that was or still is in Arlington Tx was the place with this nasty transformer and motor. Three phase normal to nasty.
I think you guys are good in your trade but never ran across this stuff and so it is out of your background.
Ever see a 10,000 amp Ignatron (Mercury tube with an igniter ) They are used to electro plate large metal items - like whole cars or truck bodies. They are getting old now - going to solid state stuff but I bet some are still around.
Martin
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Martin Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
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• posted on August 22, 2005, 2:26 am
"Martin H. Eastburn" wrote: (clip) I think you guys are good in your trade but never ran across this stuff and so it is out of your background. (clip) ^^^^^^^^^^^^^^^ Some of the things I have never seen do not exist.
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• posted on August 22, 2005, 4:19 am
Leo Lichtman wrote:

Like the sound in the forest or the semi-tractor at the 4-way stop ?
There is a lot of things I haven't and won't also. Martin
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Martin Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
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• posted on August 22, 2005, 6:49 pm
Martin H. Eastburn wrote:

Martin
I did see the bit about the canning factory in your other post, and dismissed it. The fact of the matter is when your can company or your chrome plating company or some of the companies in my service area, like, Airco, Blue Diamond, and Aerojet, have a problem with the power being served them by the utility, I'm the guy that shows up. Also when the Police call when there's a pole in the road that a car's knocked down, or the Fire Department calls because they want the power shut off to a burning building, or someone calls because they want the power shut off to change their panel or a main breaker, or a little old lady calls that just changed a fuse and her power still doesn't work, I'm the guy that shows up.
I run into a lot of plant mechanics, maintanence workers, maintanence engineers, and various other titles that are responsible for the electrical systems in their plants, and I'd have to say it runs about 70/30 to the ones that have a good understanding of their electrical systems and ones that are winging it. I spend a lot of my time educating the 30% that don't.
Don
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• posted on August 23, 2005, 3:08 am
Don Murray wrote:

Don - both good and bad for you. Nice to be at the forefront of power but sometimes when fire is flicking in a storm - we want you there last.
I used to live in a Coastal Redwood forest. I always hated to see the guys come in from the flat land central valley to help out. It was great training, but very dangerous for them. At home, a bucket truck could do everything. Only the power station high lines would need special help, but that was someone else. These young men would have a fallen Fir that was maybe 48" at 4' across a road being held up by the telephone line. The power lines snapped the insulators off the poles. To make things worse, the tree was across a steep narrow road. Cutting the trunk would allow a killing log to roll and the size was much to big to 'tie up'. Finally the short end was tied up in a spider web of lines to every tree they could find. A crane at risk down-hill would hold up a short section as the big tree saw came to play. That was not for those to learn, but someday they might be training someone else. The tree had fallen across most of the width of my property. Tons of limbs.
Martin
--
Martin Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
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• posted on August 21, 2005, 5:39 pm

No there isn't. It's *been*done*. many times, many ways. google for "quatrature amplitude modulation", for a _relatively_ easy-to-understand example.
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• posted on August 19, 2005, 5:03 pm

The relationship is not symmetrical.
It's relatively easy to generate two signals that are 180 degrees out of phase, each of which can be measured relative to a common ground, but show no voltage difference relative to each other. Think of two relays (or light switches) which take turns turning a circuit on. You can measure the output of either relays' contacts to ground, and see the signal, but if you just connect from one relay to the other, you get nothing.
In the case of a multi-tap transformer, the fact that it's a multi-tap transformer is enough to make it a voltage issue rather than a phase issue. Consider a transformer with ten taps. Are there ten phases? Of course not, but there are ten (er, plus or minus a fence post) voltages, which you can use in any [linear] combination, much like putting batteries in series.
Now, if you had two identical transformers, and wired one backwards, *then* you'd have a phase issue (still, though, no practical difference). But like I said earlier, there's no practical difference when we're talking about house current.
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.
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• posted on August 19, 2005, 5:51 pm
"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?
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• posted on August 19, 2005, 9:39 pm

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.
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• posted on August 19, 2005, 5:08 pm
DJ Delorie wrote:
After all, you only have

Actually, there are two secondary coils on the transformer, and they're in series in this application. But there are other times when they are in parallel. You can have a look at my website, and see some transformer connections, including phase angles, that I had up for a discussion on another NG. They are the most common three phase connections used today.
http://murrayranch.com/Electricity.htm

There is also a 5 wire. On my web page you can see the Scott connections that require special transformers to serve these obsolete loads from modern three phase power. These are very rare today.

So am I :)
Don
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• posted on August 19, 2005, 5:56 pm

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• posted on August 19, 2005, 8:47 am
220VAC is 2 legs of 110VAC out of phase with each other. Therefore, the 220VAC is across those legs. Sometimes there is also a neutral wire included which allows the outlet to also offer 110VAC. This configuration is typical for a cloths dryer where the timer runs on 110VAC and the heaters on 220VAC.
For wiring 220VAC in your shop, I recommend pulling cable with 2 hots, 1 neutral and 1 ground. The motors in your machines don't need the neutral, but it's handy to have there if you need it in the future.
Bernie