RCD info?

[supersparky]

T1, I cannot say with any real certainty how they do the 3 inverters together, but I suspect it would be exactly the same as how they synchronise big three phase gensets to run in parellel. Now that is all done with a few very smart electronic control boxes. (sort of like your lithium charging controllers)
They do something called vector shift and when you think about it, it is all done in a fiftieth of a second. So it doesn't have to shift much.
Next time you get up this way I can take you somewhere and show you how they do it.

[Busman]

Thanks David,
Today local sparky installed 15 amp plug and 3 phase transfer switch, when I get time to move the current 2 inverters to the next bay and add the third we will make a large orange circular lead and change the single phase 15 amp plug. Only one phase wired through at present.
But for now we will have backup power for 3 fire fighting pumps, each on it's own tank, which was the object of the exercise.
Before then I have 600 vines to plant at the end of October, sheds to build for VP and the winery and still things to do for the house. And of course finish the irrigation for the vines and the windbreak trees.

[BruceS]

I think it's called retirement?
Most of us find we just don't have enough time to do things we want because we are sooooo busy!!

[jon_d]

So, the inverter linking kit to turn the output from 3 single phase inverters is just a timer for the 120* speration between phases, frequency matching and voltage matching, that sound about right? Does that mean each single phase requires its own neutral and the 3 phase plus neutral would have the neutral linked to all 3 single phase inverters?

Not quite.

There must be a master clock. And everything is referenced to that.
Otherwise any drift in frequency or phase will eventually lead to overlap.

[supersparky]

Busman, do you have any info on the magic box that ties all the inverters together. I would like to follow it up, for a completely different project that I have in mind.

[T1 Terry]

https://www.ebay.com.au/itm/15kw-Solar- ... 1ef3356f96 scroll down and they mention the parallel and 3 phase kits and show them connected up near the bottom

T1 Terry

[supersparky]

Thanks for that link T1.
It is exactly what I was looking for, to help a mate out. You have done all the legwork for me. Big thumbs up req'd

[T1 Terry]

OK, your turn, I need to be able to switch 450vdc between 2 different circuits. The drive/control side can be 10 -15vdc, 20-30vdc or 44 - 60vdc because I can tap off the 48vdc battery pack.
I'm looking to try to swap the solar feed between an off grid inverter and a grid tied inverter and the solar open circuit voltage is labelled as 438vdc @ 9.2 amps max current. The switching would be controlled by a cell voltage sensing relay output from the battery monitoring system.
The open circuit voltage or the max current don't add up using the specs from the panels they claim to have used. 10 x these Trina 250w panels http://static.trinasolar.com/sites/defa ... 05.08D.pdf Even as 270w panels the open circuit voltage 36.1v, x 10 is 361vdc not 438vdc and the Imp should be 9.3 amps for the 270w panels but only 8.9 amps for the 250w panels. Ya gotta wonder if these blokes even measure it or just stick a plate on that comes with every system no matter which panels are used.

T1 Terry

[jon_d]

Terry,

It needs to be a special switch. Otherwise, you'll get DC flash over and arcing.

btw, They're allowing about a 20% tolerance in the Voc

JD

[T1 Terry]

Terry,

It needs to be a special switch. Otherwise, you'll get DC flash over and arcing.

btw, They're allowing about a 20% tolerance in the Voc

JD

Fair enough Jon, would a solid state relay capable of that voltage and twice the current do the job? I'd need to use 2 relays, one to switch off the off grid and one to switch on the grid tie ...... or could I just use a Schottky diode capable of handling the voltage and twice the current? That way when the off grid relay opened or the solar control started to reduce the current flow so pushing the line voltage higher, the easier path would be through the diode. Would it even need to be a Schottky diode at that voltage but such low current?

T1 Terry