3 Phase Voltages

There is no such thing as 440/220V Y as a power line system voltage. There is 480/277Y, and there is 480 delta, and in some old systems there may still be 440V delta, but you are correct in that it would not be 440/220Y. Whomever you were having that conversation with was confusing a motor terminal wiring rating of 440-220V options with the utility supply options of 440 (again, really 480 now) or 220 (really

240) V delta. Truth is, the system voltage picture in the US is all over the map because many utilities were on their own and even competitive with their neighbors in the early days, so often they would have slightly different systems in a feeble attempt to keep customers on the fringes from switching.

Actually it was somewhat explained to me that 480 Y existed and that there were two windings per phase, so that 240 could be tapped middpoint of the phase, something along those lines. As well he described a numbering system illustrating 3 phases in 'Y' and starting from the top of say phase 'A' and proceeding in a clockwise direction and labelling the next phase 'B' , 2, and as well moving inwards towards the centre, marking the end of each winding with a number. (In all there was 12 numbers) Does this make sense, I mean is this some kind of standard.....?

David Grant

That could certainly be done, but I have never seen it. Why would any one customer need 2 three-phase voltages, especially those 2?

| A conversation recently came up in college about 3 phase voltages. More | specifically 3 phase voltage consisting of 600/347V (delta or wye) as | compared to 440/220V (delta or wye) It was mentioned that the second | voltage (440/220) came from somewhere in the east coast (US and Canada) and | here where I live and most of Canada it is 600/347 (industry) . How is this | voltage created ? I thought that the difference between phase and | neutral/ground was a factor of the Sq Rt. of 3 ( 347 * 1.73 = 600) So how | is 440 / 220 3 phase created / tapped ?

A more precise value for the square root of 3:

1.7320508075688772935274463415058723669428052538103806280558069794519330169088

There are quite a number of three phase combinations available, though not all are available in one place, normally. I'll list utilization (but not distribution) voltages I know about in the US from high to low:

1000Y/577 wye

This is primarily used in mining services, driving underground digging and drilling machines on very long "extension cords".

600 delta 575 delta (legacy voltage) 550 delta (legacy voltage)

Heavy industry. May exist in US, but I haven't seen it. Probably exists in Canada. I've seen transformers offered for this. This could come in open delta or closed delta.

600Y/346 wye 575Y/332 wye (legacy voltage) 550Y/318 wye (legacy voltage)

Industry and commercial, but with lower line-to-ground voltages. Rare in US (but I have seen it). Common in Canada. The lower voltage is commonly referenced as 347, but if you use and accurate square root of 3 to divide exactly 600, you get 346.41016151377 so the 346 is more technically correct. Using 1.73 gets you 347.

480 delta 460 delta (legacy voltage) 440 delta (legacy voltage)

Heavy industry. Still exists in US. This could come in open delta or closed delta. It may even come in center tapped for 240 volts.

480Y/277 wye 460Y/266 wye (legacy voltage) 440Y/254 wye (legacy voltage)

Industrial and commercial, but with lower line-to-ground voltages. Common in US, and generally available in Canada or much of North America.

433Y/250 wye

No one seemed to want this voltage, even though it works out nice and close mathematically :-)

416Y/240 wye 400Y/230 wye 380Y/220 wye

Not common in US, but apparently used by US military as lots of surplus generators have this voltage set up. Perhaps the intent was to work with a voltage more common in the world. I've seen this as an available voltage in one power company tariff.

240 delta 230 delta (legacy voltage) 220 delta (legacy voltage)

Still common in the US. Usually comes with a center tap on one winding that can supply a limited load of single phase 120 volts. It is usually stated as limited to 5% of total capacity, but I don't know if this means to total load on that one winding, or the imbalance between 120 volt loads on that tapped conductor.

240/208/120 tee 230/200/115 tee 220/190/110 tee

Similar to delta, and mostly compatible. But it is formed with only two transformers wired up at 90 degrees different voltages (one has the highest with the lowest as a center tap, and the other has the middle voltage and is known as "stinger" or "wild leg").

240Y/139 wye 230Y/133 wye (legacy voltage) 220Y/127 wye (legacy voltage) 216Y/125 wye (legacy voltage)

Available in a few place as a way to get lower line to ground voltages while being functional with 230/240 volt motors that can't make it down to 208. 220Y/127 is actually common in Mexico and works out quite close to the square root of 3.

208Y/120 wye 200Y/115 wye (legacy voltage) 190Y/110 wye (legacy voltage)

The most common three phase voltage in the US, supplying commercial and idustrial users, and in some cases residential.

120 delta

This has shown up in some places primarily in an open delta form. One such place is passenger railroad cars. It's entirely usable just like single phase 120 volts. But the line to line voltage is 120.

Six phase:

240*/208/120 star (theoretical)

You could build this with three center tapped 120/240 volt transformers bonding the 3 taps together. You'd get both 240 and 208 as needed. But I've never seen it used.

There has been some research into using higher order phases for distribution or transmission:

Single phase:

554/277 (theoretical)

Need to power 277 volt lighting w/o getting a three phase extension? You could construct this system to do it using the 277 volt transformers common for 480Y/277 systems, but connected on just single phase. I have never seen or heard of it actually being done.

480 240/480

Commonly used for roadway and tunnel lighting.

120/240

The most common service voltage in the US.

120 (2-wire)

Being "phased out".

60/120

Not really a service voltage, but can be a utilization voltage under NEC article 647 for low noise purposes like audio studios.

not a hero on this, just experience. it's really 460/277 and 208/120. the old references are generalizations of the basic voltages. sammmmm

| not a hero on this, just experience. | it's really 460/277 and 208/120. | the old references are generalizations of the basic voltages. | sammmmm

480 goes with 277. 460 goes with 266.

BTW, I've seen 240Y/139 listed as available in some power company tariffs. That's probably better for most of the 240 delta motors. You still need a separate supply for the lights, but three 240 to 120 step down transformers could do that for you, much as would be done with 480Y/277 using 480 to

120 (or 120/240) volt transformers.

I have seen what you are specifically talking about. It's the schematic of a motor that you can hook up 4 different ways. Wye high and low voltage and Delta high and low voltage. Say you have a motor wound with 6 different windings with 3 sets of pairs in phase with each other. On the terminal block of the motor which should have 12 terminals, you could hook the motor up in any of the following combinations for it to run on different voltages and would draw different currents. There are 6 windings which are accessed from the following terminals: Say each winding is rated at 120 volts.

Winding 1 is between terminals 1 and 4 (phase A). Winding 2 is between terminals 2 and 5 (phase B). Winding 3 is between terminals 3 and 6 (phase C). Winding 4 is between terminals 7 and 10 (phase A). Winding 5 is between terminals 8 and 11 (phase B). Winding 6 is between terminals 9 and 12 (phase C).

1. Connect terminals 4 to 7, 5 to 8, 6 to 9, 10 to 11 and 12. You could hook up 408v to terminals 1, 2 and 3. If you measured the voltage from the star point (10,11 or 12) to 1,2 or 3 you should see 240v (phase voltage) You could now run this motor on a line voltage of 408v. This is would be the high voltage hook up (series wye).

This is how it would look (change this font to courier)

| < winding 1 | < winding 4 winding 6 > / \ < winding 5 winding 3 > / \ < winding 2

1. Connect terminals 1 to 7, 4 to 10, 2 to 8, 5 to 11, 3 to 9, 6 to 12 and

10 to 11 and 12. You could now run this motor on 208v.(connect to terminals 1, 2 and 3) This is the low voltage wye hook up (parallel wye).

This is how it would look (change this font to courier)

|| // \\

1. Connect terminals 4 to 7, 10 to 2, 5 to 8, 11 to 3, 6 to 9 and 12 to 1. You can now run 240v to terminals 1, 2 and 3. This is the high voltage delta hook up (series delta).

This is how it would look (change this font to courier)

/\ / \ __ __

1. Connect terminals 1 to 7, 4 to 10, 2 to 8, 5 to 11, 3 to 9, 6 to 12, 10 to 2, 11 to 3, 12 to 1. You can run this motor on 120v. (connect yadda yadda...) This would be the low voltage delta hook up (parrallel delta).

This is how it would look (change this font to courier)

//\\

Kind of like what I just did there. It should be 408/240Y (not 220)...

you're right, i was generalising. i started in the forties. sammmm

transformers

Yes, I am certian I have heard of this as well. A 440 Delta, with something called a 'zigzag' tap.