Author Topic: Building a 6kw pure sine wave inverter using power jack boards part1 transformer  (Read 60036 times)

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oztules

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Neil, we will effectively be winding a 30-32v:240v transformer... even a straight 8:1 ratio will be fine..... ... seems strange I know, but you have a massive variance in input voltage ie flat batts can be as low as 45v, and full may be 62v.... so you can see it is no point winding for 48. So we wind for the worst scenario, and with high power, give it even more  head room.... so 30 odd volts is what we want.... so to stop clipping at low voltage, and allow for less than 100% duty cycle, we are well below 48v.

Clockman... looks very good. It is a much more efficient way to do transformers this way, than doubling the number of transformers to share the load like PJ do... you use at least 25% less copper for the same turns.

It does not really matter too much whether the turns are bunched or spread, so long as they go through the hole, we will be happy. If it is neat, then your likely to have very low inter wire voltage, and the epoxy will negate wire rubbing , so you can then be happy with the breakdown voltage of the lacquer being over kill..... should be fine.

Measuring the secondaries..... well the system does work, and if you are even only 1 turn out, you will see it easily. 1 turn difference is a huge problem for tight transformers like this, and would create high idle currents due to the tight magnetic coupling. Looser coupling like EI transformers would be less dramatic, and probably absorbed into the other losses more readily.

To get an idea of your copper requirements... if you use 50mmsq for the primary, them 50/8= 6.25mmsq will be a balanced secondary.... ie 2 in hand 1.8mmm will be 5mmsq, and 3 in hand will be 7.6mmsq... so three is over optimal, 4 is over kill ( which I'm not against by the way), but for way way less than 100% duty, you will have created a monster for sure..... put your Sunny Island to absolute shame I suspect.

"so if I did a triple core then winding it has to be done by hand bobbins, I think.".... I have done a triple core as well, and it is painfully heavy to work with.... but gee I like the less turns.......



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

« Last Edit: July 11, 2015, 04:34:34 PM by oztules »
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clockmanFRA

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Thanks oztules for the clear information regards the bunching up of the wires, and the explanations on the  testing each winding for matching each other, the design concepts and ratios and copper used.

I have just finished the 4th winding of 1.8mm diameter wire with 118 turns. It got tight, with 10 wires having to double over, but I managed a card jig of my 14turns 50mm/2 of the primary and put the 1.8mm wires in the spacing's.....  Knowing my luck they wont be perfectly spaced but I have only used 5 out of the 14 spacing's.

Yes, the last winding leaves a 62mm diameter hole through the toroid. phew......

Question..... any tips about wrestling with 6 meters of 50mm/2 ? Out in the garden/field how many rugby players required.? Did you start at half way and wind each way?........What about wrapping the toroid before the primary goes on ?

Picture ... shows the simple winding testing 220vac light fitting, yes it works well. That PVC/plastic solid rod, I use as a resin pusher downer and just roll it around before the epoxy sets solid.

8932-0

Picture..... The Powerjack 10000w 48vdc 220vac Inverter I purchased on fleeway. One of two Inverters toroids being stripped down for bits. These are the biggest PJ do as they only just fit in the case..?
Primary.... 14 in hand of 1.8mm diameter with 18 turns.
Secondary.... 2 in hand of 1.3mm diameter 4 layers, each layer of about 152 turns.
Core ..... 155mm diameter x centre hole 80mm diameter and 75mm high.



My toroid transformer with its final 4th secondary, all epoxy resin-ed and drying/setting.
The plastic bobbins are now a compact size and the last winding left me with 2 twisted/soldered joints.
The little card jig with the 14 primary windings showing, so I could space those 10 off secondary's.
4 copper 1.8mm diameter wires, each is one complete turn for each layer of windings, so I know how much I am using.
The core of the PJ toroid, look at that, they have rounded the sharp metal corners? 

8934-2

« Last Edit: July 13, 2015, 12:54:45 PM by clockmanFRA »
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oztules

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Just a brilliant job Clockman.... 4x1.8 secondary is quite a monster.

Good to see the windings of the power jack. If you joined them together, it would appear that  150 turns secondary and 18 turns primary would give you a decent little transformer too, and 25% less wire.

It is comforting to see their turns ratios, as they are the same as ours..... about 8:1 ie they have 37ish  turns on the primary and 300ish on the secondary  ( series parallel )

Yes wrap the secondary with the tape... so it has at least double insulation.

Start your primary half way through... and I used hand clamps to hold the cable tight into the center and elsewhere, otherwise it is very difficult to get it to form neatly... so clamps and a hitting tool to GENTLY shape the corners.....

Your epoxy on the last layer can be a lot more generous, and it won't be a bad thing if it shapes the ends to a cylinder instead of the wire defining the shape.... I let it sit on the plastic, until near set, and cut away the excess so that the wire is almost completely immersed in the epoxy at the ends.... protection from me bending the primary too forcefully.

Once you wrestle the primary on, you will have one of the best transformers you can get for these purposes. Powerful, silent, no chance of wire rubbing... it should last forever.

curiosity... why did you destroy the PJ's you bought, I would have thought you would have left them complete for lightweight spares etc.


.............oztules
« Last Edit: July 13, 2015, 03:58:58 PM by oztules »
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clockmanFRA

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Thanks. more epoxy it is then!

With just its 4th winding, my 'Oz Animal Inverter Super Duper' is 28kg....... and I notice at this weight the transformer it self when just resting on the table, can easily damage the wire enamelling/lacquer.

The locals around here think I am already stark raving bonkers, so watching this mad chap wrestling with 6 meters of black cord, in the middle of the field, on a work bench, with appropriate machines/cars around as temporary holding equipment is going to be most entertaining.!


"curiosity... why did you destroy the PJ's you bought, I would have thought you would have left them complete for lightweight spares etc."

I purchased the 10000w and the 8000w, PJ's for not much money. I really struggled getting any decent size toroid cores from old PV GTI's.
 Originally I was going to use the 10000w PJ toroid's and do a Oz inverter on them, and leave the 8000w PJ alone as emergency backup. But upon opening the PJ 10000w case, I realised that the PJ cores were not that big, and I was going to struggle with the small core size, 155mm diameter, 80mm diameter, 75mm high, 7.5kgs.

 As the 10000w has the same boards as the 15000w, minus 2 caps and a few component changes, I dedicated the 10000w as strip for spares. Especially as a BILL has just arrived, a month later, from the French Government demanding 40euros for Importing from China those PJ 15000w power boards stuff.

However, now I have that 'OZTULES CONVERT & MAKE' ailment, warning highly contagious.
 
 5 days ago I thought, "Hmm perhaps I could do a conversion on those 2 PJ 10000w toroid cores."
And I had just run out of mylar tape for my 'Super Duper', used about 400 meters, very difficult just getting small quantities quickly here in rural Normandy. In the UK in a couple of weeks, so I can call in at the firm that made my toroid cores 2off 190mm diameter, 90mm diameter and 60mm high, .... http://www.airlinktransformers.com/bespoke-built-transformer-service/ .... and pick up stuff. ;D
 
So the 10000w PJ is no more, Arise my 2nd 'OZ Super Duper' . he he.................





« Last Edit: July 14, 2015, 02:29:23 AM by clockmanFRA »
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clockmanFRA

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Been on a short break with my youngest 8 year old, and doing some work.

14 turns of 50mm/2     .................

I have hooked my winding bench to my trailer, and away I go......

9001-0

Completed, phewwwwwwwww.

14 turns, 50mm/2,  through the centre equals exactly 6 meters, tum te tum, that was very close  ;).



Oztules , what do you do about wrapping and fixing those 14 turns with?

Thanks.

Everything is possible, just give me time.

oztules

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"Oztules , what do you do about wrapping and fixing those 14 turns with?".......... errr.... nothing.

The rubber bottom and rubber top washer and steel " washer/plate" stop all movement....

Nice to see some one else suffer instead of just me..... ;)

Thats a serious transformer, and will give years of service at high power....never mind inverter usage only.

Well done........ too well done actually.... I've been out gunned ..........


Whats the voltage on the primary,  now with 240v on secondary??


..............oztules
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clockmanFRA

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Warts time.

Making that extra 4th 1.8mm diameter 118 winding left me on paper, just enough space to get 14 turns of 50mm/2 through the centre hole and lay tidy, in theory.

Nope it didn't work out, so I ended up with the 14 turns with 1 and a 1/2 turns overwrapping itself.  ::)



However, I spent some time re=reading 'oztules' notes again.......
 "To get the thick primary in there... 14 turns will be difficult, maybe more iron, and less turns will allow you get to a stage where the turns are possible with the smaller hole you have.... note my photo. 14 turns of wire took up the whole hole with a single layer.... more would have made it messy, and hard to get a bolt through to hold the thing down."

9004-1

I still have enough space to get a bolt down the middle of my toroid, and I read this........
 "Remember, a turn is counted as a wire going through the hole. Don't care how it ends up, but has to be through the hole... that's where the magic happens. So this takes away the confusion of half turns at the start or finish.... if it goes through the hole, it counts as 1 turn. If you only count the wires in the core, you will be fine."

And a photo of another 'oztules' torroid with more turns and some overwrapping through the centre hole...


So I think my toroid will be okay.?  :-\

I also read this...... " Don't epoxy the  75mmsq cable... not necessary in any way. It is both silent because of the sheath, and vibration is not a problem for the same reason."
So no need for me to wrap and lock those 14 turns, although I just recently obtained some spare Potting compound used in underground Big cable junction boxes.
At the same time I obtained some 50mm/2 straight through connectors and I solder those.

 My first Pic of my toroid above, shows a joint on the last turn of my 14 turns, as although I started winding half way I ended up with half a turn out.  :'(

I will use 50mm/2 Tri rated/car battery/welder flexible cable for the bit from the toroid to the PJ Boards.

Everything is possible, just give me time.

clockmanFRA

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"Whats the voltage on the primary,  now with 240v on secondary??"

I have just done the test.

220vac and light bulb on the 118 turns x 4off and 165.9vac going in the secondary.

9006-0

And meter attached to the 14 turns, primary is 19.65vac.

9007-1

Everything is possible, just give me time.

oztules

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Once you get the thing going, short the light out so you can drive the secondary with the full 240/220v. You need the light to get it going, after that it will draw almost nothing direct coupled to the mains...... very doubtful you will get it going without the globe in series though... inrush current is huge for these things anywhere near zero crossing conditions.

................oztules
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clockmanFRA

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Yes, thanks for that 'oztules'.

'IT LIVES, IT lives I tell you'.... well once the secondary was taking the full 236vac, it was very very quietly softly humming.



The primary 14 turns was showing 28vac.

9009-1

Hmm, Not sure if that's good or Bad?
 You did say " so 30 odd volts is what we want.... "
« Last Edit: July 29, 2015, 11:07:26 AM by clockmanFRA »
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oztules

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one more turn would be better, but it will be fine as it is.... you will do better with flat batteries :)... you have more head room.

Your cores are slightly less cross section than mine from the looks. I would get 2.28v/turn, your  getting 2.0... so your actually running a 118x2=236v transformer.

I fully expected your cores to be bigger/better than my chinese ones... but not so.

The idle current will be interesting to see when you hook it up. It should be ideal for 220v use, as it will be further away from saturation then...... mine are 240v units, so you may have hit the right turns for 220v.

Next....... lets see what she'll do mister :) :) :)

Don't forget to use the ecore ferrite filter... you should do around 25-30 watts for a monster transformer and electronics draw..


......oztules
Flinders Island Australia

niall2

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i,ve no idea technically whats going on here but its fascinating to watch .....good luck Clockman

clockmanFRA

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i,ve no idea technically whats going on here but its fascinating to watch .....good luck Clockman

Thanks niall2. I sort of see the principal and concept of the 8 to 1 ratio and how the mass of the toroid core is significant.
My manufacture in the UK could only go to 60mm max height/thickness.

I think if I was doing another, I would go for 3 toroid cores at 60mm thick but with 200mm od and a 100mm centre hole instead of my present 190mm diameter and 90mm hole.

But I feel sure the 'OZ animal Inverter' that I am building with the maestro's guidance, will do what I want, and put the SMA SI6 to shame.


Everything is possible, just give me time.

clockmanFRA

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one more turn would be better, but it will be fine as it is.... you will do better with flat batteries :)... you have more head room.

Your cores are slightly less cross section than mine from the looks. I would get 2.28v/turn, your  getting 2.0... so your actually running a 118x2=236v transformer.

I fully expected your cores to be bigger/better than my chinese ones... but not so.

The idle current will be interesting to see when you hook it up. It should be ideal for 220v use, as it will be further away from saturation then...... mine are 240v units, so you may have hit the right turns for 220v.

Next....... lets see what she'll do mister :) :) :)

Don't forget to use the ecore ferrite filter... you should do around 25-30 watts for a monster transformer and electronics draw..


......oztules

I could get another turn if you really do think it would help, but as you say 'France' is supposed to be 220vac.

I will check back to you before I fire up the PJ boards on a bench test, and post some Photos of my connections and to what and where, for you look see.

The Secondary connections on the board seem numerous.?

I will look in the PJ 10000w to see how the basic cables go as the boards are the same, but the transformers are series connected.

Several folk have commented on the centre Bolt that holds down the transformer, any particular cautions, when I eventually mount it in my Inverter Cabinet?

Ecore ferrite filter, on the DC + or -  cable ?

Fuseing ? I have this 250a on the DC side, okay? Any more fusing anywhere?
9010-0

Sorry for the simple questions, but all knowledge/help is very gratefully received.
Thanks.

Everything is possible, just give me time.

oztules

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The mounting bolt is to be treated as a single very high current turn... in this context, that means nothing may allow a circuit to form between the base/chassis and the top of the bolt/plate. If it does, high current will flow in the bolt and we don't want that.
.
I also use plastic pipe or heat shrink on the length of the bolt so that there can be no interference with the wiring jacket on the primary...... just a useless precaution... but I do it anyway.

The ferrite can be on any of the two wires going to the transformer primary.

The 10kw unit will give you the wiring.... use the fan out of it, as it is "special", and the board will need to see it. The board uses the feedback pulses from it to moderate the rpm... if it can't see that it assumes failure and will shut down when it tries to find it... will run till then.

A normal fan will work if you get a 2k2 resistor and place it on the pulse line to the fan stator, and that will act as a timing pulse, and the PJ will be satisfied. I use beecroft fans as they lend themselves to this modification.

Beware of three wire fans on ebay, some have been found to not have a true tacho circuit on the third wire, and the plugs won't fit either... will need modding.

You only need transformer secondary to board, and board to output point. The other 220v point is for shore power inputs.

The rest of the wiring is just fan and temp probes..... and the 10 wire harness.

Fusing is only to protect wiring, and will not protect the inverter.. 250 amps should be fine, as it won't blow until it sees 500amps or more in the very short term. ( maybe a second or so). Assume wiring is in the > 50mmsq range as well. ( I run 3 x 35mm equal lengths to battery case... one for each string)

I also have a big RCD on the 240v output.... I like leakage detection.....

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

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lifer

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That's a real hardcore project you've done (both master and apprentice)! I payed good money for a commercial version (though mine looks bigger/heavier, though it's 5kW rated).

Anyway, I heard you talking about casting it in resin, to reduce noise/vibrations so I kindly ask you to recommend some good resin to do the job.

I prefer to cast it as a big (flat) cilinder with a inner hole, with minimum wall thickness of 1-2cm all around the transformer.

The problem is I don't want to affect the cooling capacity thus I wonder which specific resin to use (with better thermal transfer).

Thank in advance for any suggestion and sorry for disturbing your great tutorial.   

oztules

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I use west systems.... as I was given 25 liters of the stuff.

We are only using the epoxy for noise and wire stabilization. If you have a commercial torroid, it will likely not have good separation between wires.. these now do.

Just dunking it won't help you unless you can vacuum it at the same time.... and then keep the epoxy as minimal as possible, or you will cause heat build up in the thick epoxy.

I have found that all torroids so far ( commercial) do not take the time to try to separate emf potential in one wire from the next, they aren't soaked in lacquer and cooked.... and so fail regularly from internal shorts.... very sad really.

This technique stops all of those problems from being able to happen... if yours has a larger ( >60 lbs torroid) it is really  a lot better than 5kw at 100% duty cycle ( if the steel is any good and it is a torroid).

..........oztules
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lifer

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My commercial transformer was custom made: OD=310mm, ID=120mm, H=110mm, W=39kg (85 lb), 16/125 turns, 30V/230V, high-quality "japan made" silicon steel (according to mfr).

It works OK but I could hear some random noises (vibrations) during normal operation and I thought I could make it dead silent somehow.

Is that west systems epoxy resin thermoconductive/elastic by any chance? I'd like to cast it like a monolithic block but I'm affraid of further cracks due to wire/core thermal expansion or something.

Do you think I could just soak it in lacquer to attenuate those vibrations? Or should I put it between two thick aluminium disks (for better cooling) then squeeze them hard (using some soft rubber sheet in-between)?

clockmanFRA

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Hi lifer,

I used this epoxy, I only used about half,   ........ http://www.ebay.co.uk/itm/370552815307?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT ..which is thinnish viscosity so runs around and in between the wires on each wrap. Takes about 4 hours to get sticky and 12 hours to set. I also used the ordinary tube stuff that is thick for a few jobs sometimes.
Everything is possible, just give me time.

clockmanFRA

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Ozutules, sorry that centre bolt again.... I have a suitable Stainless steel bolt but its non magnetic, so not sure if that would be okay, ? and not cause problems where it touches the 2 holding discs?

I have a strange black wire coming out of the new 15kW Control Board that's not on the PJ 10000w Board.
9012-0

and on the back of the PCB, I think this wire goes to the battery 48v negative connection?
9013-1

Thanks for the Fan information, I did wonder why 3 wires.
Will I need those 2 heat sensors connecting in, ? they just work the main fan.
The other 2 fans on the PJ 10000w are just heat sensor tripped direct from the 48v battery connections.
Everything is possible, just give me time.

clockmanFRA

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Okay .. the connections on the PJ 15kW Power Board and control Board.

Is this okay oztules.?

Control Board Connections.

9015-0

Power Board. The heat sinks have threaded holes for fastening your cables.

9016-1

Another question 'oztules', Does it matter which way the Primary is connected onto each part of the Split Heat sink. ?

And there's that mystery wire again.
Everything is possible, just give me time.

clockmanFRA

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The Fan heat sensors on No2 toroid transformer from the PJ 10000w.

The left larger one is dumb connected to the 48vdc battery connections and just switches the other two fans on.
Hopefully I can borrow the other one and the smaller one.



This heat sensor comes ready attached to the Primary heat sink.

9018-1
Everything is possible, just give me time.

oztules

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Your connections all look good. The black eye to neg..... I think it solves the over voltage problem, as when I did that, i no longer needed the zener.

The only fan that counts is the primary one., I use a separate circuit to activate my fans, and just have a dumb little fan with tacho wires to satisfy the board, but all cooling is controlled separately for me.

Wire co-ordination is moot unless you want to try the suicide shore power charger..... that required syncing the input to the output..... but if you don't use the charger, then makes no difference that I can ascertain.

For those wanting the charger... I used a 10amp fuse in the line output from the transformer to the board, connect shore power, and the fuse blows or runs fine as a charger.... if it blows, then reconnect the N and L wires from the secondary  back the front and try again.

It does not use cycle by cycle limiting from the secondary for control, so it makes no difference as a stright inverter......, but it does need cycle by cycle control for syncing the shore power to the fet gates for charging usage.

The center bolt can be any material you wish.... but if it is conductive in any way, treat it as a single turn high current winding.... keep it open circuit... ie nothing in the box may touch the top of the bolt/washer, or you will make a connection of the 1 turn.... and gee it will have some serious current attached to that 2v potential....


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

clockmanFRA

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Again, many thanks 'oztules'.  If you were closer I would buy you a Pint of our local Brew.
Here being advertised by our Cat, Kiwi, (sorry name was a coincidence).
The Family Hubert's just live 8 miles away, good friends........http://www.lesvergersdelamoriniere.com/



Thanks, Black eye to neg... it is, nice to hear that 'PJ' are listening to you.

If I can lift those temp sensors and re-use, I will.  However I will be fitting a temp sensor and switch to switch the other 2 spare fans on, maybe.

No, I will not be using the PJ battery charging facility, but I like your fuse concept for Synchronisation of the HZ with other sources.

Thanks about the centre bolt, it becomes an extra turn if something touches the top......got it.
And yes I have a suitable plastic tube to shield the bolt.

AC Coupling.
 Using used/second hand GTI's, (very very cheap), all SMA as I have Grid guard codes to alter their parameters. These GTI's are taking PV and are connected into the 220vac Mini Grid that the New Inverter is creating, and which the House's, Buildings are using.

Now what I understand from your last comments..... That the new inverter can take backfeed from the GTI's and this can go backwards through the transformer.?
I have done your test with 220vac on the secondary and producing 28vac at the Primary so I see that.

......But this will be AC at 28v. ?
......So its unlikely that the batteries can be charged.?

Battery charging using this Inverter is not required by me as I have plenty of Battery charging sources, 3off 3.7m (12 footers) wind turbines and 5kW Pv on trackers, these are controlled by 3 Tristar Dump/controllers a Tristar MPPT controller and a Midnite Classic 200. The Midnite Classic has 2 aux relay outputs and these can be set to switch on and off depending on the battery voltage. (I love the Classic as its just so good with its charging regime).

I also have a real sweet used/second hand ELTEK 220vac IN, 100a 48vdc, battery charger installed, that can be used if all else fails, ie no SUN and NO WIND.
 In certain conditions this also could be connected to my mini grid and use excess power from the GTI's.  I find that I get a good 10% of PV rated power from my Mono Panels on even gloomy days, ambient light.
Modern GTI's are reasonably efficient so with say 15kW of PV I would still be getting about 1.5kw on those murky days.

Okay raising the HZ frequency to back off/shut down the GTI's is a NO NO, why? because I have a SMA Sunny Island 6kw, actually only rated at 4.2kw continues use.
 And the Frequency Control is very flaky and with me goes up to 60Hz, with not so good consequences. Yes I could get around this, but by totally installing very expensive SMA ancillary equipment, which I will not as this defeats the Self Build/empowerment concept within me. 

Now what I recall you said, "If the GTI's power is not being used, the 220vac voltage from the Inverter increases" or something like that.

Do you recall how much the voltage increase is before things start to get 'hairy' and what increase do you think is SAFE, (without damage) that this Inverter PJ boards can take?
As I can set the GTI's to shut down at say 245vac or whatever.

Now my 5off GTI's are/can be up to 500 feet away from each other and my main Power station Building, so I promised the Mrs that "I shalt not dig any more Trenches",  Sigh, so no way of getting signal cables to the GTI's.
 
 So I will also need some sort of simple PowerLine control to shut down the GTI's when power is not required, but I will separately post on this forum about that.

Yet again, a big thanks to 'oztules'.

I am awaiting some more 50mm/2 flex cable for final hook up, so a few days before I switch the baby on.
 
 
« Last Edit: August 01, 2015, 03:36:58 AM by clockmanFRA »
Everything is possible, just give me time.

oztules

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..... yes the batteries will charge up to their 60v or more from the grid tie..... not 28v... I 've had many kilowatts going in via that avenue.

The AC will rise when the batteries get full, and no longer create a low impedance to the line input.... if the house load is insufficient to burn it up, then the grid tie will try to push the AC voltage up...... how far????.. as far as the upper voltage is set for the GTI.

250v is fine for a 240v system, and in fact 10% ( 22 or 24v)  is fine really for almost any appliance you can think of.

For a 220v system, 240v is probably the upper very safe limit... maybe 245v.

Yes.... this means remote control of the GTI's is possible using voltage not frequency.... which we cant change anyway. If you have the control codes, then simply set them a volt or two apart, and stagger the release... this way you can drop them off sequentially.... sounds like a plan. My aero sharp GTI's do this as they are programmed slightly differently, so one drops out before the other by only less than .5v difference at about 250v or so from memory. I also have a relay built in the inverter to shut down the GTI from battery voltage.... it is not used anymore.... but there if I want to use it.

All good fun....



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



Flinders Island Australia

clockmanFRA

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That's 'the icing on the top of the Cake'.  :)

..... "yes the batteries will charge up to their 60v or more from the grid tie..... not 28v... I 've had many kilowatts going in via that avenue.

The AC will rise when the batteries get full, and no longer create a low impedance to the line input.... if the house load is insufficient to burn it up, then the grid tie will try to push the AC voltage up...... how far????.. as far as the upper voltage is set for the GTI"
.


Sorry a bit dim at this end........just to Clarify........

So our New Oz Inverter and PJ boards will handle the GTI's and any spare power will infact at first go through the transformer and PJ boards and charge the batteries. ?

Then as the Batteries fill up, or are fullish, the AC 220v Grid that our New OZ Inverter is creating will raise the AC voltage on the said New Mini Grid?

If the above is correct, then ........... My head contents will need updating to understand how AC will push DC batteries, or are you fitting a rectifier somewhere. ?

Yes, I can set all the GTI's to sequential shut down as  the voltage rises and bam! they shut down fast. Starting up again takes about 20 to 30 seconds or so, but meantime the New Inverter can cope short term yes?

If I happen to have say 10kw of PV on GTI's kicking in and feeding the buildings, because of high power use, have you any idea/rough ballpark figure,  how much GTI power the New Inverter can take being back fed and for brief time period so the PJ boards survive, perhaps max 15kw. ?

If need be I can limit the installs of GTI's on this New Inverter accordingly.

 I will check with the GTI's software to see what voltage shut down I can come down to, as you say 240vac should be seen as Max voltage rise.

What does the PJ boards normally put out, exact 220vac or does it wander a little depending on load.?

Yippee, a Plan is coming together..........


Everything is possible, just give me time.

oztules

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The inverter will handle significant power in the reverse feed.... wish I knew how much, but 8kw should be in the can do part, and higher for shorter periods. Remember they claim 250 amps in charge mode... so maybe 12 seconds at 12kw???

You will need to keep the GTI's back feed around and below a C10 charge for your batteries.... The PJ has no idea this is happening so will not regulate charge

The H bridge switching mos fets will synchronously switch the DC back through to the batteries from the AC from the grid ties... in the same way it switched the DC to quasi AC. ( @ >20khz or more )

This rectification is very much more efficient than diodes, as the silicon band gap is not there so you don't loose over .6v in the diode before you start...., instead the fets look like a short circuit at 3.7milliohms/6... or  .6 milliohms... so current x  .0006 gives the voltage losses... and so  .06v x 100 amps or 6w per 5kw in the bridge arms.... very impressive... then some switching losses, but still seems pretty good in this format. ( or I^2 x R  is 10000 x . 0006 = 6w per 5kw for 100 amps)

Looking at the scope wave forms, it seems to switch 80% on in 50ns... so losses are not too bad really.

"So our New Oz Inverter and PJ boards will handle the GTI's and any spare power will infact at first go through the transformer and PJ boards and charge the batteries. ?"...... yes........ any power not dissipated in house loads will revert to the batteries.

"
Then as the Batteries fill up, or are fullish, the AC 220v Grid that our New OZ Inverter is creating will raise the AC voltage on the said New Mini Grid?"
... yes as there is no battery load, the AC will rise, as in a normal GTI to grid format. A concentration of GTI's in a street on a single pole transformer will push up the local grid voltage if the sun is out and the systems all run. This will give it a higher "gradient" to run back to the power station/general grid.... ie more power has to go somewhere else or the same place faster.

As a general observation, if you have 15kw coming in, and the loads don't match, the voltage will move to compensate.. setting the GTI's will give you a bang bang regulator. More and smaller GTI's will give better definition I suspect. The wiring to each house in the minigrid will also have voltage differentials locally.. this may help too.... it will depend on the wire size , run length and GTI power. Maybe 1.5kw per house will be enough to be more than useful.

"What does the PJ boards normally put out, exact 220vac or does it wander a little depending on load.? "

It wanders around the set voltage by maybe 5 volts generally very close to 240v for me. Our regs require 3 minutes of clean power before the GTI reconnects... the SMA probably do what ever they please ;D


................oztules
« Last Edit: August 01, 2015, 09:00:40 AM by oztules »
Flinders Island Australia