Hi Kerry.

Yes, I know the fuses on the top of the pole that are very big are indeed rated PRIMARY voltage --- might be 7200 or something else.....7200 is very common though.

What I meant when I said 120v is only coming from 1 leg FROM the transformer is that maybe one of the windings in the transformer went out....so the other 120v leg is dead.

OR what might be going on......is different transformers are used to feed different legs of a secondary 120v circuit on the poles.......and it's configured incorrectly.

A call to your power company.....if you could ever talk to a lineman or engineer would straighten it out.

YOU are sure that one leg of your fuse panel/box is not off, correct???

The linemen brushed me off like an irritating mosquito. Excel Energy sent two linemen each in their own truck to solve the problem. They were prowling the alleys a couple of blocks away with the searchlights on their trucks, looking for the problem. I went up to one of them and told them their problem was on pole X a couple of blocks away. He looked at me like I was an idiot and drove away still flashing the searchlight. When he got to the pole I had indicated, he flashed the spotlight up the wrong side of the pole, didn't see anything and kept prowling the alleys. A number of minutes later he came back to the pole, looked again and saw the blown fuse.

.........LOL..........you get to talk to people who barely know their own name.

You NEVER get to talk to a person with some intelligence.


I want to speak to Dell to find out which onboard video they are using on their motherboard on a specific desktop. NFW can you get an answer to this question. Every single one of them reads the same script that I can read right on their website.

nice physics lesson.

I am glad I don't have that situation in either house, as they both have 220 water pumps.

We try to please.

With one leg open to a domestic dwelling the meter does not work was something I did not know. Interesting to say the least.

This of course must only apply to meters made for application on two legs. At one time single lead feeds where quite common I suppose.

It is not a bad ideal to check your incoming voltage to a dwelling though. If substandard it is hard on motors although light bulbs might last longer. Different areas probably have different minumins. Higher end of the allowable range voltages of course reduce the power bill.

There's a pretty good discussion with diagrams here: More Delta Vs. Wye Transformers

It's not a perfect apples to apples comparison since it shows 120 v legs on the wye and 240 legs on the delta, but that's what's needed to deliver 120 via those transformers.

I think for Kerry's original question, the answer is very much "it depends...". In San Antonio, for example, the energy company publishes its standards and there are numerous notes and exceptions. The "standard" delivery is published as 120/240 with three-wire grounded neutral; but there's a permissible exception for multi-residence that gets 120/208 single phase three wire as long as certain conditions are met. Or you might be on the "downtown grid" and use 208Y/120 from a four-wire, three phase wye. There does not appear to be a "standard" high voltage across the city; you might have 240 or might have 208.

For BC's maybe rhetorical, "how do you get 240/120 from a three phase system" question: you only use one phase and a center tap on a delta. It might be cheating, since you're not using all three phases, but the center tap gets you 180 degrees out of phase.

There's probably a "guide to identifying transformers on poles" website somewhere, if Kerry really wanted to follow up and figure if he's got wyes or deltas in his rentals.

I think I got my original question answered, roughly. Since the extent of my official physics education was a non-regents high school physics class in 1970, much of the electrical discussion is over my head. I know heavy duty electrical motors require three phase electricity and light duty single phase. I assume since the phases are expressed in degrees this has something to do with the current alternating as the generator spins thru a single cycle. A layman's explanation of these phases, what is happening and their significance would enlighten me.

I find it somewhat amazing that the power company must resort to this approach with the huge load unbalance caused by the inability to send the high leg to any residence.

I honestly do not see how they can possibly balance the loads using a center tapped Delta setup. I read some reference to two transformers in series to accomplish this task. It would appear that it would be impossible to run an entire residential grid using a center tapped Delta setup.

A 3 phase generator has 3 magnets. Each magnet has a north and south pole. The magnets rotate at a set speed inside of a Stationery (Stator) winding. As a magnet passes a coil of wire it "cuts" the magnetic lines of flux causing a voltage to be induced into the coil of wire.
http://upload.wikimedia.org/wikipedi...y_currents.jpg


The 3 phase is because the magnets are 120 degrees apart. All of this happens at a rate of 60 times per second. Which gives us 60Hz.


As the magnet gets farther away the amount of lines being cut is less so the voltage gets less. THe north pole has a peak one direction and the south has a peak in the other.

I knew BC would get my humor.

Thank you. Do most US generating plants have 3 phase generators?

^^^X2

All a generator does is convert the rotational energy of the turbine to electricity.

3 phase is the most effiecent means of generation,Because it takes the same energy to spin the turbine whether there is a single magnet or 3 on the rotor.