hi all,

According to the manual, this inverter can "bypass" from grid to AC loads.  Does anyone know more about how this 'bypass' is achieved.  I am told that the max bypass power is the same as the inverter rating - 5kW.  I would normally assume that the bypass functionality is achieved via some form of contactor.  If this is the case, why would Kodak limit the bypass power output to 5kW?

Secondly, in the attached snippet from the Kodak OG Manual, it says : "If “SUB” (solar first) is selected as output source priority and solar energy is not sufficient to provide the load, solar energy and the utility will provide the loads and charge the battery at the same time."

My understanding of this, is that the utility AND the solar energy (being the DC to AC hexagon) will be combined to support the AC loads.  But I am told by the representatives that its either the utility OR the inverter which supplies the AC loads.  So effectively, the inverter cannot synchronise with the utility.  Does this sound correct? 

 

22 hours ago, ryanb said:

I would normally assume that the bypass functionality is achieved via some form of contactor.  If this is the case, why would Kodak limit the bypass power output to 5kW?

It's a relay, rated at 40 A in most 5 kVA models, so it should be good for around 9 kVA, assuming that the AC-in and AC-out wiring is rated for 40 A.

I've just checked Axpert VM III firmware version 20.59 (because it's the one I've commented the best), and it seems to use rated power as the criterion for initiating fault code 07, overload timeout. So that's 110% of RATED output for 10.5 seconds, 150% overload for 5.5 seconds, or 200% overload for 200 ms. If the mains voltage is less than 170 VAC, then the limit could even be lower than the rated power (only 50% of rated power at 90 VAC, and a straight line between 50 and 100% for 90 to 170 VAC respectively).

Why do they do this? I suspect it's to do with the thickness of the PCB tracks that have to carry this current between beefy terminals and the relays.

22 hours ago, ryanb said:

My understanding of this, is that the utility AND the solar energy (being the DC to AC hexagon) will be combined to support the AC loads.

I believe that this is correct, for SUB output source priority at least.

22 hours ago, ryanb said:

But I am told by the representatives that its either the utility OR the inverter which supplies the AC loads.

That is true for the Axpert MKS models, but not for any model with SUB output source priority (Kings and those with ≥ 400 V max PV voltage).

22 hours ago, ryanb said:

So effectively, the inverter cannot synchronise with the utility.  Does this sound correct? 

This is not correct. ALL Axpert models synchronise between AC-in (when present and of suitable quality, i.e. the AC-in icon is on solid, not off or flashing), even if this is only to make the switching of loads between between AC-in and inverter output less brutal.

On 2022/06/30 at 3:33 PM, ryanb said:

solar energy and the utility will provide the loads and charge the battery at the same time

Maybe I'm getting into semantics here, but is it possible to charge and discharge (create ac-out) the battery at the same time?

9 hours ago, jumper said:

is it possible to charge and discharge (create ac-out) the battery at the same time?

When the battery is charging from utility, the DC-DC converter (battery to bus) is operating in reverse (bus to battery). Load power can come from the inverter (PV to bus to load) and/or from utility. If the PV isn't sufficient to power the load and charge the battery, part of the load power and will be from utility. If the PV power isn't enough to charge the battery, the inverter will also operate in reverse (AC-out (= AC-in in this configuration) to bus.

But you can't charge and discharge the battery at the same time; that doesn't make sense. The inverter input is the DC bus, which doesn't have to come from the battery, it can come from PV (in this model).

2 hours ago, Coulomb said:

But you can't charge and discharge the battery at the same time; that doesn't make sense.

That's exactly what I was thinking which is why I was wondering how it would be possible for the battery to provide AC loads if it was being charged by AC-in, but as you say it can come directly from the PV via the bus, thanks for the explanation. Just thought there might be something lost in translation.

On 2022/07/02 at 11:57 AM, Coulomb said:

When the battery is charging from utility, the DC-DC converter (battery to bus) is operating in reverse (bus to battery). Load power can come from the inverter (PV to bus to load) and/or from utility. If the PV isn't sufficient to power the load and charge the battery, part of the load power and will be from utility. If the PV power isn't enough to charge the battery, the inverter will also operate in reverse (AC-out (= AC-in in this configuration) to bus.

But you can't charge and discharge the battery at the same time; that doesn't make sense. The inverter input is the DC bus, which doesn't have to come from the battery, it can come from PV (in this model).

Hello.
I apologize for the strange question. But I correctly understood that the circuit that I tried to depict is not possible? Let me explain why, I do not have a stable city voltage and I would always like to receive 230v.
I use Max 11kw.

7 hours ago, sergeyshadow said:

But I correctly understood that the circuit that I tried to depict is not possible? Let me explain why, I do not have a stable city voltage and I would always like to receive 230v.

You are correct in that your MAX can't do what you want, which is called double conversion. Voltronic do make two models that do this; the Axpert King 1 and the Axpert King II. Since your panels are wired for high voltage, you could replace your MAX with two Axpert King IIs in parallel. It will convert incoming unstable AC power to DC (the ~400 VDC bus, not the 48 V battery), then convert it again to a stable 230 VAC (or 220 V or 240 V if you want). You lose a little efficiency with the double conversion, that's why most models don't have this feature. I believe that the Kings are designed for this scenario (poor utility voltage), though there is also the advantage of zero transfer time, for loads like auto teller machines that mustn't have interrupted power, even for 10 or 20 milliseconds.