Toros
Senior Member
- Location
- Tujunga, CA
hi
Where Do I get C & Z-value of copper for 3 phase voltage drop calc???
Thank you
Where Do I get C & Z-value of copper for 3 phase voltage drop calc???
Thank you
C & Z Value
- Thread starter Toros
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the NEC has a properties table with X, R and Z (at pf 0.85 and 60 Hz iirc)
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
What is C value?
Conductance? That would be G with a unit of S.
Conductance? That would be G with a unit of S.
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
Wait, are you using C for the constant instead of K?
jumper
Senior Member
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- 3 Hr 2 Min from Winged Horses
Okay maybe I am overthinking this.
C is also used for Capaitance and Celsius.
If it is C as in figuring Xc for Z, then see note 2, table 9. Xc is not used in the table calcs.
If it is C as in using a different temperature (usually denoted as T) than 75C, then see note 2, table 8.
C is also used for Capaitance and Celsius.
If it is C as in figuring Xc for Z, then see note 2, table 9. Xc is not used in the table calcs.
If it is C as in using a different temperature (usually denoted as T) than 75C, then see note 2, table 8.
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
Anyone ever feel like you are talking to yourself?
My dear wife does it all the time..........Anyone ever feel like you are talking to yourself?
Maybe the OP will explain what C he is referring to.
For voltage drop one would normally refer to R and Z.
But what would I know - I'm just thick according to..................you know who.
Anyone ever feel like you are talking to yourself?
not an issue
now answering is another matter
jumper
Senior Member
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- 3 Hr 2 Min from Winged Horses
I will need to discuss this with the other three voices in my head before I can properly address this......
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- Placerville, CA, USA
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- Retired PV System Designer
"If I wanted your opinion, dear, I would have told you what it is."
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Toros
Senior Member
- Location
- Tujunga, CA
C-value attached
C-value attached
What does the c-value mean here
Area of a conductor, circular mils ???
see attached
Thank you
Ed:happysad:
C-value attached
What does the c-value mean here
Area of a conductor, circular mils ???
see attached
Thank you
Ed:happysad:
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
That chart is not VD.The bottom one is.
No, C there is some constant (non-changing variable) used for a short circuit calculation, Isc.
I have no clue what it stands for or how it is derived. It is not total circular mils however.
That is an EE level calc for the most part, I have never did it.
Here is a good link with math and charts if you are interested.
http://www.cooperindustries.com/con...rary/BUS_Ele_Tech_Lib_Electrical_Formulas.pdf
gadfly56
Senior Member
- Location
- New Jersey
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- Professional Engineer, Fire & Life Safety
I do that from time to time when working through a problem. Had a supervisor who sat in the cubicle on the other side of the "wall" from me quip, "Talking to yourself again?" Un-sotte voce I replied "absent-mindedly", "Sometimes it's the only way I can have an intelligent conversation around here." Our executive admin heard the whole exchange and collapsed in hysterical laughter when I followed that by saying all innocent-like: "Did I say that out loud?"
MyCleveland
Senior Member
- Location
- Cleveland, Ohio
TOROS
Refer to page 6 of 10 on LINK provided by "JUMPER".
C - constant values used in the Point-to-Point calculation method.
PDF has ALL the formulas used depending on 3P-1P-etc.
Keep a copy, you can put the formulas into a spreadsheet and calc your own results as needed.
The VD drop calcs on the PDF you provided I believe are incorrect.
Listing a Z value from Chap 9-Table 9, which is calculated at PF=0.85.
Formula on PDF seems to be adding another factor of 0.8...not sure where this is coming from.
Z values in your PDF tables are NOT the Z values from NEC except for the #4/0.
Refer to page 6 of 10 on LINK provided by "JUMPER".
C - constant values used in the Point-to-Point calculation method.
PDF has ALL the formulas used depending on 3P-1P-etc.
Keep a copy, you can put the formulas into a spreadsheet and calc your own results as needed.
The VD drop calcs on the PDF you provided I believe are incorrect.
Listing a Z value from Chap 9-Table 9, which is calculated at PF=0.85.
Formula on PDF seems to be adding another factor of 0.8...not sure where this is coming from.
Z values in your PDF tables are NOT the Z values from NEC except for the #4/0.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
Did anyone else notice that they spelled “fault” incorrectly on that chart? My brain can’t avoid seeing things like that, sometimes I get tired of it because I get stuck on it.
A lot of that happens. Here and elsewhere. It irks me too (or two or to) but I try to let it go under the radar as long as the intended meaning is clear. There are bigger things to worry about.
Toros
Senior Member
- Location
- Tujunga, CA
thank you,
just corrected
imho that method is confusing and more complicated than necessary
just do a single line with the Z for each xfmr/wire segment
can be modified from infinite bus to util supplied values by reflecting util Z to sec
easy to make an excel spreadsheet
MyCleveland
Senior Member
- Location
- Cleveland, Ohio
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
It may be, I cannot say either way.
While the actual math is pretty basic, IME it has always been an EE or Senior EC who performs it. I have never been asked to do it.
I can say that from experience that screwing up and installing 10k equipment when 22k stuff should have been speced cost my boss a pretty penny to replace a pile of discos and panels and such.
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