2.1 kWh inductive load causing problems

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logic28 asked May 21, '24

2.1 kWh inductive load causing problems

Now, here’s something that makes me wonder:

I’ve been drawing up to 7 kWh from my Victron twin Multi 5k and 20k battery storage with no problems for months now and the only item that will cause a system cut-off is my larger Hydrovane Compressor out of two.

The smaller one’s motor is rated 1.1kWh and never gave me problems even when I only had one Multiplus installed and, tested yesterday, it draws 16A as rush current and 8.5 A once running.

The larger motor is rated 2.2kWh and draws 25A at start and 17 A in normal operation.

When I only had a 5K battery and one Multiplus it would not even start without halting the system, not even with a soft start installed however now with 20k storage and two Multi in parallel, it only runs for about 40 seconds before the same problem occurs shutting down the main relay.

How can that be? The readings don’t lie and if it takes 25A to start with no problems why should it halt the system with only 17A after a short period of time?

It runs perfectly from the grid.

I get the typical message “L1 Overload” & “Battery low” but when I check the voltage in VRM it is never outside the normal range.

All cables are of the correct size, 50mm for the 5k battery and 70mm for the 15k, 70mm for both Multi and 30mm for the two MPPTs.

No loose connections or battery busbars, the larger battery has an 180A Eaton fuse.

Lynx shunt and distributor Multiplus fuses are genuine Victron 325 & 200A and I have installed auxiliary generic 100 + 200A Mega fuses in the Power In which are the only unknown quantity.

My question is, within the complex mixture of settings amongst Links, Battery, Multi etc. . . have I missed one that could cause this major problem?

The images show only - 11.3A and -18A at the time of the tests with a steady voltage of around 55/56 v at the VE bus.

vrm alarm

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Answer 1 · 2024-05-21T20:08:53Z

snoobler answered · May 21 at 08:08 PM

kWh is a measure of energy, i.e., kW use for h, hours. At times it's not clear what you mean. When discussing power, it's W or kW, no "h". Sometimes, you just use "K", so there's that too.

You are reporting only about 1.5-2X surge on your motors. Most motors have closer to 4-5X surge.

Actually, readings can lie. If you are measuring with a MAX function on an ammeter, it's not adequate. You need to use an ammeter specifically with an INRUSH function.

If you're really observing 2X surge vs. run on an INRUSH meter, I question the results unless you have a soft start installed.

VRM only logs at intervals of 1m or longer. If you enable display min/max, it may capture the minimum. You need to observe voltage on a BMV/Smartshunt on VictronConnect Trends tab where it updates about every second for a better idea of what's happening on a short term basis.

Are your inverters properly wired in parallel with equal length/gauge conductors? If one is forced to bear more of the load due to wiring, you can overload it.

Are your batteries wired properly such that both inverters share loads with the battery elements equally?

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logic28 commented · May 22 at 01:04 PM

 kWh is a measure of energy, i.e., kW use for h, hours. At times it's not clear what you mean. When discussing power, it's W or kW, no "h". Sometimes, you just use "K", so there's that too.

I always meant kWh as I started using it at the beginning of the thread so that the reader knows what I'm referring to, eventually, I used the shorter version of kW or K for short as I've seen done so many times in many discussions

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logic28 commented · May 22 at 01:08 PM

You are reporting only about 1.5-2X surge on your motors. Most motors have closer to 4-5X surge. Actually, readings can lie. If you are measuring with a MAX function on an ammeter, it's not adequate. You need to use an ammeter specifically with an INRUSH function.

I used a clamp ammeter for this test as that's all I have at present, however, as I said earlier, the problem now is no longer on startup but about half a minute or more after which is why I'm puzzled.

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logic28 commented · May 22 at 01:11 PM

If you're really observing 2X surge vs. run on an INRUSH meter, I question the results unless you have a soft start installed.

There is no soft start now, that was used when I only had one inverter but it didn't do much anyway.

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logic28 commented · May 22 at 01:35 PM

VRM only logs at intervals of 1m or longer. If you enable display min/max, it may capture the minimum. You need to observe voltage on a BMV/Smartshunt on VictronConnect Trends tab where it updates about every second for a better idea of what's happening on a short term basis.

Here are the Lynx readings at the times of the events, I still cannot observe any substantial variation in the voltage there and it shows 14.6A and 4.2A being drawn.

Instead, I can see a visible drop at time 07:47 with a 64.10A discharge but no alarm was raised even though I was using both resistive and inductive loads while preparing breakfast

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logic28 commented · May 22 at 01:43 PM

You are reporting only about 1.5-2X surge on your motors. Most motors have closer to 4-5X surge.

Actually, I didn't, I reported 25A at startup and 17A when running which is consistent with your statement being 5.75 kWh starting and 3.91 kWh running. Having said that the motor is rated 2.1kWh but it seems to be using much more.

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Duivert NL logic28 commented · May 22 at 01:49 PM

what is the Pf (powerfactor) of the motor?

if its bad current adds up fast

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logic28 Duivert NL commented · May 22 at 02:33 PM

what is the Pf (powerfactor) of the motor?

I have no access to the information but from what I can gather from the amperage it can not be more than 0.75 if that, whereas the smaller Hydrovane is marked as PF 0.88.

In any case, as I stated, I have had no issues with a much larger amperage being drawn having loaded the system with up to 7.5kWh with no alarms

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Duivert NL logic28 commented · May 22 at 02:48 PM

you cant measure Pf with a amp clamp meter ...

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logic28 commented · May 22 at 02:00 PM

Are your inverters properly wired in parallel with equal length/gauge conductors? If one is forced to bear more of the load due to wiring, you can overload it.

All the AC cables are perfectly balanced but I must say that the DC side from the Distributor to the Inverters is marginally different in fact was supposed to rectify that if any noticeable problem arose during heavy loads but, as we can see from the above image no alarm is activated even with a 60 plus Amps.

I did some tests on the DC lines some time ago and the amperage through both lines was reasonably even.

I might want to repeat the test using the compressor instead and see if it shows any difference in which case I'll replace the two shorter DC lines as I already have the new cable here.

The only problem is always been caused by the larger compressor motor from day one.

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logic28 commented · May 22 at 02:05 PM

Are your batteries wired properly such that both inverters share loads with the battery elements equally?

Yes, they both feed into the Power-In before going to the Lynx and the Distributor, the cables are balanced in length and the problem seems to be the same even running on one battery only.

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Answer 2 · 2024-05-22T16:05:22Z

snoobler answered · May 22 at 04:05 PM

Terminology doesn't matter until it does. There's no bad reason to use correct terminology.

Motors are not rated in kWh. They are rated in W or kW - a unit of power, not energy.

That clamp meter doesn't reliably measure surge. It does not have an INRUSH function.

Note that same brand model HP-6205. It specifically states an inrush function. So, this is a perfect example of readings that lie. I would trust the run currents, but your surge currents are MUCH higher.

Again, VRM may not reliably track rapid voltage changes. You can access the lynx shunt with VictronConnect through VRM.

You did report 1.5-2X surge vs. run:

The smaller one’s motor is rated 1.1kWh and never gave me problems even when I only had one Multiplus installed and, tested yesterday, it draws 16A as rush current and 8.5 A once running.

The larger motor is rated 2.2kWh and draws 25A at start and 17 A in normal operation.

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logic28 commented · May 22 at 06:22 PM

Thank you for your comments, and sorry for the misuse of kW and kWh

You did report a 1.5-2X surge vs. run:

I reported the Amperage during startup as being 25A which times 230V makes it 5250W not 1.5-2k, those fingers are the ratings of the two different motors as I said in the beginning.

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logic28 commented · May 22 at 06:35 PM

Note that same brand model HP-6205. It specifically states an inrush function. So, this is a perfect example of readings that lie. I would trust the run currents, but your surge currents are MUCH higher.

Again thank you for the tip, I have now ordered the HP-6205 so that I can better monitor inrush currents.

However, I'm not sure that the inrush current would persist for 3o/40 seconds like in my case or . . . would it?

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Answer 3 · 2024-05-22T20:39:40Z

sharpener answered · May 22 at 08:39 PM

The Multis have a short-term overload rating so will IIRC supply 100% overload for 30 secs. So after that time the overload capability steps down and if you are still drawing more than the rated current at that point it will trip, maybe that is what is happening. There is more detail in this webinar though the different overload ratings are a bit confusing as queried not very successfully in this thread.

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logic28 commented · May 22 at 09:31 PM

Thanks, I'll read the threads however in my case I cannot see this being a potential reason because, as I said earlier, I have been drawing twice as much for months without it tripping, this is only happening with the compressor's motor which only uses 17A after the initial 25A for start-up and it has no problem with that inrush current, only after a while. I suspect a problem with the motor but again it does not cause problems when running from the grid.

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