On 9/11/2017 at 10:21 PM, pilotfish said:

Yes but you need something like 15 posts before you can download - swing around the forum and post under a couple of topics that interest you then head to downloads...

 Thank you pilotfish for your kind advice. I, have downloaded the Service Manual. From Google. Never the less, 

i would like to reach the 15 posts mark on this informative forum as you have suggested.

On 9/12/2017 at 1:01 AM, Coulomb said:

Actually, in the 4 kW Axperts, there are really only 2 modules, unless you count the processor daughter board as a third. The AC mains charger is actually the inverter run in reverse, so the power flow is from the AC input (connected to the AC output when AC charging) to the battery. In lower power models, I believe that there is a separate AC charger. In some Axperts, there is a power transformer that is part of a voltage regulator, which can look like an AC power supply.

 

 

On the heatsink that is not on the edge, they are all IGBTs or diodes. Four are for the full bridge at the higher voltage end of the DC-DC converter, one (two on some models) are for the buck converter, and four are for the 230 V inverter full bridge.

[quote[ 5 of the  9 blew up during the gunshot blast. [/quote]

We have a tentative theory that it's possible for the capacitors on the battery side of the DC-DC converter to go high impedance with age and heat, and this can cause transients on the DC bus (the 400-500 V bus), which can blow up the IGBTs. But it's far from certain. Even so, having opened up the inverter, it would seem wise to replace those capacitors.

As a point of interest, which ones blew up?

 

 

Hopefully that includes inspection of the battery-side MOSFETs. The problem is that usually the gates sort to collector and/or emitter, so you often blow up parts in the gate drivers. See below.

 

 

It may be better to leave the replacements out until you test the gate drivers when powered up. But that's pretty advanced, and we haven't figured out all the details, unfortunately. If you want to to attempt this, see this post.

 

 

You should as far as possible test all the gate driver components:

for the higher voltage full bridge of the DC-DC converter (looks like we haven't traced those yet, but from poor memory they are pretty simple)

for the buck converter (similar to the below, I believe)

and/or for the 230 V inverter

but of course only the gate drivers for the sections where the IGBTs failed shorted to gate.

Be aware that it's possible to think you have fixed the gate drivers, put it all back together, and have it fail again. That seems to be more of a hazard for the battery side MOSFETs, whose drivers are more complex, but it's still something to be aware of.

 

 

It could well be ~60% of the cost of a new inverter.

 

Hi Coloumb for your sound advice. 

How exactly does the utility power pass through system work on the Axpert ?

 1. Is it a straight through bypass of the inverter cutting the Inverter off.

 2. Or is proportional battery current used as well.

 3. If one uses the three stage switch ( Inverter, Off, Bypass ) in conjunction with the AC input and AC

     Output Isolaters, does that cut the Inverter out to ensure a straight through utility power for loads above 4000w.

Thank you in anticipation.

8 hours ago, Des said:

How exactly does the utility power pass through system work on the Axpert ?

 1. Is it a straight through bypass of the inverter cutting the Inverter off. 

Pretty much, yes. There are some relays inside to do the bypass for you. 

Quote

2. Or is proportional battery current used as well.

No, the power only flows into the battery when in bypass mode, never from battery to load and AC in.

[ Edit : only hybrid inverters can blend power from the battery and inverter with an AC source. The Axpert does however combine any solar charging with AC charging.] 

Quote

 3. If one uses the three stage switch ( Inverter, Off, Bypass ) in conjunction with the AC input and AC Output Isolaters, does that cut the Inverter out to ensure a straight through utility power for loads above 4000w.

 

I'm not aware of a three stage switch ; that sounds like something added to your installation. You can't force the inverter into bypass mode with isolators, but I believe that you can do it with monitoring software that sends the appropriate commands (e.g. output source priority). The inverter will switch to bypass mode automatically and without fuss when the load exceeds 5 kVA or 4 kW for more than a few seconds, or if the battery voltage droops too low. When battery and load are suitable for 10 minutes, it will switch back to battery mode (if priority is set that way) automatically. The inverter output phase is synchronised with AC input to make the transfer smooth. 

Edited September 13, 20178 yr by Coulomb
Added comment re hybrid inverters.

HI

what is the difference between Axpert 5kva and Axpert plus duo/tri off grid inverter.

can they be connected in the system

 

cheers Cobus

 

On 30/09/2017 at 4:37 AM, cobus said:

what is the difference between Axpert 5kva and Axpert plus duo/tri off grid inverter.

can they be connected in the system

I had posted a replied to this, but the post seems to be have been lost in the recent rollback.

Briefly, the Duo and Trio MPPT models seem to be variants of the Axpert 5 kVA model, with an additional one or MPPT Solar Charge Controllers. The Duo and Trio models seem to need firmware version 73.XX, but 73.XX can run single MPPT Axperts as well.

It should be possible to combine them in the same system, provided that they are running the same 73.XX firmware. You may have to ask for the firmware update file from your supplier. Unfortunately, the charge bug is not fixed as of 73.00, the latest I know about, and there is no 73.XX patched firmware at present.

Edited October 2, 20178 yr by Coulomb
Lost in the recent rollback. Typo.

thanks Coulomb

 

On 10/2/2017 at 1:04 AM, Coulomb said:

I had posted a replied to this, but the post seems to be have been lost in the recent rollback.

Briefly, the Duo and Trio MPPT models seem to be variants of the Axpert 5 kVA model, with an additional one or MPPT Solar Charge Controllers. The Duo and Trio models seem to need firmware version 73.XX, but 73.XX can run single MPPT Axperts as well.

It should be possible to combine them in the same system, provided that they are running the same 73.XX firmware. You may have to ask for the firmware update file from your supplier. Unfortunately, the charge bug is not fixed as of 73.00, the latest I know about, and there is no 73.XX patched firmware at present.

 

On 10/2/2017 at 10:16 AM, cobus said:

thanks Coulomb

 

A distributor af Apert Inverters claim that their new Inverter of 5 kVA actually produce a neat 5000 Watts usable power on output to the appliances at a power factor of l.00. The previous or older models only produced 4000 W due to a power factor of 0.75 to 0.8

Is this at all possible ? It sound a bit strange to me, or is the new release Axperts that good ? I presume that the new release Inverters will be a 6 kVA machine  producing a useable 5000w of power.

 

On 10/2/2017 at 10:16 AM, cobus said:

thanks Coulomb

 

We 

21 minutes ago, Des said:

A distributor af Apert Inverters claim that their new Inverter of 5 kVA actually produce a neat 5000 Watts usable power on output to the appliances at a power factor of l.00. The previous or older models only produced 4000 W due to a power factor of 0.75 to 0.8

It's perfectly possible. Has to do with the whole apparent power vs real power thing. The way I picture it in my head: If you think of two sine waves representing voltage and current, with a slight phase angle between them -- one is shifted to the right a bit -- and if you consider that power is voltage times current, then there are these small areas in your chart where the product is negative, the voltage is above the line but the current has dropped below the line, or vice versa. Essentially you're pushing some residual energy back into the generator, where it can be picked up and used by other loads.

Now consider that most inverters essentially have two stages, first it boosts the DC voltage to above 325VDC, and then it chops this DC voltage into 230VAC RMS.

Also, with DC, VA is the same as Watt. No power factor.

Now, the older Axperts had a 5kw boost stage, but only a 4kw AC-chopper stage (wisselrigter). This meant you can have 5kva/4kw. For loads with an 80% power factor, you'd be sloshing that 20% power back into the inverter and out again while the real power (the 4kw bit) is sufficiently supplied by the boost stage.

Now with the latest model, they gave it a 5kw chopper stage. So now it can do a real 5kw at pf=1. Comes at a cost though: They used FETs with a slightly higher RDS_on, so slight compromise in efficiency.

Thank you Plonkster for your detailed answer. I found it interesting and very informative.

13 hours ago, Des said:

A distributor af Apert Inverters claim that their new Inverter of 5 kVA actually produce a neat 5000 Watts usable power on output to the appliances at a power factor of l.00. The previous or older models only produced 4000 W due to a power factor of 0.75 to 0.8

Sounds like drivel to me!

The power formula for AC (single phase) is P=VI(Cos@), the (cos@) being your power factor. Power factor is a function of load, not of source - if you put a 5000W pure resistance as load (like an oil heater for example) then your power factor should be 1 and both inverters will deliver 5000watts (5000kVA x 1).

If you put a 4kW motor with a power factor of 0.8 as load, then both inverters will deliver 5000kVA or 4000W (5000kVA x 0.8 = 4000W). This is assuming that either inverter could actually start the motor which is unlikely without a very good quality soft start.

14 minutes ago, pilotfish said:

Sounds like drivel to me!

The power formula for AC (single phase) is P=VI(Cos@), the (cos@) being your power factor. Power factor is a function of load, not of source - if you put a 5000W pure resistance as load (like an oil heater for example) then your power factor should be 1 and both inverters will deliver 5000watts (5000kVA x 1).

If you put a 4kW motor with a power factor of 0.8 as load, then both inverters will deliver 5000kVA or 4000W (5000kVA x 0.8 = 4000W). This is assuming that either inverter could actually start the motor which is unlikely without a very good quality soft start.

So that begs the question, if they claim the inverter can deliver 5Kw at PF 1.0, does it have a built in power factor correction device?

14 hours ago, Des said:

 

A distributor af Apert Inverters claim that their new Inverter of 5 kVA actually produce a neat 5000 Watts usable power on output to the appliances at a power factor of l.00. The previous or older models only produced 4000 W due to a power factor of 0.75 to 0.8

I have heard the same claim. Apparently just a firmware upgrade. Since the units are rated at 5000kVA it is not a huge leap to have it capable of 5kW. They already have the 5kW Infinisolar V series which is based on the Axpert. From what I understand it is the models that have the internal SCC heatsink that have this capability.

1 minute ago, SilverNodashi said:

So that begs the question, if they claim the inverter can deliver 5Kw at PF 1.0, does it have a built in power factor correction device?

Possibly but surely that would form a massive part of the marketing campaign. The fact is that it CAN deliver 5kW at PF1 (as can any 5kVA source), but not at PF0.8

1 hour ago, pilotfish said:

Possibly but surely that would form a massive part of the marketing campaign. The fact is that it CAN deliver 5kW at PF1 (as can any 5kVA source), but not at PF0.8

exactly, the marketing might sound great but it may not perform as the sales reps made you believe

I may have gotten my explanation the wrong way round. I think they updated the boost stage to a real 5kw, rather than the other way round. The basic principle holds: The inverter has two stages and they were sized differently. It's not uncommon really. The chopper-stage is often a little less stressed. See this video for example, spooled up to roughly the right time. At 8:40 he explains the output stage.

It comes down to this again, that you cannot create/destroy energy and it must all add up. If you have a load with a poor power factor, lets say 0.8 to make the math easy (even though it isn't that bad), then a 5kva load is really only 4kw of real power, and ignoring all other losses for the moment, it means your 5kva load will only draw 4kw from the batteries. So you can pair a 4kw boost stage with a 5kva output stage, and get a 5kva inverter, for marketing purposes, BUT... at pf=1 it will only do 4kva.

They uprated the boost stage to 5kw.

On 10/4/2017 at 6:29 PM, plonkster said:

I may have gotten my explanation the wrong way round. I think they updated the boost stage to a real 5kw, rather than the other way round. ... 

They uprated the boost stage to 5kw.

Exactly! My suspicion is that they changed the DC-DC boost stage MOSFETs from 4 paralleled devices to 5. [ Edit: they may well have had to change the high frequency transformer as well; see my later post on this. ] To fit these in, they would have extended the heatsink, and to make room for that, I believe that they removed the reverse polarity protection MOSFETs, which were four paralleled devices of the same size. The latter may have been replaced with a honking great diode antiparalleled with the battery after the fuse, so reverse connection will now result in a huge splat and a blown fuse. The catalogue mentioned fuse protection against reverse polarity, from memory. 

So the inverter IGBTs were always capable of 5 kVA (not the 5000 kVA that at least two posters mentioned ), but now if the load is unity power factor, it can drag 5000 W from the DC-DC. There is no suggestion of correcting the power factor of the load. 

I hope it's not merely a firmware update as @Chris Hobson has suggested (based on others' statements I'm sure), because the DC-DC section seems to be the weakest link in the power chain already, and working it 25% harder without hardware modification seems reckless. Maybe it's technically possible to apply 5 kW firmware to 4 kW hardware, at least for a short while, but I hope that's not officially allowed. But maybe I'm wrong and the DC-DC stage is perfectly capable of 5 kW operation. That would mean over 100 A continuous distributed over 4 TO-220 packages, or over 25 A each. 

Hi, for other reasons (trying to get various inverters to accept not so perfect AC input from generators) I have messed around with the software.  What I saw was that the old (external heatsink on top) 4kW inverters will work fine with the latest software but they stay 4kW inverters.  The newer one (the ones I tested we imported in about Jan 2017) shipped with 4kW MPPT but still 4kW inverter and when I upgraded their software I got 5kW inverter power.  And the latest ones ships 5kW out of the box of course.

I cant really comment on powerfactor and such as generally when loads go that high it is heating elements (geysers, oven etc) so pretty much factor of 1.

 

4 hours ago, Coulomb said:

There is no suggestion of correcting the power factor of the load.

How would you do such a thing anyway? That's not really something you can control, the load has a distinctive power factor that you can only really change by adding other devices, for example adding capacitors to an inductive motor.

Hybrid- and grid-tied inverters usually do power factor correction, but that is a little different: They compensate for the power factor of the load by injecting their own supply in such a manner that from the supply viewpoint (ie someone from the supply company sitting in the street looking at your power factor) you get a PF over 0.9. As I recall, grid-tied regulations usually mandate a power factor around 0.9 to 1. I've actually tested this with the Multiplus, it works absolutely beautifully :-)

Hannes7212 what software you upgraded ?

So you mean new p.f.1 inverters will actually deliver p.f.0.8 till you find a software ?

 

 

A few posts back I mentioned that I thought the battery-side MOSFETs would be increased from 4P to 5P. My evidence for this is the higher losses (more switching losses from the extra devices despite the lower on-resistance losses), and the fact that the reverse polarity connection is now by the fuse.

My colleague Weber pointed out to me some time ago, and I completely forgot, that the extra power also has to go through the high frequency transformer. He found evidence that the PIP-5048 models weigh more than the PIP-4048 models. There was one document where the weight was the same, but the rated power was also given as 4 kW, so this was presumably a copy and paste error where one table was not updated from 4 kW to 5 kW figures.

In fact, he thought that the MOSFETs might be able to handle the extra current, so the MOSFETs might still be 4P.

I would be wary of any inverter that has been transformed from 4 kW to 5 kW merely by firmware change. The hardware might not be able to sustain the extra 25% of power. In the case of the high frequency transformer, I would expect the transformer to saturate with the extra power, which I think would cause instantaneous MOSFET failure (not merely overheating and an ordered shutdown due to over-temperature). But I'm happy to be proved wrong with evidence (photos of the MOSFETs and/or measurements of the high frequency transformer).

13 hours ago, cem said:

Hannes7212 what software you upgraded ?

So you mean new p.f.1 inverters will actually deliver p.f.0.8 till you find a software ?

 

 

Hi, for the inverters I mentioned in the post I was using v72.40.  The old inverters (external heatsink on top) stays at 4kW but the later models go to 5kW, like the new ones shipping now is out of the box.

 

35 minutes ago, Coulomb said:

A few posts back I mentioned that I thought the battery-side MOSFETs would be increased from 4P to 5P. My evidence for this is the higher losses (more switching losses from the extra devices despite the lower on-resistance losses), and the fact that the reverse polarity connection is now by the fuse.

My colleague Weber pointed out to me some time ago, and I completely forgot, that the extra power also has to go through the high frequency transformer. He found evidence that the PIP-5048 models weigh more than the PIP-4048 models. There was one document where the weight was the same, but the rated power was also given as 4 kW, so this was presumably a copy and paste error where one table was not updated from 4 kW to 5 kW figures.

In fact, he thought that the MOSFETs might be able to handle the extra current, so the MOSFETs might still be 4P.

I would be wary of any inverter that has been transformed from 4 kW to 5 kW merely by firmware change. The hardware might not be able to sustain the extra 25% of power. In the case of the high frequency transformer, I would expect the transformer to saturate with the extra power, which I think would cause instantaneous MOSFET failure (not merely overheating and an ordered shutdown due to over-temperature). But I'm happy to be proved wrong with evidence (photos of the MOSFETs and/or measurements of the high frequency transformer).

I agree (about being wary of software upgrade resulting in 25% more inverter...).  Those two I run at home only and they don't often see high demand but I will keep and eye on them.

So you are saying that new inverter-charger hardware with old 72.40 firmware results in 5 kW output?

Yes I have two inverters that were imported from China in Jan / Feb this year which is the new hardware (from the outside at least).  They have the updated 80A MPPTs, but still 4kW on the inverter side.  With this 72.40 software they run at 5kW (I can make 100% sure of that today).  I cannot remember what version the shipped with. 

28 minutes ago, Hannes7212 said:

They have the updated 80A MPPTs, but still 4kW on the inverter side.  With this 72.40 software they run at 5kW (I can make 100% sure of that today).  I cannot remember what version the shipped with. 

Updating to 80 A MPPT could well be different to updating to the 5 kW inverter. I'd be very surprised to see 5 kW coming from an inverter with 72.40 firmware. They can of course all do 5 kVA. Edit : I'm not saying anyone is wrong, just predicting my level of surprise. 

Edited October 8, 20178 yr by Coulomb
Not saying anyone is wrong