Solar Pv A.c Cable Sizing...

[johnsimm]

I am currently installing a 18Kw 3 phase system.

The system has 3 strings of 25

Each panel has an output of 250W

The size of the AC cable on the spec is specified as 25mm from the AC isolator to the 3 Phase MCB.

If my calculations are correct..

18000/(√3x400) = 18000/1.732x400 = 18000/692.8 = 25A ( minus power factor ) 

So 25A per phase ? 

Meaning a 6mm cable would be sufficient?

Any input would be of much help ... Thanks alot guys 

 

[Andy™]

there is a lot more to cable choice than simply current capacity. maybe the person who spec'd the job has done it correctly taking other factors such as length, volt drop etc...

 

[kme]

#homework?

 

[johnsimm]

the cable is a meter long lol! don't think volts drop is worth my hassle Thank you for the great help though ... p.s work for a MCS accredited company and someone will be checking my work but was just a question.

 

[binky]

1m meter from inverter to Dist Board? Answer to your question is that it is basic AC cable calculation, bar volt drop should be 1%. Would be worth looking at Doncaster cables calculation tool, depending which cable you chose, the size will vary significantly, though at 1m a bit of 2.5 would probably do :innocent

 

[Sidewinder]

Probably sized to be the same as the main tails?

 

[KhaledElsheref]

No,, I don't think a 6mm thick cable would be sufficient.

 

[Blue Duck]

Why!

 

[Blue Duck]

Thanks Canoe!

As I understand 6mm over 1m would be sufficient. In fact...



Multicore 90°C Armoured Thermosetting Insulated Cables

Tables Apply to: H6942XL, H6943XL, H6944XL, H6945XL, Tuff Sheath,

Voltage: 230V

Load: 5.75kW / 25A

Length: 1m

Method of Installation: Clipped direct

Cable Size: 1.5mm²

So I was questioning why 6mm would not be sufficient?

 

[binky]

and what size is the neutral????

Cable size vares enormously with cable type. In theory the inverter output is balanced making neutral fairly irrelevent, any loss of a phase should shut the inverter down, so in theory Neutral can be ignored.