×
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

Parallel Conductor Impedances

Parallel Conductor Impedances

Parallel Conductor Impedances

(OP)
In the IEEE Buff Book (ANSI/IEEE std 242-1986) more specifically page 94, figure 21 shows the basic formula for calculating parallel impedance.

Z= (R1+jX1)*(R2+jX2)/(R1+jX1)+(R2+jX2)

If you substitute some simple whole numbers for the values such as r=2 and x=2 (for ease of calculation) the resulting impedance is

Z= 1/2 +j1

This illustrates that the resistance value is divided by the number of conductors (in this case 2) and the inductance value of 2 parallel cables is the inductance value of the one cable.

In the Buff Book on the next page 96, however, there appears a contradiction in the example where it shows the inductance value being divided by 2 for a paralleled cable.

I must be missing some basic understanding here. Can anyone explain the difference?

The basic question is: What do you do with the inductance value for paralleled cables?

RE: Parallel Conductor Impedances

Check your math, please.

For two parallel conductors of impedance (2+j2), I get a resultant of (1+j1), which matches the intuitive value of exactly half.

P.S. The last equation of Fig 21 is solved such that you don't have to manipulate any j^2 terms.

RE: Parallel Conductor Impedances

tinfoil is right

The correct impedance value is 1+j1

Parallel impedance is always calculated as the product over the sum of the two impedance values.

Z = (Z1*Z2)/(Z1+Z2)





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