calculation ?

[Smart $]

Actually, the "Y" is not optional. The 3ph, 4wire is optional, as it is redundant, since 208Y/120V as written means 3ph, 4W.

By the same token 3? 4W is redundant, so is "Y". Please describe a 3? 4W system having 208V line-to-line and 120V line-to-neutral that isn't a wye connected system...

...and if you stick to the convention that "Y" is not optional, why do you not write 240Δ/120 3? 4W, or something to signify a delta connected secondary?

I believe your only recourse is to state it is simply a matter of convention... and one which you subscribe to at that.

 

[kingpb]

The convention is stated quite clearly in IEEE C84.1 , Notes to Table 1. Whereby the "Y" is used to designate a 4 wire system. Delta connection as in 240/120V does not include additional notation, nor would simply stating 208V, which would designate 3ph, 3W. This is not to say however, that to avoid confusion, it might be prudent to use the 3ph/3W, or 3ph/4W notation, it's just deemed opional.

I speculate it is because a "Y" is a standard alphabetic character found on all keyboards, wheras a triangle symbol would be more difficult to duplicate from keyboards.

 

[Smart $]

I speculate it is because a "Y" is a standard alphabetic character found on all keyboards, wheras a triangle symbol would be more difficult to duplicate from keyboards.

True... but a "Y" is only slightly more indicative of the connection than writing say 240D/120V, where "D" is a standard keyboard character and would denote a Delta connected system.

I always "love" (sarcasm) so-called technical conventions which have little logic applied.

 

[charlie b]

Kingpb (and others): I am a Senior Member of the IEEE; I have been for nearly a decade. Nevertheless, and without regard to what the IEEE may have published on the subject of voltage system naming conventions, you are not going to break me, or a vast great deal of other people, of the conviction that "120/208" and "208/120" are synonymous, with or without including the "Y."

I do not believe it to be practical, for the purposes of the electrical trade, to distinguish single phase from three phase by use of the number that comes first in the sequence. It just isn't going to sell; not here anyway.

 

[kingpb]

Kingpb (and others): I am a Senior Member of the IEEE; I have been for nearly a decade. Nevertheless, and without regard to what the IEEE may have published on the subject of voltage system naming conventions, you are not going to break me, or a vast great deal of other people, of the conviction that "120/208" and "208/120" are synonymous, with or without including the "Y."

I do not believe it to be practical, for the purposes of the electrical trade, to distinguish single phase from three phase by use of the number that comes first in the sequence. It just isn't going to sell; not here anyway.

Charlie, you are more than welcome to incorrectly call it whatever you want, just keep in mind, if you use 120/208V on a drawing, don't try to tell the Contractor he was wrong for giving you a single phase service, and now wants an extra for providing a 3 phase service.

BTW: ...and I suppose you still call voltage transformers PT's instead of the IEEE dictionary supported, and correct designation "VT"?

 

[charlie b]

Not only that, but I also use the term "MCM," instead of "kcmil." "New" is not always better than "old," nor does "new" necessarily replace "old." What is important is clarity in communication.

By the way, I have other ways to convey to the contractor that the service is 3-phase, so I have no fear of a change order. I would be interested to find out if any contractor out there would price the job as single phase, if he or she saw "120/208" on a drawing.

 

[rattus]

Ok but the load is connected to say phase ?A? and phase ?B? the line to neutral voltage of each bus is 120V so would you not divide your load by two to split the load over the two busses and then divide by the line to neutral voltage of the panelboard to see the correct ampacity of the load?

Simply put: The load is not connected to the neutral, therefore the neutral does not figure into the calculation. This is just a load connected between two phases, therefore this SINGLE load sees 208V, and this voltage determines the current.

Draw out the schematics for each case, and the difference should be obvious.

 

[scott thompson]

ddubbs103

Just wondering if any one had any diagrams of services wye and delta etc? thanks!

Here is a link to the "Menu Page" at ECN, where you will find a whole bunch of Transformer Schematic drawings - some that you may have never heard of before, others that are commonly used.

Menu For Technical Reference Section

Be sure to search through both of the Links Pages in the Menu.
There are more than Transfomer Schematics at this link.

Scott

 

[ddubbs103]

thanks a lot for the replies, I always ask questions and half the time I get bullshit answers at work