Re: PIP-5048GE, PIP-5048GK and PIP-5048MG inverters (with unsafe SCC)
Posted: Wed, 13 Feb 2019, 07:36
It would be great if we could always believe what these people say.
It seems reasonable to me that the solar charger would protect itself from drawing excessive current. Certainly, the low voltage models do. For example, I have 3200 W nominal PV power connected to my 3000 W nominal SCC, and have had no problems at all. But I may have been guilty of over-generalising from the low voltage models to the higher voltage models. These are buck and boost designs respectively. But I believe that in both designs, the active switching semiconductor only has to switch the output current.
Yes, but that's with one string. The charge circuit knew it was way under the current limit. With two strings, it would know that it was near the current limit, and would just adjust the PWM ratio to draw less current.As i said, most of the time is below that, but i saw it at 9,6 two times, specially after a cloud went away.
The only question is what happens with unintended surges. It certainly happens that when the charging circuit aims for a particular current, sometimes more than that current results, for a few seconds. But the current limit is presumably about heat dissipation, and can deal with a short term overload. It will be derating itself as its temperature increases anyway.
Yes, the voltage limit is a hard limit. Going over the switching device's limit even for a microsecond could cause avalanche currents to flow, which usually destroys the device immediately. The device's limit will have some margin above the 500 V rating, to allow for unavoidable electrical ringing, but you should certainly treat the voltage limit as a completely hard, never exceed limit. The worst case will be the coldest morning when the sun suddenly burts out behind a cloud.and also they told me no more than 10 in one string, as i will be over 500V DC.
Yes, except that the panels won't ever produce more than 18 A, because they are never loaded beyond the amount that would cause 18 A to flow. Think of a battery; most batteries are capable of many thousands of amps if a sufficient load (e.g. a short circuit) is applied. But under non-fault conditions, that sort of current never flows; you just get the current dictated by the load. The MPPT is a sort of variable load for the panels.If i understand properly, you say that Inverters will stop taking Amps form solar panels if it exceeds 18A, so he will work only up to 18A if it gets to , and if for some reason it goes to 19A it will refuse the extra 1A?
As mentioned earlier, no, over-voltage is a different situation.Same thing if i go over 500V DC? (which i find crazy scary by the way :):))
Again, no. The solar charger should never demand more than 18 A from the panels. The extra power from the sun goes to warming up the panels rather than converting to electricity. Think of a panel in the sun with nothing connected to it; where does the 9.5 A go? Nowhere, it never is generated, because a circuit isn't there for the current to flow through.So nothing should break down for sending 19Amps from the solar panels?
So to summarise again: I believe that you will be fine with the two strings, but this is based on my understanding of the buck-based low PV voltage models. I don't even see the 18 A limit in the specifications section of the user manual. (Have you found the 18 A figure in any catalog or specification page?) But you have to weigh my arguments against those from the supplier.
There is no effective way I can think of to limit the panel current to 18 A (wherever that figure came from).