# Transmission of 3phase output power of solar

kcbibek310
Registered Users Posts:

**21**✭✭
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.

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.

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## Comments

31,048adminAnd 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&eres=26.5&x=70&y=12

1 AWG copper:

Voltage drop:

15.63Voltage drop percentage:

2.77%Voltage at the end:

549.37https://www.calculator.net/voltage-drop-calculator.html?material=aluminum&wiresize=0.2557&voltage=565&phase=dc&noofconductor=1&distance=2379&distanceunit=feet&eres=26.5&x=54&y=17

2/0 Aluminum

Voltage drop:

15.49Voltage drop percentage:

2.74%Voltage at the end:

549.51Of course that is in US measurements. In metric:

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

29✭✭OK kcbiibk,

Here is a rundown for you.

15KW, 32.5 amp, 3p indicates you are using 337 volts.

830 meter = 2722 ft or approx 1/2 mile

Starting with an allowable voltage drop of 5%;

this allows 16 volt drop in the line.

At 32.5 amp this would be a total of 0.492 ohm or 0.181 ohm per 1000 ft.

But since the electricity must travel both ways we must half this value

giving an allowable conductor resistance of 0.091 ohm per 1000 ft.

This indicates 0 gage Cu wire or 00 Al wire to keep voltage drop below 5% at full power.

But 0 gage Cu is not a standard size.

Even if you could find it, it would be very expensive.

2 gage is readily available but would result in approx 8% voltage drop.

00 Cu (also available) would result in 4% voltage drop.

But because of the high price of Cu these jobs are usually done with Al.

A good choice would be 2 gage Al which would result in 7% voltage drop at full power.

Any decent 3p submerged motor will have no prob at 7% voltage drop.

I recommend the wire be buried.

This is the best lightning protection you can get.

The distributed capacity of a buried cable stops voltage spikes

and will tend to suppress any ringing.

There is no start up surge when using VFDs and 3p.

Set your ramp up for some 5 seconds and your start up current will be less than the run current.

Best wishes

29✭✭Just re-read the above post.

In the fourth paragraph second line,

it says 2 gage Al.

it should read 2 ought, or 00 Al.

Sorry abt that

21✭✭Can I get your email id, so that we can communicate further?