0
\$\begingroup\$

I have a single phase load (90 A 230 V) and 2 three phase loads (7 kW 400 V 3 phase/9 kW 400 V 3ph+N) connected at the same time to a three phase network.

How the 3 phase calculations (line current of each load, total line current) done in this case?

Are there any documents you recommend?

enter image description here

Obviously the single phase load draw 90 A from the line W.

For the three phase load 7 kW the current drawn by each line is:

I(U,V,W)= (7000)/(400*sqrt(3)*0.8) = 10 A

For the three phase load 9 kW the current drawn by each line is

I(U,V,W)= (9000)/(400*sqrt(3)*0.8) = 16.2 A

Total current drived by each line:

IU=10+16.2=26.2 A

IV=10+16.2= 26.2 A

IW=10+16.2+90= 116.2 A

\$\endgroup\$
4
  • \$\begingroup\$ Imagine the single phase load wasn't connected at all. Do you know how to do the 3-phase analysis? Then if only the single phase load were connected, do you know how to perform the single phase analysis? Please demonstrate that in your question. \$\endgroup\$
    – Andy aka
    Dec 14, 2022 at 21:04
  • \$\begingroup\$ (Why consider the three-phase loads separately? Where do you get PF from?) \$\endgroup\$
    – greybeard
    Dec 15, 2022 at 8:16
  • \$\begingroup\$ PF power factor = 0.8 \$\endgroup\$
    – Engineer
    Dec 15, 2022 at 12:18
  • \$\begingroup\$ (10 A / 7) * 9 ≠ 16.2 A \$\endgroup\$
    – greybeard
    Dec 15, 2022 at 21:34

1 Answer 1

0
\$\begingroup\$

You tried to use the power factor to turn the addition of currents into a scalar computation
(introducing an error with the 7 kW load).

Addition of AC load currents doesn't work this way even for linear/reactive ones.

I'd need to know whether current was leading or lagging voltage - for each load assumed uniform over all its phases.

Assuming the 3-phase loads either both capacitive or both inductive, the question remains underspecified in the single-phase load. (You can try to pull resistive/PF 1 out of thin air).

\$\endgroup\$
0

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.