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Limiter inverter with RS485 load setting
#42
(06-19-2020, 03:40 PM)Cell-King Wrote: Just to remind you, I have two inverter units and a meter box that is set to "2 Unit". They are connected with a twisted pair of a cat 6 cable that runs from the electricity supply box to my shed. One of the inverter units is daisy chained to the other for RS485 communication.

With the RS485 the cable may need a termination resistor adding depending on length of the cable. Read up on the reasons for termination resistors.

The sample values in hex appear to be only half of the packet showing only the first 4 bytes for a period of time and then showing a full packet. The dropouts occur at the 00 packet, which would make it look like the RS485 timings are out or a terminator resistor is needed on the line. How long is the cable run ?

The meter that is supplied with the unit I'm not impressed with, although I have 3 installed and they have been working ok without issue for quite a while. The CT's on them are split core and the only issue I have had is with them being not aligned fully which showed a lower reading. The worryign bit is that they are a plug because a CT left disconnected from a load will try and generate a massive voltage (because it is effectively a step up transformer) and then the CT wil effectively destroy itself through internal arcing. This is under a reasonable load passing through the cable it's clamped to.

The units themselves do seem to be ok once the RS485 data feed is clear and ok. My issue early on turned out to be the  adapters I was using making a mess of the packets, which still did not resolve 100% as I suspect that the units don't cope well with data packets that are not 100% reliable and the unit then sticks and holds whatever output it has.

I think the units have a timout on the packet reception, which is not long enough and it ends up merging received packets together, although again I'm only 20% convinced of this logic.

The meters are quite basic but the other odd aspect is with them the single unit selection outputs the data quite fast and then when you change it to 2 untis the meter only halves the reading output but for some reason (I think it is a failed attempt to manage the rate of change in load following) the update rate decreases. This is what conflicts with my initial thought about the packet timout creating issues.

The other element is that the output data from the units, which shows the voltage and curren, is pushed out onto the RS485 line seemingly at random and with multiple unit chained together they don't appear to have any way to syncronise the packet output and collisions do occur. This does not seem to impact the running appart from colliding with an update meter reading/settin. Ths again probably drops my 20% logic to 2%...

They can work ok....

Ahhh, another issue which you are yet to experience..... or not.

If you have this setup :

Mains Incomming --> CT --> Breaker box --> Inverter

Then the inverter will ramp up to full load when the power flows to export.

The reason is that the CT measurement does not register direction and therefore if you export 50W the inverter sees 50W "load" and outputs 50W which then results in 100W export and the inverter increases again, until this process ends up at full inverter output.

They have to be setup with the inverter output connected before the CT measurement point as per the diagram in the instructions.
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If you can't quantify how much they cost, it's a deal, I'll buy 5 of them for 3 lumps of rocking horse ......
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RE: Limiter inverter with RS485 load setting - by completelycharged - 06-19-2020, 04:17 PM

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