pudge565

I disagree with you. The wording that you quoted refers to the way it is identified not the color to be used. "...shall be durably and permanently marked by an outer finish that is orange in color or by other effective means..." The "...or by other effective means is saying that the insulation covering does not have to be orange in color it can be re-identified as orange in color (if allowed by other sections of the code) but it shall be orange in color.

Bob Badger

And I disagree with your disagreement.

Other effective means could simply be tags or and other way acceptable to the AHJ.

pudge565

Duly noted. I suppose it is up to the way the AHJ interprets it.

Mogie

I know this is an old post, but I don't think anyone ever answered your question. Voltage between phases is not necessarily additive. In a delta service, A-B=240v; B-C=240v; A-C=240v. You derive 120v on A and C phase by grounding between the two 120v coils in the center. The voltage from ground to B is then as shown in oldman's diagram, resulting in a nominal voltage of approx 208 (often anywhere between 200-210).
In a 120/208 wye service, ground is derived in the center of the "Y", resulting in 120v from ground to each of the three phases, making it a more useful transformer configuration for commercial applications, where minimal motor loads are used. Voltage between phases is then calculated by 120v x 1.732 (square root of 3) = 208v nominal. Similarly, w/a 480v wye configuration, ground is established in the center of the "Y". Ground to each phase is 277v. Phase-to-phase voltage is calculated as 277x1.732 = 480v.
I hope this clears things up a little.

kwired

Drawing out a delta connection or a wye connection make your coils 120, 240,208, 277, or 480 units(mm, inches, feet, miles whatever you wish) that apply and you will find that geometric rules will define the size of what you draw. If you draw a wye with 120 long legs that are 120 degrees apart the ends will be 208 units away from each other. Now think of the units of length as a number of turns in the transformer coils and equate this to the voltage produced by that number of coils.

Same thing applies to straight lines representing single phase transformers - a tap in the center will be half the distance of the line, a tap in the center of a coil will be half the voltage to each end as the voltage is from end to end.

Avanti

There are many types of delta transformer (TX) connections ether single phase or three phase. On a single phase transformer the most common type is the Wye high side and delta secondary side 120/240v the result. Three phase however is a different story, well we don't even need three high side (Primary or H1) phases. The open WYE/ DELTA can be used to make two 120v legs and light three phase secondary power from only two Primary phases and two Wye / Delta single phase TX's. This is a common connection for small apartment buildings for the there phase elevator load. This connection produces three phase secondary 240V power; using one TX for lighting load and the other for the power load. By tyeing the X1 of the power TX to the X3 of the lighting TX making three phases, by using a full coil on the power Tx and on half a coil on the lighting TX. The result is 120V on all the secondary legs and 240v phase to phase on all except the X3 of the power TX will be 208v to ground However; the same X3 leg phase to phase will yield 240v phase to phase. The 208V is measured phase to ground and this voltage is a result of the delta connection. I know of nothing that uses 208v volts to ground in this country or else were. The 208. is pretty much useless except on trouble shooting problems as a voltage cheek. If I have 208V to ground on the power leg I know that both Tx's are hot to the high side. Note for this discussion I used two WYE / DELTA , additive polarity transformers. This is only one type of TX hook up there are many, wye /delta , open wye / delta , closed wye/ delta, closed delta/delta; and all are 120/240v or 240/480 as all delta secondary is. Grounded Wye 120/208v, 277/480v voltage is a hole other animal.

Avanti

I have seen orange and also purple used for the high leg. All three PoCo's i have worked for 32 years put the high leg on the far right position in the meter can, C phase have you, I know the NEC has it in the middle B phase. They do this because the 3 phase delta meter is set up to meter with the high leg to the right.

brian john

In my experience a secondary of a single phase transformer is neither delta or wye.

What do you mean by TX?

The open delta transformers I have seen if the 120 VAC is derived on the secondary 3 phase was not available for motor loads? Can you post a link or diagram?

Are you referring to a center tapped winding for the 120 VAC?


Actually lots of stuff utilizes 208 single phase grounded or ungrounded. That we do not use 208 in a 240 center tapped delta is a NEC rule. But the equipment itself could care less if one side is grounded.

And here I have no clue what you are trying to say. Could you explain further.

__________________
Brian John
Leesburg, VA

Avanti

Yes I can just what is in need of clarification?

kwired

Can you post a schematic of the "Wye-Delta" single phase transformer?

I have never seen a single phase transformer that was not a single winding high side and single winding low side, with possible taps for multiple voltages but essentially still one winding. They are supplied by conductors that are part of a three phase system at some point, unless you know of a power generation plant that only generates single phase power.

Avanti

I am new to on line posting and don't k now how to attach anything. Is there a guide somewhere so I can upload a image of a wye/delta.

KenK

Smaller conductors can be run, more efficient.

CheapCharlie

That made me laugh...good one. Robertson are the best screws around. Too bad US won't use anything invented in Canada. lol

ilikepez

I love Robertson screws. They also have an amazing story behind them.