Author Topic: Building a 6kw pure sine wave inverter using power jack boards part1 transformer  (Read 24938 times)

0 Members and 1 Guest are viewing this topic.

Offline andymack

  • Newbie
  • *
  • Posts: 23
  • Karma: +0/-0
AeroSharp 2k5

I have blisters, sore shoulders, tired but the core is stripped of all its windings - just have to remove the final bit of tape.

I believe the  core is exactly the same.  193mm , 86.23 hole, 68mm high  - ancient bathroom scale weight ~ 10kg

You right john, the bobbin with the right size is best.

Now have to dismantle the other AeroSharp and do it again   ::)

Andrew

Offline oztules

  • Moderator
  • Hero Member
  • *****
  • Posts: 1177
  • Karma: +105/-8
  • Village idiot
Welcome to the club..... look at the final picture of my transformer for encouragement... it is worth it in the end.

The island seems to be scarce of heavy wire... so it looks like some very very hard to bend 40mmsq will have to do this time.... it is gonna be hell to wind.. stiff as a board.

.............oztules
Flinders Island...... Australia

Offline tomw

  • Not as bad as you might think
  • Senior Moderator
  • Hero Member
  • *******
  • Posts: 739
  • Karma: +35/-0
  • hoplophobic people will fear my lifestyle
    • Zubbly's photos!
You guys are animals.  ;D Nice to watch, I must admit.

Do NOT mistake me for any kind of "expert".

( ?° ?? ?°)


24 Trina 310 watt modules, SMA SunnyBoy 7.7 KW Grid Tie inverter.

I thought that they were angels, but much to my surprise, We climbed aboard their starship and headed for the skies

Offline andymack

  • Newbie
  • *
  • Posts: 23
  • Karma: +0/-0
It certainly will be worth it - Keen as mustard  :)

Miserable day in Brisbane today so a perfect day to pull my 2nd AeroSharp apart. 

For all the bagging the AeroSharps have received I have to say I'm really pleased at the quality of everything inside the box - all good quality components, neat design, good assembly.  I'm going to have lots of spare line filters, big volt caps, huuuuge heatsink and more  :)

John, if I understand things right, by having a few more turns on the new transformer (as in 123 vs 114 turn) , will decrease the flux density, but will have no negative effect on the transformer action itself, just increased copper losses,reduced winding room ?

During my hours of unwinding I had a thought that i should have a tap on the primary for 24volt system, say at turn 7?    (This transformer in destined for a new 48v system but my present system is 24v)  may be useful for experimenting before I get my 48v system.

Andrew


Offline oztules

  • Moderator
  • Hero Member
  • *****
  • Posts: 1177
  • Karma: +105/-8
  • Village idiot
"John, if I understand things right, by having a few more turns on the new transformer (as in 123 vs 114 turn) , will decrease the flux density, but will have no negative effect on the transformer action itself, just increased copper losses,reduced winding room ?"

Close enough explanation. less steel, more turns more copper loss.

If we think the idle current needs to be lessened further, then more turns on the primary and secondary .
This means for the same inductance, the core will be less magnetized.. so less iron loss... but more copper loss.... but at idle, the copper loss will be virtually nil, and if we get the iron loss down, then our standby losses will be less.... a case of deciding where to stop really.

So, if you expect that the thing will run at low wattage most of the time, then more turns is the answer.. but if you think it will be running high loads for longer time periods, you may decide copper loss needs the attention.... like everything else.. it is all balancing plates in the air.

Addition.... if you want to tap, perhaps wire in the primary in two half winds , rather than center tap. That way in parallel, you have 24v full power, and series for 48v full power.



...............oztules
Flinders Island...... Australia

Offline oztules

  • Moderator
  • Hero Member
  • *****
  • Posts: 1177
  • Karma: +105/-8
  • Village idiot
Well had to use 30mmsq wire... hard as hell... might just as well have been solid core... it was very nicely work hardened.

After making lots of gutteral noises, we ended up with this.... thats after using the car and a 6 ton guillotine to stretch it straight....

4006-0

It will easy do the 6kw, as in open air 30mmsq it is good for 180amps.... and thats well over the 6kw we wanted.
Or at 6000w, we will have .66% loss in the copper primary, and even less in the secondary ( 40 watts lost@6000w in the primary and about 17w in the secondary ) .. more than I would like, but less than 60 watts is controllable and about 1% loss or less all up ... plus 25 watts lost in iron loss... 85w total from the 6000w so 1.4% losses total from the looks of it) The air spilled from the mosfets fan at that level will keep it easily cool enough. I suspect.

................oztules
Flinders Island...... Australia

Offline andymack

  • Newbie
  • *
  • Posts: 23
  • Karma: +0/-0
nice ...  :)   look forward to reports on the testing.

Finally stripped both cores,  I think I was just getting the knack too ..  I'll join them tomorrow, then i have to leave it for a little while, meantime sort out the bearing wire straightener. 

Andrew

Offline MadScientist267

  • Impossible Condition Curator
  • Hero Member
  • *****
  • Posts: 1514
  • Karma: +44/-4
  • Rules? What rules?
You guys are animals.  ;D Nice to watch, I must admit.

I'm with you all the way on this one Tom LOL

I decided with little 1.5" cores and like #16 solid that I really didn't care much for [un]winding toroids... This monster blows my mind... I envision plenty of cussing, lots of sweat, and the urge to throw things. ;D

Keep up the good work, Tom's right, this is fun to watch ;)

Steve
Wanted: Schrödinger's cat, dead and alive.

Offline oztules

  • Moderator
  • Hero Member
  • *****
  • Posts: 1177
  • Karma: +105/-8
  • Village idiot
A quick mock up shows that the entire inverter will run at 30 watts idle current with no sneaky mitigation like the big boys do.. ie switching in and out small transformer for small loads, and big lossy ones for the bigger loads... so our iron loss is less than probably 20 watts no matter the load.... the other 10 watts is in the drivers and logic etc.

Pretty good for 60lbs of transformer I reckon.

Torroids really are the best, but very expensive steel, and a real hand full to wind. They can do twice the power of a good EI of the same size, and are half the weight for the same power.... thats means it would need a 120lb transformer of the EI type to catch up to this one.... something to think about when your winding... and imagine the idle current on a EI of 120 lbs.....

Steve....."and the urge to throw things".... when the transformer weighs so much I can hardly lift it up..... it slows down the urge to throw.... otherwise.... the thought had crossed my mind on a few occasions.

................oztules
Flinders Island...... Australia

Offline MadScientist267

  • Impossible Condition Curator
  • Hero Member
  • *****
  • Posts: 1514
  • Karma: +44/-4
  • Rules? What rules?
LOL I hear ya there... hadn't even thought about the raw weight :O

Quick question on this, as it seems like a good spot to ask it... On the idle losses - Putting the little toroids in series with the EI having the same end result as using a toroid to begin with, I'm understanding that the mechanism is slightly different... the small toroid with EI acting as a HF filter, and less core loss at higher frequencies using just a toroid to begin with... Does this mean that there's more hash making it to the output that needs to be dealt with on the secondary side, or...?

Steve
Wanted: Schrödinger's cat, dead and alive.

Offline oztules

  • Moderator
  • Hero Member
  • *****
  • Posts: 1177
  • Karma: +105/-8
  • Village idiot
The W7 powerstar has EI... and is a great performer... better than the PJ out of the box.... but a ferrite does not stop the 4-500 watt idle current.
I don't know why such a tiny choke makes such a 10 or more fold decrease in current.. but it works with torroids, and high quality iron cored EI. The EI is generally twice the current as the torroid ( twice the steel, twice the magnetic domains to switch back and forth).

But 13uh is not enough to explain very much, so it looks as if it is a switching thing ... don't know.

The hash is the same as far as I can tell, so the output is a composite of all the pwms that make it up... d class amp?

There is a 4uf cap across the output that shapes the wave to a  decent waveform.

.................oztules
Flinders Island...... Australia

Offline oztules

  • Moderator
  • Hero Member
  • *****
  • Posts: 1177
  • Karma: +105/-8
  • Village idiot
Andymack.

An idea for you here.
As you have the aero sharp 2.5, you will be able to do this:


4058-0

That actually has two full 1.5 boxes behind the facia. Once you remove those massive heat sinks, you can chop and bend and fiddle, bolt them together.....until you get something like this.

The power point is there not as the main output, but as an aux output if your working near the thing.

Once you get over a few KW, your best to direct wire, although there is a 25amps output on the unit that can be used for 4kw I guess.. It is a 4 pin amphol fitting I think.... I actually use it for the grid tie solar input..... which I woudn't do without.

The top box will house the 15kw power board and control card, and the bottom box will house the transformer ...... and possibly the solar controller for the 100 amps that the solar can put out .........

I guess that will be part 2


.................oztules
Flinders Island...... Australia

Offline andymack

  • Newbie
  • *
  • Posts: 23
  • Karma: +0/-0
very smart looking  :)

They're certainly good boxes.  To fit the transformer into one box and the electronics in another box is a very worthwhile thought.  I'm looking for more dead,cheap inverters and (beside the transformers) the boxes will no doubt be useful with various electronics I have around the property.  I picked up a little 1kw transformer isolated grid connect unit and if nothing else I'm hoping to use the transformer as an isolation transformer.   You started me onto a dangerous path  ;D

Offline oztules

  • Moderator
  • Hero Member
  • *****
  • Posts: 1177
  • Karma: +105/-8
  • Village idiot
It is done... the stuff it in part anyway... just some hooking up, and now it looks like this.

4060-0

and this

4061-1

Now you will have to get going...

The boxes are drop dead brilliant, and worth a few hundred dollars on their own....... all stainless and aluminum. Aero sharo have come in for some cririsism when they started over in Aust... but I suspect it was poor design and execution by the installers that was the culprit. They have odd voltage range, and stick meticulously to the aus design rules.. the german ones in particular seem not to. I heard an Inspector mention he had never had a Chinese unit fail the islanding tests, the name brand european ones fail the most. So they are the first to drop off because of line voltage or frequency problems.. as they should.

I have run a number of them  for quite a few years now, and never a problem, and very well built too. The only mud that sticks from the comments I have read, is the ones with noisy transformers... and it's true. If you had one in the same room, you'd be unhappy, and you don't get that from the high frequency units..... I'll take low frequency every time... not all are noisy, but enough to earn them a bad name for that alone.

But you end up with lots of stainless nuts, bolts etc etc when you tear them down... great stuff.





....................oztules
Flinders Island...... Australia

Offline frackers

  • Full Member
  • ***
  • Posts: 239
  • Karma: +9/-0
  • If it moves - computerise it!
An interesting idea has come up - the cores I've found so far are not really big enough either with the size of the hole in the middle or the overall cross sectional area. How about rewinding the steel of the core itself and incorporating 2 of the 1" cores into one, starting with a larger inner diameter and then stacking 3 or 4 of these.

I reckon a jig that uses a sprung loaded bearing pushing down onto the steel as its wound to make it tight and the occasional splash of polyurethane varnish should stop it buzzing. A lot depends on whether the steel in the cores is even the correct spec - any ideas on how to test the basic characteristics of the cores?

Is this a really silly idea or what!

I'll retreat back into my cave now...
Robin Down Under (or are you Up Over!)