Project Journals > Oztules
Playing / converting the 6000watt cont 18000 watt int. (power star PSW7)
oztules:
I decided as I had so much solar power, it was time to buy an inverter for all those times when the power fails over here on the island.
I bought it from here :http://www.ebay.com.au/itm/NEW-Gen-Power-48v-240v-18000W-6000W-Pure-Sine-Inverter-Battery-Charger-Generator-/130765900315?pt=AU_Boat_Parts_Accessories&hash=item1e72414a1b
Yes it an elcheapo chinese Genpower 18000watt surge, 6000 continuous pure sine wave..... and it is too. It will easily pull the 6kw, and will easily start a 3hp air compressor with a full tank.... it does what it says.... the litmus test for me is how brutal a 9" angle grinder will start.....every bit as good as the mains next to the main power pole... this thing rocks.
It also acts as a charger for up to 70 amps (controllable), and it does this too.
What it does not tell you, is that you can also hook up a grid tie inverter to the output, and if your loads are less than your solar input, it will charge the batteries at the same time as acting as the current source for the solar grid tie..... this makes it very interesting indeed, as it will be the grid tie driving all the loads and charging the batteries most days until sunset.... inverter just supplies the 50 hz for the grid tie that does all the hard work... not the precious inverter...So.....
What this means is you can run 1-3kw solar panels without any controller (expensive at those powers)and at high voltage 300-400vdc... small wire.
The grid inverter will charge the batteries, run the house,do the MPPT function... and if you put a Ghurd controller on the batteries, divert the 240v from the output into a dump load/hot water, and the whole thing runs as a stand alone grid with storage, and if a huge load arrives, the sine wave inverter will carry the load/s.... neat......
Chris O tells me the inverters he has recently purchased don't do this, but Sunny island does, and actually controls the grid tie inverter as well by shifting the frequency slightly, and the grid tie will use this as a signal to either beef up the output, or turn it down (let the panel voltage rise) and so never o/charge the batteries ........more delicate than the dump load route......but they both achieve the same thing.
The other thing they don't tell you is that it draws over 200 watts on idle... choke choke....so 5kwh to run nothing for a 24hour period.
This is a serious omission to put up with.
True, with solar so cheap, it is still cheaper to throw up another 2kw of panels to cover this, and still be half the price of the fancy inverters ( they are 40-100w idle I think)..... but a bit steep even for me.
It does advertise that it can standby and auto start using only 25 watts, but the moment it turns on, that 200+ watts is always there to be paid for on top of your load...or another 4 or so amps@~50v.
So much for the bad. Aside from that they are very tough, run as they say, and I love em.... because they provide circuits of the power stages, both high and low side drivers etc, and would be very cheap to fix, as the output fets are only $40/100 on ebay and less.
So aside from the idle current, they are hands down winners and 1/5th or less than the name brands.... that cant grid tie and charge at the same time.
I also bought a dozen grid tie inverters off ebay for 900 dollars... like this ($75 each)
As it happens, they are galvanically isolated types..... meaning to me and my purposes, they are a cheap stainless steel box, and an even cheaper toroid transformer in the multi kilowatt size.
Here is one of the toriods undressed out of that box.
Thats over 15kg of transformer core.
You can probably see where this is going now.
Yes nearly all of that 200watts is used as magnetising current for these big transformers:
They sport primaries of about 40 in hand of 1mm wire. They are wired in series for the primary, and parallel for the secondary.... I suspect just to halve the otherwise criminal magnetizing current they would pull in parallel primaries.
So, all we have to do is wind a transformer on the toroid core and were there.
A quick fiddle with the transformer before unwinding it shows me that it is 1 turn per volt.... handy.
We want a turns ratio of about 8:1..... so 240 turns on the secondary, and 30 turns on the primary.. simple enough when you say it quickly.
I wont go into winding 240 turns of 2mm wire onto a toroid, as it is too painful to talk about, and am open to ways and means from others.
The 30 turns of the thick welding/earth cable I used for the primaries is easy enough though. ( got that wire from some old Bergy mills on Cape Barron Island south of here).
It's first flight is here.
The amp reading this time was not even on the scale
yes it is turned on.... gone were the 4 amps, now we had virtually none... (only about 100ma at this stage
Measuring the waveform showed a bit of stepping in the wave, which is mitigated by a filter that can be seen dangling beside the transformer, it is a few turns of the cable through a large ferrite core, with some spacers to stop the saturation. The caps dangling about the place were there to solve a problem that didn't exist in the end. I had strange wave forms that I could not understand..... until I realised that the earth of the scope was interfering with the earth of the inverter.... and it was still plugged into the mains as well, (not turned on, but the earth was still present)...... grrr
Also I had thought that with the tight coupling, that the original 4uf cap on the output would look like a short to the fets, but this was not the case in the finish, and those testing caps are gone now.
So what does it look like....
Here it is driving a 1.5kw load(kettle)
and the waveform (trying to capture low frequency on camera is diabolical)
Here is a close up of the final filter:
Here is the power board ( 1 side, the other side is a mirror sort of)
So with a 75 dollar transformer and a e core ferrite, we have now got a device that I have tuned up to 20 watts idle. I pushed up the idle current a bit to get the wave just right, but it can run well at lower quescient currents, but 400ma or so for a big inverter will do me fine... better I should think than most of the competition in fact. I can stand less than 1/2kwh for 24 hour idle consumption.... much better then before.
I haven't driven it beyond 3kw as yet, as I don't have any loads continuous to drive.... and I don't have enough core there to make me real keen with continuous >3kw loads .....so I don't know how far it will go, but even as a 3kw unit is it cheap as nuts, and tough and fixable.
Maybe I will put 2 toroids together ( wind as 1 so 2v/turn... I like that....120 turns:15 turns... looks much better than 240:30 from here....), and it may then emulate it's original 6000/18000 watt specs.
The computer part is isolated from the switches and their drivers.... so should be easy to fix if the board survives whatever happens.... and the importers have spare parts... unbelievable...
..................oztules
tomw:
Oz;
You obviously have way too much time on your hands! :o
Interesting stuff, nonetheless.
Tom
oztules:
Some days it's true Tomw.
Here are a few more pick of it a bit more cleaned up, but I still can't fit the top cover on it.... panel beating is next I guess.
and the logic board
And some of the circuits for those disposed to this type of stuff.
Tomw, the next story was only possible because of the help I received from the man in your sig line.... Zubbly
................oztules
tomw:
--- Quote from: oztules on February 13, 2013, 06:56:27 pm ---Tomw, the next story was only possible because of the help I received from the man in your sig line.... Zubbly
................oztules
--- End quote ---
Oz;
Can't wait to see what you are cooking up next. He was The Man and he is missed. Too bad he left so soon, I think he had lots more to share when he passed away. :'( :(
Tom
ghurd:
--- Quote from: tomw on February 13, 2013, 06:34:11 pm ---Oz;
You obviously have way too much time on your hands! :o
Interesting stuff, nonetheless.
Tom
--- End quote ---
Agreed.
Wow!
G-
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