question

raul-v avatar image
raul-v asked

discrepancies in cable section recommedations among victron manuals

I just upscaled to a phoenix smartsolar 12/1600 VA inverter.

English manual recommends to use 70 mm2 cabling

Spanish manual recommends to use 50 mm2 cable


70-mm2.jpeg

50-mm2.jpeg

My understanding is that 50 mm2 cables may stand up to 134 A and 70 mm2 171 A when ventilated what in either case does not seem enough for the maximun 3000 V at 12 V.

I understand that maximum time at peak power is around 0.5 seconds? even considering a power factor of 0.8 means 3000 VA/ 12 V gives the 250 amp fuse?

The purpose of the fuse is to protect the cable or the inverter or Both?

I´ve researched the kind of time reaction curve that the mega fuses have (even in victrons datasheet) but dont have it very clear.

I cant evaluate if a 50 mm2 cables in a 1.5 m lenght will be adequate enough or energy losses and overheating will became a potential risk?




Phoenix Inverter
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50-mm2.jpeg (1013.5 KiB)
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dognose avatar image dognose commented ·

According to some calculators, running 250A through a 1.5m 50mm² will result in 2.23% loss. (70mm² would be 1.59% and 90mm² would be 1.24%)

Fusing that with 250A is way to much, that fuse will never open in a timely manner.

If you take a look at this "mega fuse" datasheet, A 125A Fuse operated at 200% will last between 1 and 15 seconds. (Time/Current Characteristics top right)

https://m.littelfuse.com/~/media/automotive/datasheets/fuses/passenger-car-and-commercial-vehicle/bolt-down-fuses/littelfuse_mega_datasheet.pdf

Given you want to allow some "peak" currents, but generally operate with the inverters continuous power of ~ 1300W, i'd take a 125A Fuse. (Running at 135%, so 168 Amps, it will still allow that for 120 - 1800 seconds)

If you notice that fuse getting destroyed to often, you could increase it's rating. But starting with a 250A right away may just lead to issues, because it will allow 300A or more for way to long.

Better blow some fuses and increase them step-by-step than starting "to big" and toast your wires ;-)

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2 Answers
Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

Hi @Raul V,

It’s such a big topic that we have written a whole book about it

https://www.victronenergy.com/upload/documents/The_Wiring_Unlimited_book/43562-Wiring_Unlimited-pdf-en.pdf

If you still have questions after reading that let me know and we can go over what else is missing.

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raul-v avatar image
raul-v answered ·

Thanks a lot, ill go over it.

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