8 KW LF Pure Sine Wave Inverter 24 to 240 Shut down Issue

[Lachlan]

I build my own house and went off grid - solar only. I am not so clever on the electrical front but decided to be brave and have a go. Bought my own panels 16 * 250 w @ 24 v - batteries lead acid with about 600 ah rating and the power jack. Actually had three inverter's now. One to  build the house (not pure sine wave), one that blew up within 5 minutes (was a dud) and the current 8 KW model which has been a champ......so far

I have been running the inverter for about 9 months (started in middle of summer) - sweet as - runs the house well - vacuum cleaners, kettles, washing machines.  Everything works well and power during the winter was not a problem. Had to ration power on the really cloudy days (i.e. no electric kettle) but no hassles. So now the summer is here and lots of sun but.........

Last week for the first time my inverter tripped off. I had just topped up the batteries (lead acid 600 AH @ 24V) - nothing unusual. So it tripped and the warning it gave was over voltage - that is about 1 minutes of beeps followed by shut down and continuous beep but green light on.
Checked voltage and was sitting at 27.5 as it had been. However decided to turn the solar controllers down to 27 to be safe. Turned back on - ran fine for about an hour then same thing again. By now it is getting to later in the day. Called a mate and we had a discussion on it all and decided to drop it to 26.9 and try again. Worked fine and ran all through the night. Yay!!

About midday the next day same thing. Turned it off and gave it a "rest" and put it back on again in the afternoon. Again it worked all through the night and into the next day till about mid day. Shut down time again. This has been the cycle for a couple of days now.

One thing I have noticed. When we run a load the big fan is coming on as it always has, but all the time I am in the shed recently I dont hear the small fan cutting in like I used to. Would have though it would have shut down with over heating warning but no. used to hear it coming on and of all the time.

Has anyone got any ideas on what is going on? And what I might try and do to remedy the situation?

Love being of grid but you feel so vulnerable when the inverter goes.

Lachlan

[David HK]

Lachlan,

You announce yourself as a newbie but could you please tell us all which country you live in? This would be most helpful so that readers could put their own situations in perspective to yours. It all helps people to understand your achievement.

David in Hong Kong

[oztules]

you have more sun now than in winter, and your batteries are getting to float much easier. Is is at this time the spike problems occur with pwm voltage control of your solar system.
Discussed many times before on here...... so, a 1m resistor across the R14 10m resistor will probably stop it happening, I use a 5v6 zenner across the 10m resistor cathode to the main chip.... this will stop it too.

...............oztules

[Lachlan]

Hi and many thanks for the reply David and oztules

David HK - I am in Australia. West and about as far south as you can go before getting wet feet. Out of town and no power no water (or at least not without incredible cost). A mate who has been doing wind and solar for about 6 years (same situation) said "we can do this" and so the journey started for me. Mate has been doing own repairs on wind turbines and built a few panels from scratch is pretty handy with the solder iron but the inverter is a little beyond us both although we understand the basics (him more than me). There is a few others like us about the place here - that is off grid without going through "the system" - no government rebates etc. We share between us what we can. Important to note that everything from the inverter onwards is licensed work - that is everything at 240 V is by licensed electrician. Solar panels are fairly straight forward as is the batteries. The inverter is our weak spot and nothing local to help us out. I should mention my father was a TV/Microwave technician and still pulls computers/electronic equipment/washing machines apart (generally from throw out your rubbish days in the city) and reassembles them with various "brains" as he calls them. Also have access to mates who can fix electrical music equipment/sound systems etc. I guess what I am saying is the skills are about but not the knowledge.

oztules - I have been reading your notes for about a year now and saw the recent one on the 6KW inverter and it had me thinking it may be the same issue. When I fist found this site I thought "we are not alone". I have read what you have said but is there any particular posts from before with more detail or a diagram/picture? I am the one who will collect the information - not do the work - so if you think I am a clutz - your right! but incredibly grateful - and learning all the way.

Q - why has the pwm (that is post wip modulation?) of the solar control changed from last summer? It did not have this issue before in mid summer so a bit confused why this has changed?

Again many thanks

[Lachlan]

you have more sun now than in winter, and your batteries are getting to float much easier. Is is at this time the spike problems occur with pwm voltage control of your solar system.
Discussed many times before on here...... so, a 1m resistor across the R14 10m resistor will probably stop it happening, I use a 5v6 zenner across the 10m resistor cathode to the main chip.... this will stop it too.

...............oztules

 See my message reply on this - cheers lachlan

[ClockmanFrance]

Hi Lachlan,

I have been constructing Oz's 6Kw Inverter.
Total cost for all the bits I needed to buy was about £500 GBP.



Oztules notes and jottings are excellent and in my opinion sufficient to produce a good machine. My 'OzInverter' LIVES, and it 'cocks a snoot' at my expensive SMA Sunny Island 6, which never did do what what it says it is supposed to.

My 'OzInverter' is in at present, as I fit all my Meters and finish.



The Transformer and PCB's are the heart, and Oztules way of manufacture is actually straight forward. Commercially winding them at that size is probably just not cost effective.

I will, sometime over the coming winter put my 'OzInverter' construction/manufacture story, into a Booklet form with lots of colour Photographs etc, which may help others.

This is my Not for profit 'Make your own cost effective 2kW PV Solar Tracker' booklet. And I will do something similar with the my 'OzInverter'.
http://www.echorenovate.com/new-book---make-a-solar-tracker.php
(Sorry Mods if this link is inappropriate please remove if you think necessary, we are Not for Profit.)
 
My French sheep checking my installation of No3 Tracker?

[oztules]

try this http://www.anotherpower.com/board/index.php/topic,902.msg9296.html#msg9296

did you add panels this year?..... using less power this  year... or we have a  different problem. Try the zenner or the 1m resistor and see where we go from there.

The fan programming is a total mystery to me... and them  I think... it changes characteristics all the to me... I don't use theirs.

It is possible that your fan is sending no tacho information too, and if it is running weird, then this is a possibility too.


................oztules

[Lachlan]

oztules - many thanks for your consideration and the link to info -  Will try 5v6 zenner as you suggest - help at hand this end - all knew exactly what you referred to

On the issue of changes in the last 10 months - none - no new panels - usage has been constant. This is what is throwing me a bit.
The small fan (I call it the small one as apposed to the big one which is working as before) is the thing I think has changed - as well as the tripping each day about midday but never under a good load. Always trips while nothing much is happening. The small fan does not come on as it did. In fact over the last couple days I have not heard it on once.   

So I have to ask what is "no tacho information" you referred to about the fan not sending means.

As we put in the zenner I was planning to replace/look at the small fan anyway as part of ticking of boxes.

Any thing else to consider and check while the lid is off as part of "while your at it" type stuff?

Lachlan


ClockmanFrance - when I see what your doing I believe more and more it can be done and schools need to teach more about all this stuff. Without taking the fun out of it it should be mainstream info

[Lachlan]

So - here is what happened so far............

Last couple of days were a bit cloudy and we have not tripped out once but had solar controllers set at 26v to reduce the tripping.

Got a spare inverter (same type etc. = PJ) and swapped over. Turned up the Solar Controllers to 27v and waiting for any issues - none. Over to working on the old one.

As soon as we got inside we noticed the fan in between the coils (what I call the small fan) was stuffed - and wobbly. However having a spare (with broken blade) about we swapped over good blade to good motor and tested. Knew fan worked (albeit a bit old) so put it in and set about a test. As soon as we turned the old inverter on (without any load at all = 0) the first thing that happened was the small fan started. It ran for about a minute then stopped. Have old inverter running with spare with controllers set at 27v and no issues so far.

Seems we may have found the problem on mine.

Any ideas anyone on what type of fan to get to replace the old one? Like would a bearing fan be better? Would really appreciate some help on getting a decent fan to replace these ones with.

My friend who had a similar issue found his fan was OK and strong. So we have placed in a 1m resister. So far so good. Always good after these things that nothing blows up!!! Now we wait and see........

[oztules]

 I use beecroft fans off ebay... they are easy to convert to tacho units to use as the PJ primary fan, or just to use as normal with your own fan circuits.

The PJ needs to see at least one fan with tacho.

Really does not matter what you buy, they can all be made to give a tacho signal... but try to get ball bearing style if possible.


..........oztules

[Lachlan]

Update....
As I said before we bought a new inverter with the thought of having a spare between my mate and me. The old inverter apparently had a problem with the fan (the 120mm x 25mm that sits between the two coils) so we ordered a replacement with a view that this could be a spare.
 
The new inverter I bought has been running fine although tripped out one sunny day when nothing was happening (but only the once). My mate who has wind and solar placed the 1m resistor at R14 in his and it has been running well and no tripping out from over voltage. Thanks for the assist with that issue.

Finally got the fan we needed after initially being sent the wrong size and having to wait yet another month. In the meantime got fed up waiting and also bought a bearing fan (Beecroft). As it turns out we ended up with two fans (nothing like a spare I thought). Today we finally both got together for fixing up what we hoped would be our spare inverter. Replaced the fan (with the bearing fan) and also put in a 1m resistor at R14 (just to be sure) and hooked it up for the big test........

As soon as we started it we noted that the fans did not trip in but understandably so as there was no load and it would have been cold from not working. So I set off and started up a kettle to give it some stick. And we watched for about 30 seconds..............still no fans kicking in and when the smoke started coming out of the power outlet end we decided it was perhaps the best time to shut down. We then (quite quickly) unhooked everything..........back to the workbench and had a look. Signs of smoke near the the fan we just replaced. We took this out and tested it and sure enough this was cause of the smoke. So we got the other fan (tested it to make sure it was working (all good). Put this fan in and hooked it all up again but this time with the top off so we could see what was going on. Same process, still no fan kicking in but this time soon after we turned it on we both saw the arc flash near the mosfets and again decided this was the best time to shut down. We looked but nothing obvious at this stage. Tested the fan again and it was still working. Again we unhooked it all but this time replacing it with the inverter that was working but now with a 1m resistor to hopefully stop that over voltage issue. All good and working as before.

So now a fair bit of head scratching on the old one and wondering if we have to strip it all down but we are now out of our depth. Like we can take it apart - perform checks - identify issues - replace parts but we would need guidance on what to do. In our discussions we agreed that it was a pity that we had no one we could take it to in Western Australia (that we are aware of?) but if we can get a guide we can have a go. Even if we could send it to some one in Australia it "might" be worth it. Alternatively in our discussions we agreed it might be just easier to buy another for our spare but it seems a cop out and a waste.........and we don't get to learn anything (which is always good ....even for a couple of over 50s die hards who believe that this is the way to go)

All the above issues might be completely unrelated - like a spider could have go in while we were waiting for a replacement fan or what happened might be the underlying cause of it tripping out in the first place - no idea. 

So.....has anyone got any thoughts/views/ideas on how we might proceed?

Tested but still loving it

Lachlan and his mate
 

[oztules]

I have only seen one inverter with the "mid fan" in the transformer area... and that was a 48v fan... wondering if yours was 12v or 48v... that would explain the smoke part.

The failure.... no idea, unless it had something to do with the 12v fan coming from a 48v point on the board, and interferring with the power suply part....

Things you can do. If you pull out the power board. ...........Replace the fets and the resistors that will be cooked. This will give you a new power board, there is really nothing else on it.. just fets and resistors few caps too.... but no tricky stuff.... hint cut the legs out before unsoldering... so you only lift one wire out at a time, this will help NOT destroy the solder pads.

The control card.. this can be pretty disappointing if the problem goes past the totem drivers and the opto isolators.... may be best to just buy a control card.. they are fairly cheap...... else replace the totem driver transistors, and the opto isolators.. and cross your fingers.. big time...

No harm in trying. Fets from aliexpress are of less than perfect specifications, but for the momney ( usually can get 50c/piece) generally around the .006-.009ohm... which is pretty good, and makes for cheap experimenting. Dinky di ones may be a few bucks each, and be very expensive to blow 24 of them up at once.

I wonder how I know this...

...........oztules

[Lachlan]

Oz Thanks for the reply. Really appreciated
Ours are both 24V systems (both have the fan between the coils and one at the input end) and the fans are the same V. Pretty sure we got the info off the the old fan right when we had a look at it the first time and magivered a 24V fan which worked but was not a reliable fix. 
The rest of what you said, like always, we will have a chat about over a few days and try to absorb the information you have provided and see if we get our heads around it all. Your right ...you know a lot of stuff.
You really have me wondering about the fan V. The input is 24V from the batteries and the fan is connected to the input.......... is it possible that the mid fan is only 12V ....how does that work?

Lac

I fully realise how much I don't know is amazing

[Lachlan]

Yep you were right - just checked the bearing fan I bought. They had sent me a 12V and not 24V that I ordered. Lesson in checking what was ordered. This would explain the smoke?

Now onto the rest of it..........

Lac

[Lachlan]

So we tried (you have to try)

Stripped it all down. Found the arc point which was at the point where the transformer lead connects to the heat sink (the black one). Problem seemed to be a combination of loose screw and heat shrink over the terminal - poor contact. Rather black. So we made good the connection..

Decided while we at it we would go all the way and make sure nothing happened around the fets. All good and no signed of damage. Testing no short circuits and resistance was the same on three sides. 

Just started it up and it works but now giving up to 270 V output. So now way way over.

Have we perhaps cooked something else? Is there a point of regulating output voltage? Or is there a point at which we can test for damage to something else?

Must say we are learning a lot (but never enough)

Lachlan