Long conductor sizing for motor

[triden55]

Never done this before as I am an electronics guy. Need to size an Aluminum conductor to feed a 3ph induction motor that is 550 meters (1800 feet) away. Motor is 600v and faceplate current says 85 amps. Power factor 80%. Allowed 5% voltage drop on the line. What size of conductor do I need? I did some preliminary calculations and came up with 3/0 but that seems too small for this long of a run.

Thanks,

Chris

 

[KllrWolf]

Is there a reason for aluminum over copper? With copper at a 5% max voltage drop is 2/0. I do know that aluminum cabling needs to be sized larger, but not sure by how much. Also for this length and low motor amperage, it is the voltage drop and not the current that is dictating the cable size in copper.

 

[waross]

A rule of thumb or a quick sanity check is two gauge sizes larger for aluminum. But always check the ampacity tables.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[PHovnanian]

Is there a reason for aluminum over copper?

That will depend on whether it is installed where copper thieves can get to it.

 

[KllrWolf]

Is there a reason for aluminum over copper?

That will depend on whether it is installed where copper thieves can get to it.

I did not think about that. Thieves for the cables to the motors we build would either need to be scuba diving pirates (ROV motors) or willing to pull the same length of pipe out of a hole (deep well submersible).

 

[dpc]

These crackheads would not notice if they were underwater or not.

 

[KllrWolf]

True, but the space between the piping and wall is only a few inches at best, the the ROV would either be on a ship or platform. Not sure they could swim that far.

Waross: Thanks for that rule of thumb. I will keep it in mind if I ever need to size aluminum wire.

 

[wareagle]

check this information first

http://findarticles.com/p/articles/mi_m0BPR/is_10_22/ai_n15766075/?tag=content;col1

 

[triden55]

Thanks for the info. I ended up going with 4/0 for the run. By my calculations, it should be under 5% voltage drop which will be a little nicer on the motor...