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Author Topic: PowerJack LF Inverters - AC Coupling out of the box!  (Read 7394 times)
Fionn
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« on: March 18, 2016, 09:45:05 AM »

Hi all,
        Just wanted to let you know that I have successfully AC coupled a Fronius IG15 and an IG20 to a PowerJack LF 8000W inverter, straight out of the box with no modifications.
These are solid and very inexpensive inverters with good spare parts availability.

They have a sketchy reputation around these parts due to a combination of marketing involving scantily clad ladies  Grin and some cr*p products under the same brand.
None the less the LF inverters have a good rep on other forums with plenty of people very happy with them over the long term.

I believe that there is a weakness in them all right,where upon the FETs can be fried if you lose power to the AC input while the inverter is on. There is a warning about this on the label. None the less, if you AC couple and use a separate charger it's not an issue.

There is a mod for them involving adding a ferrite to the input to the transformer, supposedly it drops the no load power consumption down to about 20W and allows it to AC couple successfully. I'll probably do it soon anyway, even though it's coupling fine with my grid tie units, the lower consumption will be welcome.

With a DC and / or AC dump load controller added it would make for a solid and inexpensive off grid installation I believe.

Fionn.
« Last Edit: March 18, 2016, 09:53:45 AM by Fionn » Logged

PV - 2.75kW East, 1.5kW South, 2.5kW West. 3 x Flat Plate Solar Thermal with side arm FPHE on 268L cylinder
fourfootfarm
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« Reply #1 on: March 18, 2016, 02:22:13 PM »

I've discovered the hard way that ferrite cores are very brittle.

Do you know if it has to be a ferrite core? I have quite a few normal EI transformers floating about from old chargers, microwaves etc. Electronics is not a strong point of mine.

I believe one of our illustrious forum members is has been building his own inverter from powerjack boards and large transformers.
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Outback FM60. EPsolar 30a MPPT and a bunch of Tristar 45's. Hodge Podge of solar ~ 4500w. Various generators and 1000ah 24v forklift battery.

Turkish Turnip
marcus
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« Reply #2 on: March 18, 2016, 08:39:15 PM »

yes I think it does have to be ferrite - it's to do with the high frequency switching losses - if you used a normal iron transformer core you'd get the same core losses as you get in the inverters own transformer.

the newer PJ's don't need the ferrite mod as PJ now include ferrites (though you may get further reduced losses by using a better/beefier ferrite).

At some point I may make my own transformer for mine, as the two transformers mine was supplied with are the limiting factor for power/efficiency.

Glad to hear the AC coupling works well though as that's next on the plan for my system.  Smiley
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baker
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« Reply #3 on: March 19, 2016, 08:51:36 AM »

Fionn
can you post diagram of the set up and  pp  dump loads
I got a inverter that packed in and I  gave up on it, might bring it back to life if worth it
 
baker
 
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fourfootfarm
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« Reply #4 on: March 19, 2016, 09:55:40 AM »

Mine does have a small circular ferrite which the wires pass through, there are no turns on it.

I think I will have another crack at winding my own again. Cheapest place I found was RS. Amazingly ordered about about 9pm and got free next day delivery.
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Outback FM60. EPsolar 30a MPPT and a bunch of Tristar 45's. Hodge Podge of solar ~ 4500w. Various generators and 1000ah 24v forklift battery.

Turkish Turnip
Scruff
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« Reply #5 on: March 19, 2016, 04:24:01 PM »

Mine does have a small circular ferrite which the wires pass through, there are no turns on it.

I'd suspect that's a choke. Which is what you want.
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fourfootfarm
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« Reply #6 on: March 19, 2016, 06:14:52 PM »

Excellent, well I don't actually have any grid tie equipment at the moment but getting hold of some cheap MPPT equipment would be lovely. Especially compared to forking out for an Outback etc.
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Outback FM60. EPsolar 30a MPPT and a bunch of Tristar 45's. Hodge Podge of solar ~ 4500w. Various generators and 1000ah 24v forklift battery.

Turkish Turnip
fourfootfarm
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« Reply #7 on: March 19, 2016, 07:46:59 PM »

They don't play nice with MSW on the input either. Though not important if you are going to AC couple. I tried one of our generators on the input and it did sod all. I'll try again when I remember my clamp meter.
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Outback FM60. EPsolar 30a MPPT and a bunch of Tristar 45's. Hodge Podge of solar ~ 4500w. Various generators and 1000ah 24v forklift battery.

Turkish Turnip
billi
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« Reply #8 on: March 19, 2016, 10:27:54 PM »

8000 watt  is a lot  ?     how high is the selfconsumption ?  


« Last Edit: March 20, 2016, 04:36:39 AM by billi » Logged

1.6 kw and 2.4 kw   PV array  , Outback MX 60 and FM80 charge controller  ,24 volt 1600 AH Battery ,6 Kw Victron inverter charger, 1.1 kw high head hydro turbine as a back up generator , 5 kw woodburner, 36 solar tubes with 360 l water tank, 1.6 kw  windturbine
Fionn
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« Reply #9 on: March 20, 2016, 10:22:32 AM »

Billi, the self consumption is around 20W with the ferrite mods, the best I've seen others get is just under 400mA.
The output rating with the included transformers is only about 4000W continuous though.


Baker, I don't have any diversion loads set up yet. I only connected the outputs of the inverters to test it out.
The options are:
1. DC dump load controller on the battery bank.
Current continues to flow back into the batteries from the grid ties & through the power jack.
Simple & effective, the disadvantages are you need DC loads & cabling & you're limited to about 3kW of reverse charging so your grid tie inputs are limited in size.
2. AC voltage relay on the output.
The AC output voltage rises with the battery voltage so a voltage relay can sense this & switch in 1 or more dump loads.
I'd prefer to use a DC voltage relay to drive a separate AC dump relay in order to have more accurate control of battery voltage.
Dumping on the AC side means you can couple as much grid tie as you can dump.
3. An extension of the above, you could use a PV diverter to pwm divert excess exactly what's needed through a triac/SSR.
This would be the ideal & you could set up a simpler voltage relay as a backup.
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PV - 2.75kW East, 1.5kW South, 2.5kW West. 3 x Flat Plate Solar Thermal with side arm FPHE on 268L cylinder
fourfootfarm
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« Reply #10 on: March 31, 2016, 12:59:18 PM »

I wonder if you could use the PWM output from a Tristar/Xantrex to drive an SSR.

This means you'd be using your dumpload based on the battery voltage (more accurate than AC side) and you'd be dumping the power you need to easily on the AC side.

My instinct says no, but I'd be willing to give at a go if someone thinks it will work.
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Outback FM60. EPsolar 30a MPPT and a bunch of Tristar 45's. Hodge Podge of solar ~ 4500w. Various generators and 1000ah 24v forklift battery.

Turkish Turnip
camillitech
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« Reply #11 on: March 31, 2016, 03:34:45 PM »

I wonder if you could use the PWM output from a Tristar/Xantrex to drive an SSR.

This means you'd be using your dumpload based on the battery voltage (more accurate than AC side) and you'd be dumping the power you need to easily on the AC side.

My instinct says no, but I'd be willing to give at a go if someone thinks it will work.

That's exactly what I do on my system, four TriStar controllers paired up, each driving one of these http://www.crydom.com/en/products/catalog/m_cpc.pdf to  a 3kW immersion, when the stats open the DC dumps take over. The 'driver' circuit to actuate the SSR's was supplied by Hugh Piggott, he calls it his 'Tri Star follower' and it's brilliant. If you want to stay all AC then you can add a couple of relays to operate AC air heaters instead of the DC dumps. I stayed with the DC as default in case I had an inverter failure but I do have the optional AC relays, just not got around to fitting them.

Cheers, Paul

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http://lifeattheendoftheroad.wordpress.com/

'Off grid' since 1985,  Proven 2.5kW, Proven 6kW direct heating, SI6.OH, 800ah Rolls, 4.75kW PV ,4xTS45, Lister HR2 12kW, , Powerspout pelton, Stream Engine turgo, 60 x Navitron toobs and a 1500lt store. Outback VFX3048 and 950ah forklifts for backup,
Fionn
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« Reply #12 on: March 31, 2016, 03:51:22 PM »

That sounds cool Paul.
If one is AC coupling the PV input than an (off grid) inverter failure would mean that the charging stops anyway as the GTIs would lose their grid.
I guess the ideal is PWM AC diversion driven by battery voltage as FFF suggests.
I don't think it should be very difficult to put together.

It trips out itself if battery voltage exceeds 60V or goes under 40V(IIRC) so if using flooded batteries there shouldn't be any great risk of boiling them dry. Albeit this isn't ideal as you lose the output along with the grid ties when this happens - it has to be manually power cycled to reset.

I've played around with mine a lot more since, have driven 6kW resistive loads off it without complaint (while getting about 2kW from PV on the AC side & not for long due to lack of batteries).
It also starts an 1800W Aldi AC compressor no issues. Have ran the house off it at night maybe 3/4 times now. No perceptible difference to being on grid.
« Last Edit: March 31, 2016, 05:15:05 PM by Fionn » Logged

PV - 2.75kW East, 1.5kW South, 2.5kW West. 3 x Flat Plate Solar Thermal with side arm FPHE on 268L cylinder
camillitech
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« Reply #13 on: March 31, 2016, 05:32:01 PM »

Hi Fionn,

I've both AC and DC inputs into my grid and the GTI's have the G83 function disabled so I really need an extra fail-safe (4 x 2.7kW off the Tri Stars). Hugh's circuit uses the DC PWM diversion to trigger the SSR, you can see when the PWM is active (green light flashing) that the controller only diverts a few Watts to the DC dumps before the SSR is triggered. This can at times rise to a few hundred but not for very long as if there is a delay sometimes. It's been in operation now for three months and I've been well chuffed with it.

Cheers, Paul
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http://lifeattheendoftheroad.wordpress.com/

'Off grid' since 1985,  Proven 2.5kW, Proven 6kW direct heating, SI6.OH, 800ah Rolls, 4.75kW PV ,4xTS45, Lister HR2 12kW, , Powerspout pelton, Stream Engine turgo, 60 x Navitron toobs and a 1500lt store. Outback VFX3048 and 950ah forklifts for backup,
fourfootfarm
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« Reply #14 on: March 31, 2016, 07:25:05 PM »

I've been thinking along the same lines for a while now and was looking at a simple arduino set up to register when the light goes solid green in the case of the xantrexs (fully charged) and fire a relay to turn on a dump load. I thought this might be better than a simple voltage set up because the controller could be in bulk stage which would shove the volts right up and I don't want to under charge the batteries.

Currently just using a DC dumpload with a couple of wire wound resistors but would like the power to do something useful other than keep the cats warm.

Using AC coupling and a few immersion heaters would allow me to do this without putting too much of a strain on the inverter. Which although its a '5000w' unit seems happiest around 2.5kw

I've had a scour through HP's site and I can't find any info about the tristar follower I am afraid.
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Outback FM60. EPsolar 30a MPPT and a bunch of Tristar 45's. Hodge Podge of solar ~ 4500w. Various generators and 1000ah 24v forklift battery.

Turkish Turnip
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