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

[oztules]

There is a resistor string that the computer uses to sense the ac voltage and direct traffic from there... cant remember which ones ( it is mentioned in one of my previous answers somewhere). You will see the resistors coming away from the 240v area... strings of them, one string is for syncing to the mains for charging/ups, and one for voltage reference ... I think that is how it goes.

If I get time I will try to get the numbers for you.

They are very high R, so very high impedance, and easy to change the ac by even dampness or dust..... bit scary really, but seems to work in practice, but they are in the order of megohms..... if there are any problems with any of the resistors in the staircase, then the voltage will move. A shunt across any one of these will drop the voltage, as it sees a higher reference sooner.


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

[Lachlan]

Cheers for the reply OZ - always something new to consider/learn and always gives me hope!

Will look as suggested - I have my 80 year old father with me at the moment (ex TV and Microwave Tech from the old days) so this is keeping us in constant theory (Ha!)

Numbers would be good if you have the time

We do not use charger/UPS function - only inverting from 24 to 240 - does that make any difference with potential issues? Eliminate any?

Note from basic me only (don't laugh...too much)
On the back of the control board there was a couple of bits of of masking tape taped across the back - I thought "what is this doing here?" and it was .......ummmm "tatty" But decided if that is what they want then so be it.......... it was grubby. Could that be enough to alter V ? Sounds ridiculous I know but...... My father tells me it is to protect the components from people wearing silk shirts! I will take a day (maybe two) to get to the bottom of that! Is this really what is needed to cover back on control board? I am really sorry to sound so thick but.............I am

Lachlan

PS I am becoming at ease with the quantity and quality of the massive amount of stuff I have no idea about.

[Lachlan]

Your right! They are very susceptible to dust. Removed the control board. Removed the tatty bit of masking tape from the back of the control board. Gave the whole board a really good clean - all back in and BINGO 239 to 240 V output in stage 1 testing (via jumper leads). Stage 2 testing to follow shortly (proper hook up and ask it to make 3000 W).

Fingers crossed

Lachlan

PS why was the tape across the back??

[oztules]

"PS why was the tape across the back??"....................probably to stop just that.... except it did not work as they expected me thinks.....


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

[ClockmanFrance]

Just had my latest set of 15kW boards apart........

[ClockmanFrance]

A little excess solder flux splatter.......

[oztules]

One of their better boards.......

..........oztules

[Lachlan]

The picture of the tape on the back of the control board looked just like mine except mine was a bit more worn and torn and looked like dust had got in underneath. Should I be re-taping it? (with new stuff!).

I tested the unit fully today and the results were as follows: -
- Start up OK and making 237 to 238 V
- Got the output over 3000 W and no sounds of "snap crackle or pop" or smells that worry you or flashes that do the same and it held steady (we are nearly there me thinks)

BUT (ha ha not so fast) - No fan kicking in. So I boiled up a bit more water...and still no fan. I left the unit on for about an hour or so doing what it normally does (which is very little - about 300 W runs the house most of the time). The day was very hot here getting to about  36c in the shed. The case was starting to feel a it hot so I got worried (I am a coward and did not want a melt down) and shut it down and had a look. The heat sink was hot as was the coil - hot to touch and you would not want to leave hand on for too long. I am thinking something is not switching on the fan.

My backup inverter fan will kick in as soon as I load it up over 2000 W.

I know the fans work because I tested them. I am wondering if I have damaged the heat sensor when I put the 12 V fan in error before (the one I made smoke as mine is a 24 V unit - whoops and lesson learned there).

Is there some way I can test to see if the heat sensor is working? or the control board end? I assume it is the one on the top of the coil - wired to the control board? Other thoughts?

So close and yet......

Lachlan

PS when you learn you learn there is more

[dochubert]

Hi,
My 2 cents worth;
On my inverters, the sensor on top of the coil has some bare metal pin sticking out where they attached the wires.  A screwdriver shorting those pins will run the fan.  A set of wires and a toggle switch instead of the screwdriver gives you a switch to turn on the fan whenever you want, irregardless of temperature.  Nice to have.
None of this tests the sensor, though.
I use a non contact laser thermometer to read coil temp or whatever, but I haven't tested to see what temp turns on the fan.  You need to know that value to be able to tell if the sensor is working or not.  With that value in mind, run the unit til the coil temp reaches the value and go from there
Hope this is of some use to you.

dochubert

[dochubert]

Another thought just came to mind...  (and boy did it hurt)

The sensor on the coil nearest the power switch end of the unit (if yours has more than one coil) turns on the main fan.  Also, the sensor on the side of the mainboard heatsink (it plugs in near the main fan power connector) also turns on the same main fan.  When testing, you will want to be sure which sensor is turning on the fan.  If the unit will run with that heatsink sensor unplugged, then you would be sure only your coil sensor signal was controlling the fan.  Be sure to monitor heatsink temp while running its sensor unplugged, and not something I would do for too long a time or run unattended.

Maybe you could just run it for awhile to warm it up, then use a heat gun to cook it up a little more to test the sensor.  It would tell you it works, but not if it was turning on at the correct temp,  Still need that value...  maybe someone else here knows what it is.

[Lachlan]

Thanks for that - good thoughts. Had considered the heat gun but thought there had to be another way. I will try just getting the fans to run as you suggested and then move down the line to see what is and is not working.

I always thought that there was some sort of other thing (in addition to temperature sensor) that tripped the fans on. Because when I use  more than 2000 w the fans would always kick in immediately. I assumed that at a certain output it came on and the brains for it is near the main chip.

However my fans on this unit always seemed to have a mind of their own. I am sure that the fan in the middle of the coils would come on by itself (which when I look at it seems impossible!).

Your assistance and thoughts are greatly appreciated.

Lachlan

[dochubert]

No problem.  Hope my ramblings helped
On my 48v unit there are three coils and three fans.  The additional fans are powered directly off of the dc input (no fuse or breaker) and have no connection to the control board at all.  If you trace out the wires back from your 2nd fan you should see that they connect to a sensor on the 2nd coil.  Same deal; shorting those sensor pins should turn it on, and you can put a switch on that fan too, if you want.
As far as I know, the fans are only temperature controlled.
My 8kw 24v unit only has one coil and one fan.  Not sure if thats good or bad, but it never had any trouble handling loads.  The fan did seem to run alot on that one.  I suppose the single coil gets hotter sooner, so the fan runs more.
Hope you solve your problems

dochubert

[johna]

I just had a bit of trouble with my middle fan, it would not go off,so i pulled the sensor off to have a look at it, it is held on by some black goo.easy to take off ,checked it out it was shorted all the time. so i put it in the freezer to see if it would close it, that worked.put it back in and its ok for now so i ordered some more because its liable to do it again.The middle fan sensor is a 45 c degree one(KSD-01F 45C NO Temperature Control Switch Thermostat),as this one comes on first i would say the one for the big fan is probably a higher  degree sensor, they sell them in 50c and 70c as the nearest so it could be one of those.
john

[oztules]

The big fan is dynamically controlled via the temp sense and the computer.
I have never nailed down how and why it comes on, but it has tacho incorporated too.
The center fan is a dumb fan via therm switch as you discovered, but it usually also has a sensor that the computer can see, and will shut down the unit if too hot.

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

[dochubert]

The more I learn about the fan controls and their apparent inconsistent (read; unreliable) performance, the more I am inclined to follow Oztules lead and put in place independent fan control.   I remember reading that Oz built his own, but I'll probably buy a temp control card off ebay (dirt cheap) and just parallel its switch with the existing inverter's sensor.  That way, whichever control wants the fan on first wins, and my inverter stays cool either way.  Maybe even two cards; one for heatsink temp and one for coil temp.  Two temp control cards with sensors for less than $10US total is too cheap NOT to use.
I have noted in the past that some days the inverter seems to run hotter than other days, but without actual temp readings, I just thought it was my imagination.  Not so sure now...  The cards I'm looking at will also give a constant temp reading, which is a nice plus.
I guess that just leaves us with the question of where to put the setpoints.  On at 40-45 maybe and off at maybe 35?  Oztules, what setpoints did you use and did you sense at the heatsink or on a coil, or both?

dochubert