Hi guys

Am I correct if the manual states 
" Overload Protection / 5@> 150% ; 10s @110%~150% load"

Does imply that at 4 Kva unit it could handle a load of 6kv for 10 s MAX and higher for 5 sec max? The reason for asking is that the motor that I am looking at to "soft start" will give a max spike of 6 kw but it is just for a moment , looks like less than 2 sec. How bad is that for the Inverter?

Regards

Paul

6 hours ago, PaulF007 said:

Hi guys

Am I correct if the manual states 
" Overload Protection / 5@> 150% ; 10s @110%~150% load"

Does imply that at 4 Kva unit it could handle a load of 6kv for 10 s MAX and higher for 5 sec max?

I think it can handle >6 kVA for 5 seconds, and up to 6 kVA for 10 seconds. Is your load 6 kVA or 6 kW when starting? I think a 4 kVA inverter is specified to run 8 kVA for a short time.

I can't quickly find where this is done in the firmware, so I can't say what the exact limits are. But it sounds to me that your 4kVA inverter (3.2 kW continuous?) should just start that motor OK, assuming no other heavy loads at the time.

OffGridQld from the AEVA says his 5 kVA inverter is surprisingly good at starting large motors, like air compressors:

http://forums.aeva.asn.au/forum_posts.asp?TID=4332&PID=64077&title=pip4048ms-inverter#64077

6 hours ago, Coulomb said:

Is your load 6 kVA or 6 kW when starting?

Hi Coulomb

I quickly checked this morning. The start up load is 6 000 w and 6300 va - The highest that it has peaked was 6746 w and 7000 va . No load to it and is recorded for only a second or so. 

 

8 hours ago, PaulF007 said:

The highest that it has peaked was 6746 w and 7000 va .

`Ah. Then it's quite marginal, but I'd say it could do it. The other rating is "Surge Capacity:  2* rated power for 5 seconds". 2 x 3200 W rated is 6400 W peak. You don't need the surge for a full 5 seconds, so it's probably OK. The battery side MOSFETs, which are the ones that seem to blow most frequently, have a very high peak current rating, of 120 A each. There are 4 in parallel in the 5 kVA models, and I assume 3 in the 4 kVA models. So with some sharing mismatch, that's some 300 A at say 40 V under heavy load. That's 12 kW of peak power on the battery side, call it 10 kW at the AC output (and that's limited by the package; the silicon could take nearly twice that). So it looks like the limit is based on the ability to shed the heat, which means that short peak loads of less than a second duration could go beyond the 2 x rated power limit, assuming that the high currents didn't induce too much of a voltage spike in the only 75 V rated MOSFETs. Upgrading to 100 V MOSFETs, as suggested here, could be a good investment.

Edited February 27, 20178 yr by Coulomb
"12 kW of peak current capacity" -> "12 kW of peak power"

As a reference point, the Multiplus can handle 200% nominal for about a second.