Load on AC-Input exceeds the limit under certain conditions, causing my generator to cut off

Question

question

tvidvei asked Aug 11, '20

Load on AC-Input exceeds the limit under certain conditions, causing my generator to cut off

At my summerhouse I have an off-grid setup with MultiPlus II 48 | 3000 | 35-32, 600W Solar panels, 2 x 4 LiFePo4 batteries (12V and 100Ah each) and a true sine inverter generator with capacity 1600W (240V x 6,67A). I have set a limit on the AC-Input to 6.0A to avoid overload on the generator. But still I experience that the generator is overloaded and cuts off. Of course, this happens most frequently when there ar sudden increases in the load when the generator runs and are swithched through, e.g. when we are running a washing machine. But it also happens when the load variations are minor: Changes in the size of 100W or even smaller can trigger such overload.

I expected that setting the limit on AC-Input would protect effectively against overloading the generator. With that limit set to 6.0A, I rarely see a load higher than 1300W from the generator in the Remote Console on LAN. It seems as if MultiPlus adds a margin to the limit an makes it even 10% lower, i.e 5.4A = 1296W in my case. I have even tried to set the margin to 4.0A, but still I experiences that the generator cuts off due to overloading, although more rarely. This is quite annoying as we can't trust that the generator supplies power to the system. We have to inspect the monitors and restart the generator many times if we try to use it when the load is not completely stable.

My question: How can I deal with this problem?

Multiplus-II Generator

2

2 |3000

Attachments: Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

fanda-eu commented · Dec 14, 2020 at 03:08 AM

I would like to add to this topic. My system is Quattro 8000 with 1600Watt inverter (running from an electric vehicle). For the simplicity however, I will call this external inverter a "generator"

Although it is clear that the generator can be overloaded when the load suddenly jumps, but I was able to work around this problem by setting the minimum accepted external AC voltage to a rather high value, so that the my generator is being "rejected" by the Victron rather instantly, before it is overloaded.

However one strange problem is that when there is a significant AC load - say above 1.5-2 kW, and the Victron attempts to connect the generator, on connect it will transfer the entire load onto the generator, ignoring the AC input current limit value, and despite the power assist feature activated.

Please note if the current load is not high - for example <1kW the Victron will smoothly transfer to the generator, with the current raising from 0 to the correct generator current limit.

Is there any way how this problem can be fixed ?

Victron Quattro runs the firmware v469

0 ·

JohnC ♦ fanda-eu commented · Dec 14, 2020 at 12:05 PM

@fanda_eu

Depending on your model Quattro, the minimum ac input limit that will be honoured is either 10.0 or 10.5 amps (with PowerAssist activated). This is beyond the rating of your 'generator'. You can set it lower by turning off PowerAssist, but you'll see the problem with doing that..

Your problem is really mismatched kit.

0 ·

Modifications Space

Node Red Space

Answer 1 · 2020-08-11T18:58:13Z

Jason Bolduc answered · Aug 11, 2020 at 06:58 PM

Hello,

When you say overload do you mean the generator engine stops or that a circuit breaker trips?

2

2 |3000

Attachments: Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

tvidvei commented · Aug 12, 2020 at 12:33 PM

I mean that a circuit breaker trips. It is the overload protection on the generator that is triggered so that no power is delivered. But the generator engine continue to run at a low speed as it does when there are no load.

0 ·

tvidvei tvidvei commented · Aug 12, 2020 at 12:43 PM

I wonder if the break is triggered by some "spikes" of high current that are not visible inside the VRM console, probably because the data in VRM are sampled by some some minutes intervals. But the generator accepts such spikes with at least 2.8 kW, which are created when I use it with my electric table saw. So currently I have no clear picture on what's going on.

0 ·

Answer 2 · 2020-08-12T22:16:05Z

Jason Bolduc answered · Aug 12, 2020 at 10:16 PM

The generator tripping of course heavily suggests transient surges are tripping your generator's breaker.

Victron's Powerassist is great - but it's not instant. When you are running off a generator the loads can surge the generator's power before the Victron equipment can start their powerassist.

In my off-grid setup I have used various sizes of generators. Our setup, 2 x 48v 5000w Multiplus, started having issues when we used generators below around the 7000w mark.

The unfortunate thing about generator sizing is that, for many setups, the best sizing of the generator that can handle surge loads is not the best sizing for charging batteries.

I run a 5kw generator durign the winter here. With that size I was still having trouble running large loads that used motors. This would sometimes result in the DC inductive loads "competing" with the generator resulting in tripped circuit breakers and wildly fluctuating AC voltage - not acceptable.

Due to the concerns over the AC power stability and quality I moved to a system where I charge the batteries from a system separate from the Victron multipluses.

Since I changed to a DC generator I am far happier. No flickering lights, no blown circuit breakers, no weird voltage changes. I think the idea of using inverter/chargers with AC generators is problematic. I have so much money invested in the Victron Multiplus and BoS gear I simply dont want to worry about damaging them from repeated "small generator" issues.

1

2 |3000

Attachments: Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

tvidvei commented · Aug 18, 2020 at 02:27 PM

Thank you very much for your answer. I see that these issues with generators and high transient surges have no straight forward solution.

Our fallback solution so far has been to run the generator only when no equipment that causes high and fluctuating loads (saws and other electric tools, washing machine etc) are connected. That works, although it puts some restrictions on when the generator can be run: Ideally, we would prefer to run the generator when other noisy machines are running, not when when everything else is quite and peaceful.

I have also tried to use voltage stabilizer (https://powerwalker.com/datasheets/AVR/PowerWalker%20AVR%202000%20SIV.pdf) betweent the Victron and the generator. I hoped that such equipment could "smooth out" the transient currents. I'm not quite sure of the effect. Still the circuit breaker on the generator is tripped, but may be less often.

I'll investigate your solution with charger separate from the Victron unit. Aside from the problem with overloading the generator, we also, by that solution, avoid that power from the generator is switched through directly to the loads. We just had to replace the main circuite board in our washing machine which was destroyed by the power from the generator.

0 ·

question