×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Voltage drop Equation

Voltage drop Equation

Voltage drop Equation

(OP)
Which one of the following equation to be used for three phase voltage drop calculations. I believe the equation (1) is more accurate than (2). Why do some literature mentions the equation (2) to calculate voltage drop. Is equation (2) applicable for only for some restricted applications, if so what are the applications?

1)

or

2)

RE: Voltage drop Equation

The no.1 it is more accurate than no.2, in any way.
However, if a.c.R/X>=7 the error will be less than 1%[as for copper conductor cross section area less than #4]
By the way,there is a more accurate formula for voltage drop [See IEEE 141/1993 3.11 Calculation of voltage drops]

RE: Voltage drop Equation

(OP)
On reading further, another equation is,

VD = (mV/A/mtr x length x Current x PF)/1000

RE: Voltage drop Equation

If you intend to follow BS7671 Appendix 4 chapter 6 TABLES OF VOLTAGE DROP, at first this formula it is for cross section less than 16 mm^2. For more than 16 mm^2 the
recommended equation it is close to your no.1.
However a factor Ct [very sophisticate in my opinion] has to be employed as temperature correction factor.
Then, for cable cross section area of 16 mm^2 or less:
VD=Ct*cos(Φ)*[mV/A/m]/1000 [V] and for more than 16 mm^2:
VD=Ct*[mVr/A/m*cos(Φ)+mVx/A/m*sin(Φ)]/1000 [V]
Of course for single phase system you have to multiply by 2 [forward and backward] and for three-phase by √3 ≈1.73.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources