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Project Journals => Users Projects => Topic started by: influence on June 23, 2017, 09:36:10 pm
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Hi all
Well done as always to ozules for laying the groundwork for the powerjack builds....
I finally received my custom toroidal core.....dimensions: 230mm diameter, 100mm hole, 210mm tall...
Weight has not been measured accurately but is estimated at over 50kg bare...
I will document my journey here to produce a 12kW inverter using the 15kW powerjack MOS and controller boards.
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First step was to clean, grind the edges.
Then I coated it with a potting compound epoxy...
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Then I wrapped it with Kapton tape...and then with mylar film.
I *really* don't want the core to ever be conductive....
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My calculations
Many thanks to oztules "rule" of 2800sqmm/volt as the core basis for 1V/turn
Based on my core, the core cross sectional area is 210 x 65 = 13650mm2
So we take 13650 / 2800 = 4.875V / turn !!!
Gotta love this method of using huge cores to reduce turn requirements...
So going with a ratio of 1:8 (30V : 240V)
I ended up using a ratio of 6 turns of the primary : 48 turns of the secondary.
I decided to use what I had lying around (orange 4+E cabling).
So I set the primary coil gauge to 3 lots of 25mm2 olex 90C cable and
for the secondary 1 lot of 16mm2 olex 90C cable.
Based on the above, I would require:
3 lengths of 25mm2 cable - 3.8m-4.0m each
1 length of 16mm2 cable - 28m long
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So I wind the secondary first....
Boy this was a bugger to wind...lucky I was on carpet tiles....
But seriously sore afterwards!!
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So after the secondary is wound. Lets check 1 turn on this transformer to see if we are within our specs...
Using the lightbulb dropper method. Basically as described in other topics, you take a 240v lightbulb and put it in
series with the secondary winding....you wire a switch over the bulb terminals to allow you to short the bulb after
its lit. I then wound 1 turn as a primary...to measure the 1 turn voltage...and voila we have over 5V on the one turn...
Im happy...lets wind the primary next!
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Ok primary winding time! Now if I reckon I was sore winding the secondary...guess again...
I was seriously buggered after winding 3 lots of 25mm2 together....
3 lots in parallel gives you 75mm2 effective cross section..but with slightly better heat dissipation.
See the RP7 regular sized can as a reference to size of this monster :)
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Now lets check the outputs...
Im happy with 29.5V ...this means it will work quite well at lower battery voltages...
My battery banks are 2000Ah each...so a total of 4000Ah is available to this monster.
Stay tuned. I will be assembling the noise filter choke next....
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Bigger than any I have wound thus far. As you have plenty of room, it would not be a bad thing to add a few more turns to the primary, and so get even further than the saturation point. This will help get iron losses down further before you use the inductor.
That thing is huge.
.......oztules
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Unfortunately two reasons I cannot wind more...one there is no more room and two it would raise the primary another 5V if I wind one more turn...
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Perhaps I can remove a turn or two from the secondary to reduce the ratio?
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Sorry, I meant the secondary.... not thinking straight. If we wind for say 260v not 240v, then only use 240v, we are using lower flux, so lower iron losses... so more on the primary and secondary equally ( by ratio that is )
......oztules
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Ok noted. Btw does it matter which side of the primary the choke is on?
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No...
..........oztules
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Had a seriously productive weekend...
I have used a ferrite transformer calculator and figured out the suitable turns for my choke (18 - 20 uH).
I ended up using an E70 N27 core from RS.
I did a calc for the 3.5 turns it came to about 0.5mm gap
However at 70mm2 cable I cannot fit 3.5 turns.
So I went with 0.2mm gap with 2.5 turns. It *just* fit.
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I also noticed the tracks on the boards needed some beefing up. So I added more solder and 2mm copper wire to the tracks on the FET board and just added some solder to the control board where the 50A of 230V will flow!
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The heatsink cable connection points seem a little woeful....So I added some copper bus bars to the points...
One busbar for each of the primary heatsinks and one long busbar for the +V rail heatsink.
I had some earth / neutral switchboard bars lying around....hence the odd hole or two...
Note I added a plastic support brace for the primary side heatsinks ... it makes it more rigid when fitting
thick cables....and less likely to cause the board to crack...
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I like this layout. It has seriously short cable leads (reduction in copper requirements)...
I now need to build a box, 40cm x 40cm footprint by 30cm high....thats a tiny footprint for a real
12kW inverter!!!
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Beware, if your really going to pull 50 amps for any time from the the thing in the 240v circuits, remember, you have a small CT there carrying the 50 amps in it's primary... you may need to use a current coil instead, this will keep the current off the control board too. Peaks will be ok.... but continuous will kill the CT.
My 8010 boards will run 20 kw( 86 amps@ 230v ) for start currents in big ( 5hp etc) induction motors, but they also use a current toroidal coil not a transformer. I would worry with the PJ system if it was to use 4kw or more for any real time..( the CT that is )
Will soon do an article on the finished units with gerbers, pdf etc.... just need to find the time and energy now.
...........oztules
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You know the more I look at that control board the more I dislike it...
The FET board looks ok to me.
Im catching up on the EGS002 topics...
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Its a bit unclear. Did you get the EGS002 to work reliably in a LF setup or do I have to go with the core chip and driver stages like you did on the 8010 board?
Btw will a split core current clamp like this do as a current transformer for the PJ board. Then not send the AC to the board and stick 2 x 2uF caps on the output directly?
Can I use this sort of cap instead of a 275V X2?
http://au.rs-online.com/web/p/polypropylene-film-capacitors/1964646
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Yes the egs002 works fine, but will need to have better current shutdown than the on board one. You need a small transformer to control the ac voltage as well.... do not use the generic system they show in the egs002 data sheets.
The pJ boards are ok, and the ct can be replaced with a current torroid or equivelent to replace the CT.... then yes 2-5uf can be used off board to shape the final wave ( thats what they are for ).... you mayneed to change the resistor across the CT to allow for the different voltages generated by the torroid current coil. you will find it if you trace back from the CT.
The caps you show will work, but there are better cheaper alternatives available too.....
Have not used split core current devices, but they should work fine, just re-calibrate for them.
A lot of more recent development has taken place over here
http://www.thebackshed.com/forum/forum_topics.asp?FID=4
plenty of projects using the 8010, and a few 002 boards.
the PJ is still a good board.
........oztules
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So should I aim (for now) to use the PJ Board, however, fix the CT issue and run external caps off the board.?
I will migrate to the EGS002/8010 setup later on perhaps.
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Run it natively for a bit and see how your real power usage stacks up in the real world..... then see how hot the ct gets, and everything else.
...oztules
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Ok out of interest I desoldered the CT and the capacitor....I can always put it back.
Btw the cap on the board is a 4.7uF 630V unit. I was thinking of using an external 5uF cap.... and then add some decoupling caps 0.1uF to Earth.
Ran a little test.
PJ CT: 1.65A produces 5V on the secondary
SCT013 100A:50mA split core: 1.65A produces 1.5V on the secondary.
So it appears the PJ CT voltage is 3 times the output of the SC
The burden resistor is ....
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great thread, enjoyed seeing your mods. fyi if you intend to put 50 amps through that pj control board in bypass mode... then that little pfc inductor is going to have its laquer burn up after a few minutes.
don't forget that tiny relay on there too, if that shorts closed, then the inputs become outputs - and the pj may fail to fire up. it would be quite interesting to see how it would respond to detecting its output as an input, might end up thinking it's in charge mode while inverting.. might even blow up something.
oztules.. with regards to the CT are you referring to the one on the underside of the control board?
it seems it would be wise to relocate the 240v inputs / outputs, relay, pfc inductor and ct to a seperate board with much better connections and tracks to take 50a as a 50 amp circuit breaker will allow much more than 50 amps for a minute or two before it trips.
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id be interested in what is your idle current with the new e core? as im still running on the standard toroid it came wiith. with the fans off im seeing 80w at idle.
- and when you're done and up and running, i'd like to compare how long you get 12 kw before the toroid is at 100deg c in comparison to my standard 15kw pair of toroids.
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I did not see a ct under the board on my units, but they are 4 years or more behind whatever they have now.... I am way out of the loop with the PJ boards now.
............oztules
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Hi all
I've been flat out BUT I finally managed to finish this damn inverter...and the results are spectacular....
The front...real simple, a breaker, a display and a toggle switch...
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Basically its made out of old recycled materials....
The back:
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Inside....emi filters etc....the monster toroidal core....
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Looks the goods. When ( if ) the controller gives up for any reason, there is always the newer 8010 boards on the net now, and just change some components on the fet card... and you will have a ozinverter. The control cards are very expensive now for the PJ... te 8010 are indestructable... really, three plugin chips ( at most) and your going again, but the pj is a good thing too.
Well done.
.......oztules
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Makes me want to attempt one of these now.
My inverter is getting quite old, and at this point it's just used as a backup system because it seems to have gotten unreliable.
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Hi Influence, well it looks great, I am a bit concerned that your cables are a bit small in the transformer. If you really intend to draw 12 kw through the inverter that will mean that the primary will have 500 amps through it. 3x25mm cables will get pretty warm carrying that current, especially within the confines of the transformer core. The secondary should handle the 50 amps fine but still I would suggest watching the heat. The cables are only rated at 90 degrees C.
Looks like a pretty neat job well done, I just don't want you to fry it.
I would de- rate it a bit. Generally 25mm cable is rated at around 100 amps with XLPE insulation. So I would limit your rating to around 6 kw for safety and longevity
cheers
Pete
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Looks the goods. When ( if ) the controller gives up for any reason, there is always the newer 8010 boards on the net now, and just change some components on the fet card... and you will have a ozinverter. The control cards are very expensive now for the PJ... te 8010 are indestructable... really, three plugin chips ( at most) and your going again, but the pj is a good thing too.
Well done.
.......oztules
Thanks mate. Yes I plan to upgrade to 8010 when this board dies. I also want to upgrade the fets to hy4008...
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Hi Influence, well it looks great, I am a bit concerned that your cables are a bit small in the transformer. If you really intend to draw 12 kw through the inverter that will mean that the primary will have 500 amps through it. 3x25mm cables will get pretty warm carrying that current, especially within the confines of the transformer core. The secondary should handle the 50 amps fine but still I would suggest watching the heat. The cables are only rated at 90 degrees C.
Looks like a pretty neat job well done, I just don't want you to fry it.
I would de- rate it a bit. Generally 25mm cable is rated at around 100 amps with XLPE insulation. So I would limit your rating to around 6 kw for safety and longevity
cheers
Pete
Hiya Pete, erm the primary side is 3 x35mm2 not 25mm2 and 12kW at 48V is 250A not 500A. I have a DC breaker set at 300A on the input side.
Also the secondary side is 25mm2 and then it goes to the SB through a 63A breaker via 16mm2 TPE (5m run).
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@oztules
My next step is to get an SMA 5kW grid tie hanging off the end of this inverter. Im so glad you have done the leg work to control the grid tie wrt overvoltage.
Would an IGBT work in place of a FET?
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So going with a ratio of 1:8 (30V : 240V)
I ended up using a ratio of 6 turns of the primary : 48 turns of the secondary.
I decided to use what I had lying around (orange 4+E cabling).
So I set the primary coil gauge to 3 lots of 25mm2 olex 90C cable and
for the secondary 1 lot of 16mm2 olex 90C cable.
Based on the above, I would require:
3 lengths of 25mm2 cable - 3.8m-4.0m each
1 length of 16mm2 cable - 28m long
Hi Influence, I based my post on the above information from your post.
I assumed that you were using a 24 volt battery bank because you talk of having the transformer ratio of 30 volts to 240 volts.
Seems that you changed the cable size after the post
sorry
Pete
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Your scaring me now......
30v:240v is a 48v transformer for a PJ, a 8010 would be closer to 28v:240v.
For 24v ie 14:240V.
6 turns:48 turns @48v system.......is for a very big core, or your looking for saturation fairly early on I would think.
Rule of thumb is 2800mmsq is 1 turn per volt or thereabouts. 240/48turns=5v/turn????
So you would need a huge core of 14000mmsq cross section for the torroid I would expect.... serious core indeed.
6 turn primary on say a two core inspire or aerosharp for 48v system would be pretty heavy on the magnetising current I would have thought.
The 8010 has proven to be very tough in the field. I built a number of spares fearing the worst in the hands of neophyts... none have been used for years.... very happy.
The hy4008 is a very strong performer.. don't doubt the chinese on everything.. they really know how to do it if they want to. Never had a hy4008blow in the field. Testing is another matter... try to kill them then, still I can't recall one going then either on my boards..... very large number of 4110 though in the experimental stages. Mostly because I did not realise how rigid these big tranny's are magnetically.
......oztules
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Hi Oz I misunderstood the transformer ratios and why the voltages are so much lower than the battery volts for the primary.
I am guessing that it has to do with the peak voltages of the waveform and also allowing for a bit of core saturation.
So if you stick 48 volts into a transformer designed as a 30:240 volt winding, I guess that you would end up with somewhere near 384 volts peak on the secondary waveform. The electronics must throttle that back a bit to keep the peak at 339 volts
I did not take that peak voltages required into account.
I would still think that he would not want to run the inverter at full power ( 12kw ) for long. I would suspect the transformer would get pretty warm.
Also I would like to see what the idle current comes out to be. Seems that there would have to be a lot of back emf to keep the idle currents down to something palatable.
I have only been involved in rewinding motors and transformers in my working life, I did not do any designing of windings.
Pete
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I am not a transformer person professionally.... so don't really know what I'm on about .
But ripping apart the originals, it was not hard to get some simple rules together, so that designing something that will work from the get go, seems not that difficult.
I found that around the 2800sqmm of torroid core does 1turn per volt at 50hz.... thats all you really need to know. If you go conservative from there you will get even lower idle currents.
The next thing to notice is that contrary to popular belief, loading up a tranny does not saturate it if it was not saturated at idle... so the amp turn under load is not an issue, only at idle. Once you have got clear of saturation at idle, you cannot saturate the core unless you lower the freq, or raise the voltage.
Here we can raise the voltage .. or so it seems. The battey voltage can change, so that can cause saturation if you run at full tilt perhaps, other than that, you need to be mindful that at full charge and equalization, your at 60v, so your peak inputs on the scope will appear higher, but in practice this does not seem to matter much if your using the rule of thumb windings.
So I am not an expert on transformers, but I can make them work ok. My normal run of the ,mill twin cores easily do 16kw-20kw on motor start ups, and pretty happy at 6kw cont with some cooling if we are running for 20 mins or more.
The 28:240v ratio seems to work perfectly at 230v ( where I am happy ). The lights don't dim or flicker with 2-3kw loads switched in or out at night time. which is just crazy for a 2 dollar chip. I still am amazed by the performance of this pretty innocuous chip.
I would like to think I deserved to get some recognition for the beautiful performance of these things, but really it is the little 8010 that does all the wizardry, and I'm really just an onlooker hanging on for the ride.
Some folks have taken a slightly different route than I did, and seem to have met with some ugly problems. I don't know why. They seem to well know what they were doing, but it all turned up side down for them, their reliability was shot to hell, and just getting it to work seemed out of their reach. It is only that they knew I had over a dozen working unit/s out in the field that they persevered with it I think.
So I don't know what I did right, but it is very right somehow...... just lucky I guess.
.........oztules
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Indeed my core is huge....its 230mm diameter with a 100mm core hole and is 210mm tall giving a cross sectional area of 13650mm2 which gives us (at 2800mm2) 4.875V/turn
The idle consumption came in at 85-90W with a test supply of 50V and clamp current of 1.7A-1.75A.
A little high ?
I ran some extended time tests with a 40W incandescent and checked the temperatures...
The first 3 are temps of the heatsinks. The last is the temps of the transformer at the centre....and its a larf :)
...seems acceptable to me.
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Btw fishing through some of the alipress links for the premade egs002 inverters, Im sure you guys have seen the little chart the chinese sellers have made....
Is it just me or does it not give sensible numbers?
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Yep... that be a plenty big core.... big....huge, mmonster core...
You have the luxury of plenty of room, so to get the idle current down to reasonable levels you would do well to put more turns on both the primary and secondary... maybe one more turn on the primary, and 8 more on the secondary. The further you are from saturation, the better for magnetizing currents. You will note my quick calculation up further was 14000 slightly more than you have... which may explain the slightly higher idle currents.... plus it is a lot of steel to magnetize too.
With such a huge core, less then 40 watts will be pretty difficult, but not impossible. 100w is over 2kwh/day, and thats a fair slug on a dark day. If you can get it down to 40w, it is a bit more manageable on short dark winter days.
All in all, you can power just about anything, and 12kw for 20 mins is probably easily achievable if you have the battery for it, and the heat sink/fan combo for the fets.
If your going all in with hy4008, remember 6 fets / leg will probably do well to have totem drivers designed onto your fet board. I have not had a problem with it, but others have. Four fets/leg seems very manageable without extra driving power... thats what I use. I have had no problems with 6 either.....
Re the charts, 1.4t will be heavy on the magnetizing current I would think, better to go for 1 or less to save power. Yes more turns will have higher resistance, but idle power is all the time, full power is very rare.... I vote for low idle power.
The curves for saturation will show you that there is a portion of the graph, where an extra turn makes a big difference to magnetizing current, but then the advantage of more turns drops away fairly quickly... so experiment. The 2800mmsq/volt turn seems fairly conservative, and yields fair results, but more turns is always good for the idle figures.... but too many will crimp the power handling.... always a compromise.....
......oztules
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I'd love to throw more turns on...but there isnt any room left...I think Im ok with the 90W...perhaps I can try to squeeze some by adjusting the gap on the choke ferrite ecore?
Hey btw oztules, I was looking through the backshed forum at the gti control board you made, I was wondering...where are the totem drivers on that board with the nano?
This one:
https://www.thebackshed.com/forum/uploads/oztules/2017-07-25_105729_Screenshot_at_2017-07-25_20-56-50.png
And another question the nano has a pwm frequency of 490hz, I looked at the fet's datasheet and that corresponds to a pulse with of 2ms approx...do you reckon we need to increase the pwm frequency to move further into the SOA of the fet? I have some 20N60C3 fets out an a grid tie I gutted to use as an enclosure for a battery charger....
Here is a pic of the layout of my CC CV battery charger...using tx out of a 3000VA APC ups...
Basically I rectify the 32V output of the tranies and feed it into the 1800W boost converter which I set to 57.6V and 30A.
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Interesting question..... and as usual, my ideas are my ideas.
SOA is particularly useful for the linear region in my humble opinion, but for pwm, there is more to it, and less to do with the SOA graphs, and a whole heap more with wave shape, gate source voltage to achieve saturation, and how fast we can do that and discharge the gate, and most importantly if your going for speed..... the rate of change of the gate, versus the on time and off time.
So can it handle the pulse... and what is the max pulse current we can stand.... for the 4008 is is a few hudred for the pulses, and 600 or more for the surge.... so we have that times 4.... a big number.... happy.
Now the SOA spends a lot of time looking at drain source voltage to calculate the power through the device, considering RDS on, and current through the device.... but when the fets are on, the Vds is zero, and the Rds on is also insignificant really, so provided I stay uder the Vds and Vgs, I take little notice of any other spec..... coz I'm evil basically.
What is more important I have found, is that the wave form first, the switching frequency second. With Rds on of .007R, resistance losses are pretty low...... but if your rise time is slow, your in real trouble, because in the linear region losses are basically of "A" class amplifier proportions.... so we want to get turned on seriously fast, and off the same.... Thats why I use diodes across the gate resistors.... faster turn off ( providing the impedance of the driver is low of course).... and we want the turn on/off transitions to be a low proportion of the time, as on is cool, off is cool, so we want to be in either of those states.
So we need to turn on fast, and the wave form needs to rise with almost no X slope, only Y... so it appears instant turn on on the scope. In reality, there is still a turn on time, but compared to the on time ( we are switching slow, so use a slow scope trace), the wave looks straight up, flat across the top, and straight down again. As we increase the frequency, I have always found the rising slope is taking proportionally more of our operating time, so we are spending proportionally more time in the linear region, and our heating losses in the die go up astronomically.
So if we turn on the fet and leave it on with say 12v Vgs, and 40 amps, the thing is the same as a .007R piece of wire, once we start pulsing it, provided we can keep the thing off or on only, it will cool further, the moment we start to spend any time in the liner region, we get hot......
So to keep within operating specs, and knowing I don't know what I'm doing, I ere on the side of caution, and switch slowly if I get the chance, that way I am assured of ignoring most of my foibles in the design and layout..... and things go pretty well.
If I tried to design for say 20khz, my circuits and layouts would need to be much more professional to get the same thermal result, and as I'm a hack, thats not going to eventuate.
So I build what works for me. Your welcome to change the freq. The Arduino can switch at any frequency if you read the specs, and use the internal timers........20khz and over is easily achieved apparently, I just have not done it, but plenty have. Poida on the back shed has used a Nano for the entire 8010 spwm, and had no difficulty with speed at all.
So beware, going high has it's pitfalls, and the fets run cool mostly..... but only if you pay full attention to the wave form.... or put simply and succinctly... every transition from on to off and vice versa will add heat somehow... less the better..... and most of the time there will be no pulse until the battery is charged, and needs regulating, the rest of the time it is hard on.
The totem is actually the opto, it is a 2 amp driver as well as the opto. You will need this isolation, and an isolated driver for a normal HF grid tie. A little transformer is just fine, as are the 2 dollar plug packs things on Ebay. They take 400VDC fine, or the AC from the inverter etc etc. On the board shown, the 180R gets lifted and 18vDC+ goes to it, and the pin 5 takes the - of the isolated supply. The opto needs at least 16v to run. (and <30v) Aerosharp and other galvanically isolated inverters don;t need the isolated pwr supply.
........oztules
ps electronic engineers the world over will be tearing their hair out if they read this.
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If it hasnt been said already genius is in the simplification of phenomena....less is definitely more. Unfortunately most engineers think "if less is more then imagine how much more, more is" LOL
Mate the hat is off, you would outperform most electrical engineers out there. Your art seems to have come empirically and also I notice you apply a lot of first principles knowledge. I guess Im the same way. I have had to deprogram all the engineering "learning" at uni to think empirically. I guess some habits die hard like reading datasheets and using SOA graphs... lol
I like your approach to PWM and SOA. I think its logical and pragmatic.
In terms of isolation perhaps an IGBT would be a better candidate. I got plenty of them too out of the the GTIs....
And generally they are logic level drive...
I should try it out....
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I meant to comment on the charger.
Those transformers are wound specifically to make terrible battery chargers, as they are wound with as little leakage as possible in order for them to function as inverter transformers.... But you have magically gotten over that problem by going under voltage, and using a booster with current limit and voltage limit.... in that configuration, the things against the transformers as charger, actually work in your favour, not against... I quite like it.
I am now using inverter welders that you can get off ebay for $100 and free shipping. They can have controlled current up to 200 amps apparently, I have not taken them over about 60 amps. For 24v systems, any one will do, for 48v I have had to add a single turn to the secondary on two of them, but the latest two I got do not need any tweaking, and run 50 amps out of the box... probably more, but the battery was pretty full when I tested them out. Duty cycle at 80 amps and less is 100%... darn amazing value. Simple push pull topology if you blow them up ( I have when fiddling inside them while they were on... seem easy to fix too, and use simple tl494 and sg3205 chips... dirt simple).... wait until you see the tiny simple transformers they use... just a little torroid ring less than 80mm I reckon
[attach=1]
Keep at it, plenty of fun to go yet.
.........oztules
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Interesting... what was the model/brand/style you got that worked with 48v?
I've got to build a charger for a mate...would love to try out the igbt welder version as well...
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I bought 2 of these for $198 inc shipping, they are a few bucks more now wow...
https://www.ebay.com.au/itm/ARC-250Amp-Stick-Welder-DC-Inverter-MMA-Welding-Machine-IGBT-Portable-10A-Plug/361795279692?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649
looks like this
[attach=1]
specs are suspect but here they are
[attach=2]
I just hooked it up weeks and weeks ago, and it just worked out of the box, but those specs are very odd... so hang about for a day while I test them properly... 50v open circuit???
The ones that were 60v open, needed an extra wind for the secondary, or they only ran 5 amps.... and this claims 50v.. but it worked hard???
As I only did a just to see if it worked thing, I need to do it again and be a bit more methodical before I let you blow your dough, but my very best recollections are it worked perfectly out of the box... so I will fiddle with it tomorrow or later tonight... just remembered Im off to an outer island tomorrow for the Reverse osmosis unit. Time to fire it back up, summer is coming... so tonight it is.
.........oztules
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champion!
EDIT: Omygod! 26 bucks??? same unit
https://www.ebay.com.au/itm/ARC-250Amp-Stick-Welder-DC-Inverter-MMA-Welding-Machine-IGBT-Portable-10A-Plug/382586695342
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Ok went out and pulled it out of it's case ( yes it comes in a case as well )
Don't laugh at the poor camera work... the flash won't work, so it exposed for a long time, and I am not stable apparently... but it is what it is... woeful
Ok first this is it
[attach=1]
and the camera work all goes down hill after this.
Here it is at idle at about 49v on the batts. I had to pull a few kw on a heater to get it down from the float, but it does about 10-11amps at minimum
[attach=2]
So we are on the 40 amp scale, and turning up the knob we go overload, so more than 40 amps... we get a second opinion, one on the 400amp scale, one on the forty amp scale... and it looks like this... 47amps on the 400 scale, and O/L on the 40 amp scale... so they agree about the magnitude anyway.
[attach=3]
and after a good number of minutes, we turned it back down. The air from it was still cold a good sign...
[attach=4]
Open circuit was 90v not 50v as in the blurb, which explains why this this goes hard out of the box. I didn't turn it all the way up, I saw 58amps, but it jumps around a bit at different settings, so I did not want a hundred amps turning up out of no where, as the batts are full anyway.
So does it charge... yep, does it do it for long... most likely, the two I modified, I current limited to 30 amps, and they have run over winter at a place in "town" and I use the term loosley, a pub and a few shops....and a post office may not quite make it to town status to the rest of you folks.
I do have to run these hard soon, as they will go out to an outer island... one to use, one spare... cheap chargers... and you can weld if your genny can handle it. The inverter will... but it is not portable.
So thats it, until I get a bit more time to do a proper test regime... they are ridiculous cheap for what they can do compared to a real 48v charger for a hundred bucks.
The other two I simply changed the front knobs resistance range to limit the current to something fair, as I did not know how well they would perform, but to date after about 6 months, they have been exemplary really. Did all that was asked of them. They ran for full days apparently some times, so impressive to me.
............oztules
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Thanks for the link, could only buy one at a time every 10 days.... looks like a scam, but I will give it a go, paypal seems to sort this stuff out very well, interested to see how they do the shell game this time... look like fun.
I do notice that the reviews seem very positive on this mishto unit. It is incredibly small for 250 amps wonder what turns up ;D
.........oztules
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That is magnificent....I cant believe it can just work out of the box.... ;D
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Yes I was taken aback.... but there it is. If you really want one, I would get the one from bit deals first... I don't know what will come from the 26 dollar one, but my curiosity always gets me into trouble of some sort... wonder what they will send if anything.....
............oztules
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Yeah I know....the seller looks sus...zero feedback...oh well that is what paypal is good for...
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Went to the outer island today, and took the welder with me.Used it on a 3kw capacitor drive generator.
Very odd. Barely charged the batteries..... pulled the revs up, and unit ran at 300vac, and then we got 25 amps charging????
So I suspect that the waveform from this style of alternator is a bit skinny in the sine wave or something, as the mains made the welder go hard as.....
Will try an extra turn on the secondary, and see how that changes it... very strange. Wish I had the scope out there with me.
.......oztules
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Like you say Oz the specs for that welder sound pretty flaky.
I have never seen a welder that can go up to 250 amps that plugs into a 10 amp outlet.
Those generators with capacitors in them are a probably pretty noisy, I have rewound quite a few and also changed the caps in a few as well. Unfortunately I never did put a scope on them to check out just how sinusoidal the waveform was. I would suspect plenty of noise on the output and also that the laminations were not really the right shape to give a nice sinewave. They are cheap after all, just like the welder.
Sounds like a great way to charge batteries though, as long as there is mains or a good generator about.
Nice bit of lateral thinking there.
I have used old transformer welders with a giant rectifier block and a 2kw dimmer on them to charge batteries. Bit heavy though.
cheers may the ocean be flat when you are travelling to the outer islands
Pete
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Yep, I have rewound a few of those gennies, done diodes, and replaced caps. tough a rough and ready, but work 20 years later too.
They rely on resonance between the exciter field and the capacitor, to direct flux into the rotor where it gets rectified.... so I guess plenty of places for the welder to create poor power factor in there. There is no boost stage , just the pwm stage... so the harmonic distortion, and crest problems must be pretty sad.
It is also a absolute no no to use caps in series with the grid tie inverters to stop the hunting if your using these gennies, as the caps in the input stage of the GTI effect the exciter field immensely, and the voltage will go out of control... so a fair chance a AVR style genny would drive it perfectly well.
I retested it on the mains, and saw over 56amps easily.... think about that 56 amps@54v or over 3kw It had flashes much higher than that, but the pwm chip pulled it back fairly quickly. Looking at the tranny ( or lack thereof) I would guess that 250 amps would dragit back to 18v or so... so 250*18=4500 watts..... possible perhaps for 20-30 seconds before the AC 16a breaker would go at 150% duty cycle ( for the breaker).... (curve depending.)
Anyway, the ones I did at the start of the year are driven by a 13hp honda, and have done 30 amps each for 12 hour runs during the winter.... so they do work on cap gennies, but remember I added a turn on the secondary on those ones.. as I will have to do here too.
If I get a chance to drive them with a AVR unit, before I mod them I will let you know the result. Sure work on mains though.
..........oztules
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Disappointing today. Wound another turn on the secondary, and it did not behave like the previous units... the secondary voltage remained about the same. The other units increased from 60v to near 100 volts.... so there is other circuitry causing me problems on genny power. On mains the current went up into the stratosphere... in excess of 70 amps... wherein, I quickly let it back off... there was plenty of pot to go.
The other units simply run full bore until the arc was struck, then backed off according to the pot in current terms only.... so a current controlled unit.
These ones are voltage and current regulated via some cunning algorithm.... not so easy to get what I want so easily... we have to fight against the programmer that did this.
So these ones behave totally differently to the two I originally changed. They were both different, but this is different again. There is no linear current increase with turning the pot.... it holds back at 10 amps until about half a turn then goes into the 60-70 range... and i don;t know whats past there... I sooked out.
The earlier ones were basically controllable linear.... more research needed to find out how these ones are interfering with the output according to some algorithm they felt it needed.... dammit.
So on mains sort of usable, on genny not so much at the moment..... will have to check into this more thoroughly I guess.
The other ones were through hole units, so easier to work with, these ones are primarily surface mount thingies.... so will take me much longer to familiarize with .... don't like surface mount tiny tiny things.... it is certainly much more than a waveform problem.
.....oztules
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Tried them as a welder... gee they are very good. the recommendations are right. In the 200 amps setting, it burnt straight through the 1/8 inch plate I was playing with... so as a welder. yes definitely... as a charger on a cap run genny... no ... on mains, certainly works, but not linear like the other ones.
..........oztules
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Please keep up the research OZ... i have one that is only current controlled and is brilliant when we've had a few rain days... if you can see the driver chip we may be able to help ..
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Yeah, as a welder on the ozinverter, they work very well, as a charger, they are probably too sophisticated.
I think they are waiting for the arc srike,at full voltage, at? current, then probably work out what you should be getting according to the draw...
I say that because it is the easiest stick welder I have ever used. It made me look very good.... and usually I am woeful, thats why I use a big MIG..... but there was no sign of sticking to the work, even at lower ranges.... I'm impressed, and I hate stick welders, but this one is very useable.
So if I'm hopeless with a stick welder, and suddenly I am doing excellent welds, good penetration, and the flux just falls off......... then there is something else at work here.... I cant get that good that fast..... what happened to the sparrow shi* welds I normally do?
So they are taking a lot of control out of the hands of the welder, and into some cunning algorithms....
At the moment, I have cried uncle, and just made a box with a rectifier in it, and hooked that to the genny and to the GTI... works flawlessly. Should have done that first. :(
..........oztules
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Hi Oz, are you running the GTI's backwards, I did not know that you could put 240 volts in and use them as a battery charger.
Have you given up on the old trick of just using a car alternator as a battery charger?. Maybe they aren't gutsy enough for a 48 volt system.
Seems that the KISS principle has proven itself to be the best way to go.
Pete
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Yes, the gennie puts out 240vac, rectified to 340vdc.... into the solar +- and the ac side connected to the ozinverter output (240vac)... so the GTI acts as a GTI on a local grid ( ozinverter) with DC coming from the gennie.
This allows us to transmit power up to the house from a long way away at the wool sheds.
We have two car 12v alternators up at the house for driving the battery bank directly. Both are just 12v alts with home brew regulators. They output about 25 amps @ 55v or so..... with both running..... then 50 amps etc. You can squeeze 30 amps out of them if you push the gennie motors very hard.... but they are only 5hp motors ( 2 off)
Add in the wool shed GTI, and we get 75 amps.
The wool shed is good as it is so far away, you can start it up at night in winter, run the Air Conditioner/heater, and let it run out of fuel at about midnight.... then the GTI drops off as if the sun went down..... and very quiet.
.......oztules
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Hi,
I noticed that a few folk are following this topic.
I am Still editing the 2nd edition of the OzInverter book.
For those that are thinking about the toroid build, here is a couple of pages with the formulas and calculations. And some examples.
I trust this helps.
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Nice few pages, but that oztules bloke got it a bit wrong,..... he was obviously saying 240vac, and thinking 230v or thereabouts which he uses.......or just not thinking at all......... which I know is what he normally does.
The real 240x1.414 comes out to about 340v peak... what was he thinking >:(
So you need to change the 320 to 340..... oops.
..........oztules
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Thanks Oztules, for the observation.
Here is the updated version of the TOROID explanation.
[attach=1]
I will check with you before going to print so that any other modifications/idiosyncrasy's can be amended.
Thanks again.
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Hey I got some interesting news....a neighbour bought a welder from ALDI...a "Workzone 140A" unit...so i said to him let me measure the Uoc...
Came in at 63Vdc. The box said 72Vdc....
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Btw interesting observations about the PJ inverter I built...
Transformer stays fairly cool BUT....why does one of the heatsinks get hot (one side that goes to the transformer primary) and the other 2 stay cold ( the + side [long one] and the other side that goes to the transformer)?
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Also I had a play with the new 2018 Powejack 15kW unit....they use a large toroidal and TWO mos boards....and the modular control board.... pics if youre interested.
I ran a test on a mate's place....turned everything on...it held up....
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One will be switching fairly slowly, so only a hundred or so transitions per second.
This means the transition time versus time on is big... ie the transition time is small compared to the saturated states... so most of the time they are on or off, and not very often going in between states ( where the switching losses are highest, and so least efficient... more heat....) this is then the 50 or 60 hz switches.
The other side of the switching is the spwm signals, and they transition 20 thousand times per second or more.
As you can imagine, they spend a lot more time coming and going between on and off, than the slower 50hz switching fets.. These fets need to turn on and off 20 thousand times while the slower switches only do a hundred or so.
From memory, the high side switches are provided for by a galvanically isolated pwn supply, so high side losses are kept to a minimum, ie the high side should be as efficient as the low side with it's switching. They use pretty hefty isolated drivers for this that should have very good wave forms.
In the ozinverter, we use current pumps, and this lowers the efficiency slightly for the high sides, but it is not that significant, as the losses caused by the opto in the pj's probably is equivalent anyway. The high side spwm on that PJ has twice the coolig as the low side spwm, and that will help it seem better.
I don't know how they do it now, but either explanation will cover it I expect.
The inverter welder will power a 24v battery bank as it stands... probably only less than 6-10a on 48v pack.
6-7kw is nothing to be sneezed at, the PJ can deliver a pretty handsome house inverter from the looks of it. We are getting pretty blase now with these big transformer inverters now.... no one blinks at all if you get into the 6-10kw range for short periods now... who knew....
Interested in your findings on the newer style.
.......oztules
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Hey OZ, we should start a new thread on these inverter welders...
I dont have any photos but i added an extra turn to the " transformer " and found a potentiometer ( 3 actually ) that read " max " and wound it up.. delivers close to 4 kw now consistently and still strong. Gets hotter than originally, but i did run it for nearly 20 mins and didnt seam to mind... has a .4amp 24v fan that runs constantly so that greatly helps..
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Probably could.
From the looks of it, it is difficult to know how much smarts each brand has. The less the better for us.
Those new ones I got hold of are brilliant as welders, but a bit unreliable as chargers, as they think too much about whats going on... trying to improve the welding experience.... which does not help charging....
The slightly older chunkier ones I had, worked perfectly linearly once the extra turn was applied.... so horses for courses I guess.
...........oztules
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So... 8 solid hours charging at 3.9kw and never missed a beat... solid as... batteries needed a good balance charge as we have had on/off rain..
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https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com.au%2Fulk%2Fitm%2F131818334056
This the one i have, VERY well built.
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Its on sale now so I reckon you could do worse for $92 delivered...
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Interested in your findings on the newer style.
.......oztules
Thanks oz. The explanation works for me and is now driving me to move to the EG design.
I have had some issues develop with the new PJ. After about 3 days the power started to blip (brown out) every 18-20 mins.
Turns out they run a beefy 12V fan off the pj board and the load is pulling the 12V and 5V rails to almost 0 instantaneously. This results in the "talking inverter"
to say "70% load remind"....
So to fix this, I cut out the 12V fan and fitted a 230V fan with a 45C thermostat on the transformer.
The Other two fans are 48V and run off a JUC-31F 45C thermostat fitted to one of the slow switch heatsinks on the mos board.
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Here is a video I uploaded of the fault.
12V fan dips board voltage causing brownout
Another issue. MOS Board flicker
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Not keen on the flicker at all...... looks like a fundamental problem in there somewhere on the 48v supply rails.... no idea how they have done it, as I don't know that style at all.
...............oztules
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After bypassing the 12V fan the new PJ seems stable. The flickers are gone.
Still....too right oztules. I want to move to EG8010 boards.....