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 Topic: Cable/Wire sizing AC/DC
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BarkyJ
Regular Member

Joined: 26 April 2018
Location: New Zealand
Online Status: Offline
Posts: 93
 Posted: 11 May 2018 at 10:28am | IP Logged
Hi All

Just doing some planning.
What is typically done for power cable from the windmill to whatever interface you guys use, and do you normally run 3 phase AC down the pole and rectify it at the ground, or rectify it on the windmill and run DC down the pole?

I found a good youtube clip which has an attached excel sheet for doing calculations which is quite useful.

https://www.youtube.com/watch?v=uS7CyTxAA4o

Based on this, my estimation whether I run AC or DC down the pole, I am in the region of requiring AWG 8 cable, which isnt cheap stuff.
My estimation so far is 15m one way, so 30m of cable (assuming DC 2 wire).

Curious what others are using and where you sourced the cable from.

Thanks

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BarkyJ
Regular Member

Joined: 26 April 2018
Location: New Zealand
Online Status: Offline
Posts: 93
 Posted: 11 May 2018 at 11:40am | IP Logged
http://www.nzev.co.nz/10mm-flexible-cable/

This is what I am currently looking at.
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Warpspeed
Guru

Joined: 09 August 2007
Location: Australia
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Posts: 1701
 Posted: 12 May 2018 at 10:42am | IP Logged
You do not say what your system voltage is, or the expected current.

Ten mm squared cable has a resistance of .00172 ohms per linear meter, so 30m of that cable will have a resistance of .0516 ohms (at 20 Celsius).

The "normal" current rating for 10mm cable is 50 amps.
I squared R gives a power loss of 129 watts at 50 amps for 30m of cable.
Voltage drop at 50 amps would be 2.58 volts.

I have no idea if those are significant figures for your intended application.

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Cheers, Tony.
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BarkyJ
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Joined: 26 April 2018
Location: New Zealand
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 Posted: 12 May 2018 at 3:03pm | IP Logged
Sorry the system voltage at this stage is 36V.
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Warpspeed
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Joined: 09 August 2007
Location: Australia
Online Status: Offline
Posts: 1701
 Posted: 12 May 2018 at 4:16pm | IP Logged
So its going to have about 7% loss at 50 amps.

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Cheers, Tony.
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