Transmission of 3phase output power of solar

kcbibek310kcbibek310 Registered Users Posts: 17 ✭✭
Hello,

I have a 3 phase pump of 17.5 Hp. And we are planning to install solar module of 15 KWp for the pump. Its rated current is 32.5 Amp. But the problem is the distance between the pump controller and the pump is about 830 meter. We are using vfd pump controller which locates near to solar module. Can anyone please help me to find the exact way of power transmission. Which type of wire should i use and what is the size of wire. I need this with calculation. So if anybody knows about it then please help me with this. 

Comments

  • BB.BB. Super Moderators Posts: 26,976 admin
    I am guessing you are in Nepal? And the motor is rated at 380-415 VAC (50 Hz)?

    And what is the rating of the VFD? Guessing, that it may be around ~565 VDC input minimum?

    In general, you want to send the highest voltage the longer distance (the 565 VDC Vmp-array voltage?). Also, VFD's (many times) may not like to send power down long cable runs (VFD's are usually some form of square or modified square wave, which can cause wiring to ring with the inductive load of the motor).

    Size of wire in US Gauge... If you want 3% voltage drop, with single phase (DC) wiring of 2,739 feet with an estimated current of (15,000 watts / 565 VDC =) 26.5 amps

    https://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=0.4066&voltage=565&phase=dc&noofconductor=1&distance=2379&distanceunit=feet&amperes=26.5&x=70&y=12
    1 AWG copper:
    Voltage drop: 15.63
    Voltage drop percentage: 2.77%
    Voltage at the end: 549.37

    https://www.calculator.net/voltage-drop-calculator.html?material=aluminum&wiresize=0.2557&voltage=565&phase=dc&noofconductor=1&distance=2379&distanceunit=feet&amperes=26.5&x=54&y=17
    2/0 Aluminum
    Voltage drop: 15.49
    Voltage drop percentage: 2.74%
    Voltage at the end: 549.51

    Of course that is in US measurements. In metric:

    G Number Ø [Inch] Ø [mm] Ø [mm²]
    6⁄0 = 000000 0.580 14.73 170.30
    5⁄0 = 00000 0.517 13.12 135.10
    4⁄0 = 0000 0.460 11.7 107
    3⁄0 = 000 0.410 10.4 85.0
    2⁄0 = 00 0.365 9.26 67.4
    1⁄0 = 0 0.325 8.25 53.5
    1 0.289 7.35 42.4
    2 0.258 6.54 33.6
    3 0.229 5.83 26.7
    4 0.204 5.19 21.1
    This is a very rough estimate--And lots of guesswork. I do not know what standards you have for wiring in your region, and if you will bury the cable, put the cable in conduit/pipe, or on poles.

    This is not a "trivial" installation... You need a power engineer familiar with your type of application and/or some help from the VFD company.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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