Electrical Wiring in the Home/wiring


QUESTION: I have four 250mm cables connected paralell to supply power for line 1 in a three phase 440volt circuit, the cables are not sharing the current equally. Why does this happen?

How unequally?
What are the readings for the 4 conductors?

[an error occurred while processing this directive]---------- FOLLOW-UP ----------

QUESTION: 1. The other phases has the same problem.
2. One cable carries 45% of the load and the other 3 shares the remaining 55% of the load. Note. Load is 1300amps, voltage 442volts and frequency is 60hz.
3. what reading of the 4 conductors are you referring to is it the resistance or voltage?

Appreciate any help

ANSWER: Not enough information
How are the cables installed?
What reading would I need except the current? It was what you referenced!
You are saying one has 585 amps and each of the other three has 238 amps
How are the conductors installed?
Cable tray? Conduit? I can't read your mind and I can't see your job
Did this just start? or is this a new installation and it has the problem?

There are two obvious probable causes. The 4 conductors in each phase are of different lengths [you need to cut them all the same length then install them and leave them the same]
There is something wrong with the termination of several of the conductors.

Did you use the same wire for all conductors of the same phase? Is one copper and the others aluminum?
How sure are you that they are all the same size?

---------- FOLLOW-UP ----------

Layout of the Wires
Layout of the Wires  
QUESTION: Thank you for you reply. We really appreciate the help. Your answers are proving to be very helpful.

The cables are installed in cable trays.The run on a flat surface side by side. This cable connect the main supply from the 3 phase main switch to a 2000amps ATS (Automatic Transfer Switch). The are all the same type, size and made from copper (all were cut from the same roll).
For the wire termination we use lug terminal that suit both application i.e. copper and aluminium as per the wiring regulation.
There is a difference in the cable length; about 2-3ft. This is because of the angle for the end connection see picture attached.

Guess I won't be much help.
Looking at the pictures, you have at least a 140 foot [40 meter] run. Those values just don't make any sense mathematically. The one conductor would have to be half as long as the other three....and to have it happen in all three phases is odd beyond mention.

This is a link to one of several discussions about this with a formula based on cable length:

I would be VERY interested to hear if you find the answer to your problem.

email - robert@wilberelectrical.com
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Robert Wilber


Licensed Philadelphia electrician serving Delaware, Chester, Montgomery and Philadelphia County in Pennsylvania. I install and repair residential, commercial and industrial wiring and lighting. Troubleshooting and repair of problems that stump other people is my favorite. I am willing to help people figure out why things don`t work. I understand motor controls, transformers and machine wiring. I do not teach basics to novices or do free design work.


Experience in the area I have 44 years experience in residential, commercial and industrial electrical construction and repair, 480 volts and below. This is not to be confused with one week repeated two thousand times.

44 years experience in residential, commercial and industrial electrical construction and repair

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