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22nd Nov 2019 Login  
Re: How long Cable run?
by Bryan Rendall at 2008-10-26 18:19:17 (Forum::Public::Wind)
Hi Ted,

Minor flaw in your calcs here... The voltage drop is considered across the 3 phase AC cable, unless you have the rectifier at the turbine, which although possible, would be very unusual.

Most installations are likely to use a 3 core armoured PVC insulated cable, i.e. table 4D4B from BS7671. From this, you have more or less got the right values for 10 and 16mm2 cable. But when calculating the current, you need to bear in mind a couple of things. Firstly, the AC voltage is lower than the DC voltage (quirk of AC to DC rectification), and secondly, the line current is spread over the 3 conductors (but not simply by dividing by 3 but the square root of 3!). So the line current in each of the 3 conductors isn't simply a division of power (6000W) by nominal DC volts (300) which is how I assume you have come to 20A?

Any length of cable is possible - Its just that the size of it has to be calculated to be sufficient to the current, the original voltage at the supply end, and the distance.


--
Bryan Rendall

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How long Cable run? CL - 29/09
    Re: How long Cable run? Stuart - 29/09
    Re: How long Cable run? Colin - 29/09
       Re: How long Cable run? Simon Ridout - 29/09
    Re: How long Cable run? Ted Marynicz - 30/09
       Re: How long Cable run? CL - 30/09
          Re: How long Cable run? Stuart - 1/10
       Re: How long Cable run? Bryan Rendall - 26/10
          Re: How long Cable run? Ted Marynicz - 27/10
          Re: How long Cable run? Tony Smith - 27/10
    Re: How long Cable run? haydn jones - 13/11
    Re: How long Cable run? Bryan Rendall - 24/10
       Re: How long Cable run? There is an attachment here Peter - 25/10
          Re: How long Cable run? There is an attachment here Peter - 25/10
             Re: How long Cable run? Bryan Rendall - 25/10
                Re: How long Cable run? Peter - 25/10
                Re: How long Cable run? Peter - 25/10
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