Aurora Grid Tie

[ruairihev]

Hi,
I have built a few 24V battery charging 12ft wind turbines that are all working fine. I now want to build a grid tied version using the same design except of course for the stator. Going to use the 3.6Kw PowerOne Aurora Grid tie inverter. The inverter has a DC Voltage range of 50V to 600V. Should I then wind my stator to cutin at 50V or should I wind it to something higher and program the inverter to cutin at that voltage?

Parts List:
25x50x10mm N40 Magnets
400mm rotors
19mm airgap between magnet faces (can maybe make this 17mm)
3.6m diameter
6.5 tsr
16 poles per rotor
12coils
star connection

I can fit 130 turns of 1.32mm copper wire per coil into my stator, possibly 140 if I'm more careful with the winding. (one in hand)
I did a test coil and after applying a few equations worked out that I'm getting 60Vdc at 120RPM. 120RPM is the cutin speed that I was working towards. Should I stick with the 130turns and use the programming to set the cutin at 60V or higher or should I be looking to wind more turns into my stator with a smaller wire?
I have a large roll of 1.32mm wire which is why I wound with that gauge. (similar to #16 gauge wire)
The less turns of bigger wire the better was my understanding but not sure how it effects things when going grid tied.
Any help or suggestions are most welcome.
Thanks,
ruairihev

[Flux]

I can't help with the programming for the inverter but I suspect you can program it for any voltage, in which case the simplest approach is to wind for a cut in voltage that will not exceed the peak inverter voltage in a high wind before it comes on line. That way you will save the cost and complexity of a clipper.

If the inverter can take 600v maximum then you need a cut in below 100v to be safe without a clipper. Bearing in mind that furling will be ineffective on no load you will be looking at near runaway speed if it comes off load in a high wind.

There may be some gain in efficiency if you wind for higher voltage but only if you have a lot of line resistance will it make much difference so I think your proposal looks sensible.

If you want the higher efficiency then winding for about 150v would help but you would then almost certainly need a clipper to be safe in all wind conditions.

You may be advised to check that the inverter doesn't have to be de rated if you confine it to lower voltages. In fact with a 12ft machine matched decently with mppt you will need to furl early to keep within the 3.6kW so this voltage issue may be important.

I hope someone familiar with the inverter can give you more advice.

Flux

[Rob Beckers]

Hi Ruairihev & Flux,

My business imports and distributes Aurora inverters, and I've been doing that many years, so I know 'm well...

Power-One specs a minimum of 200V DC for full output power, for the 3.6kW wind inverter. So I would shoot for at least that much. Cut-in can be anywhere above 50V.

For a 12' diameter turbine, assuming reasonable efficiencies, you can expect 3.6kW out to the grid at about 12.5 m/s wind speed (if your alternator can handle that). Cut-in for such a turbine would be around 3 m/s, with about 50W out to the grid at 3.5 m/s wind speed. Since voltage is approx. linear with wind speed; if 12.5 m/s corresponds to 200V DC, then 3 m/s works out to 55V as the starting voltage.

That gives you the lower boundary. Should you go that low? Personally I strongly believe in a fool-proof mechanism to keep RPM under control, not just by furling, but by adding dump-load resistors at a certain voltage and possibly by disconnecting the inverter if a set value is reached (an Omron measurement relay plus contactor will do so very reliably). Even if the maximum working voltage is 'only' 200V DC. I've had to deal with too many broken inverters that were fried due to overvoltage (not covered under warranty by the way), and a factor of 3x is not much for an unloaded rotor to speed up. Keep in mind that the 200V working voltage is loaded. When unloaded that becomes closer to 250V (or more, depending on the stator resistance), so your margin of safety may not be all that great.

In short, rather than shooting for the lowest voltage I would target a voltage where stator losses are reasonable. Heating goes with the square of the current for the stator! Even if that means a higher voltage. In practice many turbines shoot for around 300 - 350V DC at full power, and incorporate good overvoltage protection. Low or high, either way will work fine as far as the inverter is concerned.

I don't know what the design TSR is for your blades/turbine. Assuming it's around 7, then 3 m/s would correspond to 110 RPM. Of course, it's always possible to program the inverter to run the turbine at a slight overspeed in the lower wind speed region, and go towards optimal for mid and higher wind speeds. That's the beauty of inverters where you can program your own curve.

What works best in terms of voltage/wire for the stator would need a few calculations: If you can get twice the windings (double the voltage) onto stator coils, and double the resistance in doing so, the effect would be half the stator current, and half the heat/losses in the stator (losses are I^2 * R, with I half and R double the original values that makes 1/4 * 2 = 1/2). From that perspective going with a somewhat higher voltage than the absolute minimum can have advantage.

Hope this helps!
Shoot if you have any other questions.

-Rob-

[Flux]

Thanks Rob, that information is very useful.

Personally I agree with you about some form of turbine speed control but many will no doubt try with furling. Furling is fine on load and with batteries where it never becomes disconnected there is no issue. With grid tie I am not in any way happy with furling machines going open circuit. The problem can be solved with a load control that loads in place of the inverter but it adds cost and complexity.

In view of this I would aim for running at the 200v for a non speed controlled machine if that will give the full output from the inverter, you then have more headroom for over voltage off load.

There is only one issue that I am not in agreement with and that is the bit about machine efficiency and stator heating. For a given size of alternator the stator heating will be the same for the same power out irrespective of the voltage it is designed for. The same is not true for the connecting cables and the loss there will be higher with lower voltage.

You can push more out of any given stator if you raise the voltage as long as the available excess volts are there for a given speed but at the design voltage for a given speed the loss will be similar. A low voltage winding will have fewer turns of thicker wire and will have lower resistance, it is true that loss is proportional to I^2 but the resistance will be lower in the low voltage machine and will compensate. There will be less diode loss at high voltage but at 50v and beyond this is no real issue. Things are rather different at say 12v where the physical restrictions mean you may not be able to wind the machine effectively  but this is an extreme case.

With speed control I agree that it would be better to run near the peak inverter input.

I am surprised that relay change over is quick enough to protect the inverter, that is reassuring but even so I don't think I would want tu use voltages near the maximum without a speed governor.

Flux

[scoraigwind]

Hi Ruairihev & Flux,

My business imports and distributes Aurora inverters, and I've been doing that many years, so I know 'm well........
 If you can get twice the windings (double the voltage) onto stator coils, and double the resistance in doing so, the effect would be half the stator current, and half the heat/losses in the stator (losses are I^2 * R, with I half and R double the original values that makes 1/4 * 2 = 1/2). From that perspective going with a somewhat higher voltage than the absolute minimum can have advantage.

Hope this helps!
Shoot if you have any other questions.

-Rob-

It seems like Rob has answered the question nicely, but I'd like to point out that putting in twice the number of turns in a stator coil will (yes) double the voltage but it will (actually) make for fourfold resistance.  The wire is half the cross section and also twice as long.  So in the end although the voltage is double and the current is half, the loss in the stator is exactly the same.

I'd recommend some kind of over-voltage protection.  There's a diagram of a suitable trip circuit here.
http://www.scoraigwind.com/circuits/overvolt%20trip.htm

[Rob Beckers]

Thanks Flux and Hugh! As mentioned I didn't do the calculations for wire size vs. resistance. That's interesting: So the stator losses are a factor of how much copper you can pack into the space, regardless of voltage and wire size. I will keep that in mind.

About furling: While it sheds wind, and therefore power, it still has some cross-section to the wind and how much it speeds up without a load is a matter of energy intercepted from the wind vs. mechanical losses. You better hope those drag losses ramp up quickly with RPM or it will still overspeed. The 'typical' scenario for blowing up grid-tie wind inverters is where the inverter is online, the turbine running in a fairly stiff wind, power going into the grid, and suddenly the grid falls away. Think of it, chances of that happening are really much higher during high wind events than on a nice summer day with no wind. The turbine suddenly becomes unloaded, and runs away before furling and such kick in. Chinese wind turbines seem particularly good at this...

We've been using an Omron voltage measurement relay, hooked up to a contactor that's wired in a way that if there's no grid it's off (3-phase from the alternator disconnected), and when there's a grid but the alternator voltage goes above the set limit it again disconnects. The shortest delay on the Omron's we've used is 0.2 seconds, the contactor switches in about a dozen ms, in all it's plenty fast enough to disconnect a runaway before the voltage exceeds 600V. It's cheap insurance. The same switching signal could also be used to connect a dump load when the inverter disconnects. The Omron has some hysteresis to it, so it is not chattering constantly.

-Rob-

[Ungrounded Lightning Rod]

Thanks Flux and Hugh! As mentioned I didn't do the calculations for wire size vs. resistance. That's interesting: So the stator losses are a factor of how much copper you can pack into the space, regardless of voltage and wire size. I will keep that in mind.

Yep:  How much copper and how much power you're pulling, presuming you kept the same total cross-section of copper by adjusting the number of turns and the wire size in proportion.

The wires down the tower and over to the inverter are a different issue:  You can adjust their cross-section in proportion, so that doubling the voltage saves you a factor of two in amount of copper and a bit less than that in cost of the wire.  Or you can leave them alone and cut your transmission losses by a factor of four for each doubling of voltage.  Transmission losses might be significant for a long run but probably won't matter if your inverter is near the tower.

About furling: While it sheds wind, and therefore power, it still has some cross-section to the wind and how much it speeds up without a load is a matter of energy intercepted from the wind vs. mechanical losses.

Most of the drag/furling force on the mill comes from the mill decelerating the wind as it pulls power from it.  When it's free-wheeling the aerodynamic drag of the blades is small.  (You designed it that way:  You want the blades to slide through the air so essentially all your drag comes from the power you captured.)  So your folding-tail automatic furling won't work with the mill unloaded until the wind speed is so high the mill comes apart anyhow.  B-(

Therefore I'd say use your overvoltage/overspeed protection in the "add a dummy load" mode (disconnecting the inverter to avoid overvoltage damage, in addition, is OK *IF* the dummy load is big enough to take its place) and crank up the hysteresis appropriately so switching on the load doesn't make it chatter.  Then your furling continues to happen at the appropriate wind speed.

[jarrod9155]

I can right talk from experiace right now i have a 4.2 aurora running on a 13 footeraxial flux. As for over voltage protection the windy girl has save my inverter from the windmill a couple of times. There is a voltage sensing relay out there but if you lose grid you lose power to those circuits . The windy girl is made to spec mine is set to 400 volts . At that it will short the wind mil till it with in s safe voltage and then release the circiut . My turbine survived a thunder storm with 70 mph winds that came on before the inverter could come on line and the windy girl loaded the windmill and it went in to full furl . I would recomend the 4.2 for the extra 300 bucks my mill has maxed out at 3510 watts so room to grow is good . I got my inverter from Rob he was grest to work with . For cut in you want to be well in to your tsr the inverter turns on at 50 volts and puts on a slight load  so beware of stalling at low wind speeds .

[Rob Beckers]

Therefore I'd say use your overvoltage/overspeed protection in the "add a dummy load" mode (disconnecting the inverter to avoid overvoltage damage, in addition, is OK *IF* the dummy load is big enough to take its place) and crank up the hysteresis appropriately so switching on the load doesn't make it chatter.  Then your furling continues to happen at the appropriate wind speed.

I would like to stress that you cannot rely on the load from the inverter; the grid can and will go down occasionally, it takes time for the inverter to come online after a grid failure etc. So there has to be a mechanism to keep the turbine under control without that load, and a dump load has to be sized large enough to do so.

Regarding Jarred's comment about overvoltage protection not working in case of grid failure: The way I've done these is to have the inverter disconnected (with a contactor that is normally-off in the 3-phase lines from the turbine) in case there is no grid. The contactor gets energized ("on") when there's a grid and the Omron relay senses the voltage is below the set limit. Hooking things up this way makes it much more fool proof (until a better fool evolves   ).

-Rob-

[ruairihev]

Thanks to all for the helpful and interesting comments.
I agree with the need for "extra extra extra just in case the grid goes down" backup protection. I see that PowerOne have an interface box that they also sell which rectifies the AC Output of the turbine and also has a dumpload on/off option. Do you know anything about this interface box Rob? I will definitely have a load to keep the turbine from run away in case of grid failure and will probably go with something like the setup Rob mentioned.

So with the Mppt capability of the inverter the way the stator is wound is not really a big deal, the main issue seems to be matching the blades and the generator and the inverter takes care of the rest?

If I wind with 130turns of 1.32mm that gives me 200Vdc at about 400RPM @ 12m/s which I think is about right for a 3.6m (correct me if I'm wrong). The Line voltage is then about 144VAC. Say there's about 3600W available at 12m/s then the current the stator is producing will be about 3600/(1.73*144)=14A or so. The heat lost in the stator will then roughly be 144^2/1.88=390W (1.88 is the resistance of one phase measured). Chances are that I won't get 3600 watts sustained so the amps shouldn't go much higher than 14. According to a very hard to find ampacity table 1.32mm wire is good for 18Amps (probably reduced by a few amps when wound in a coil). My wire coating is rated at 200degree celcius. So the stator heating should not be a problem, unless my calculations are completely wrong (which they could well be)?

If anyone can see a fatal flaw here then please let me know. I'm sure there are some other equations and considerations that I left out when doing my maths. Otherwise I think I'm just going to go with what I have and see how it works. I also have a reel of 1.6mm wire, if I used that instead then I'd have to open the airgap up to 22mm or so, an option maybe??
Thanks again,
ruairihev

[imsmooth]

I have the same inverter for my 10.5' turbine.  I built a shunt-controller to switch to a 4kw/15ohm load in case the grid goes down.  You can read about it all here http://www.mindchallenger.com/wind.  This web diary/tutorial starts off with a F&P design and then moves to an axial flux.

Pay attention to the section on coil winding/gauge, programming and the shunt controller schematics.  I use igbt switches (you could also use mosfets) with a schmitt-trigger setup.

My inverter is programmed to start producing at 50v, but I only draw a small amount of power.  I used about 12 programmable points.

[Rob Beckers]

Ruairihev, the wind interface box from Power-One does have electronics to switch on a diversion load, it uses an IGBT. However, the voltage at which the dump load is switched on is (semi) fixed at 530V DC. There are a couple of dip-switches to change that voltage, though only "up", the lowest is 530V. For many wind turbines that is too high; by then they are already so much running away that getting them under control at that point doesn't work too well. In practice I don't know anyone that actually uses the dump-load option on the wind box.

The wind box does offer one advantage (if you want to call it that): It will blow before the inverter blows when exceeding 600V. Since repairs on neither one are covered under warranty, it's at least cheaper to deal with a broken wind box than a broken inverter... 

-Rob-

[ruairihev]

Rob,
Just a quick question about your voltage sensing relay and contactor setup for overvolt and grid failure protection; I presume your contactors are energised by the grid all the time and when the grid fails they de-energise and break the circuit. I am just wondering about your voltage sensing relay, has this got a seperate power supply (i.e. a small battery) and if so do you have a battery charger charging it from the inverter or what is your arrangement for this?

Going to pass on the interface box as it doesn't sound like it will do the job for me.

I have the blades, metal work and magnet rotors built and I've started the stator so this project is well on the way. I also got a beauty of a free standing tower yesterday. The power company were moving a powerline onto a new pole as a road is now going where the old one was and I was on hand to take it away. It's 10m high with a 300mm diameter 10mm wall base, going to a 230mm diameter and finally a 160mm diameter. I am going to add another 2m and attach a hydraulic ram at the base for lowering and erecting.

[marv]

Ruairihev,   This is a diagram similar to what Rob was talking about.

Marv.

[Rob Beckers]

The contactor in the turbine's 3-phase lines would be energized through the Omron relay, so it takes both grid power and it has to sense less than the set-point voltage to energize the contactor. There's no special power supply for the Omron, the version I use just hooks up to 120V AC. When the grid goes dead, or the voltage gets above the set-point, the contactor de-energizes and the connection between 3-phase and rectifier (and the inverter after that) is broken.

Note that regular contactors have to go in the AC lines of the turbine; even though it seems more straight-forward to switch the DC before it goes into the inverter most contactors are not rated for DC, or have a far lower current rating for DC  (DC arcs when it gets disconnected, and that arc is much harder to extinguish than it is for AC, so DC rated contactors are rare and special beasts).

Another note regarding Marv's diagram: I wouldn't rectify the AC before hooking it up to the sense lines of the Omron relay. Rectifying raises the voltage, so just measuring AC gives you a little more head-room if needed (before the Omron relay gets a problem with the sensing voltage). Just hook up between two phase lines, if the alternator is wound correctly there won't be much difference between phase voltages.

-Rob-

[nekit]

What Contactor are you guys using to switch off the inverter and turn on the dump load?  I bought a  Telemecanique LC1D18G7 that is shown in the above diagram and it only had one set of normally open 3 phase contacts.  Ideally I would think that it would have double contact, one set open and one set closed, and be normally closed for grind failure.

Thanks,
Rob L

[jarrod9155]

I ran into the same problem . What I did is use the relay as a automatic shut off, if the grid goes down the relay loses power to run so in turn off the input to  the inverter it is safe but the windmill isnt so use the other contacts that are nc to turn on a dump load through a dc relay for a dump load for the windmill .  I also used the voltage sensing relay to activate the dump load durring turn on if the voltage gets to high  . I also have the windy girl  that  is set to 400 volts , It only uses the windmill s power so grid doesnt effect it . The downfall once activated it holds the brake till no voltage is sensed . Hope this helps Jarrod

[Menelaos]

Hi there,

Ich also have a few questions and as Rob and others here seem to be into the details, you might be able to give some advice.

I recently finished my Alternator which is to be used with am Rotor of 6-7 m in Diameter, probably 6.
Here is a link to how I built ist. Its all in German but the pictures may be nice to watch :-)

So now comes the problem:

The stator is wound with 12 coils 200 Turns of 1.6mm wire, connecte in star. After rectifying it gives me an open voltage of 50 V DC at 33 RPM. TSR of the blades is planned with about 6 but it will be adjustable to change TSR. For overspeed protection I will install an active Satll mechanism in the hub using centrifugal forces of the rotor.
Resistance of the alternator is 1.9 Ohms between 2 Phases

I was planning to use the 7.2 KW Aurora to connect to the grid.
I am now a little worried about the voltages.

As I am limited to 16.6 Amps I need at least 400 Volts to be able to deliver full power.
My problem now is that this probably won't happen since the rotor gives this full power at about 10 m/s of wind but even the open voltage will then still be less than 300 V...and I guess that it will drop even more under load.

So what options do I have and what would you suggest?

I could make another stator which would deliver power at even less RPM so that I could use winds of lets say 1.5 m/s (which of course is useless) and reach the 50 Volts then. or set the inverter up to start at lets say 70 or 80 V .Open voltage would then be higer.

But I do actually not see the point of putting more turns of wire to the coils and thus get a higher phase resistance and more losses.

Any Ideas?

Max

[Menelaos]

Forgit to include the link to my Genni 
here it is:

http://www.kleinwindanlagen.de/Forum/cf3/topic.php?t=2851

Max

[clintonbriley]

My business imports and distributes Aurora inverters, and I've been doing that many years, so I know 'm well...

I've had to deal with too many broken inverters that were fried due to overvoltage (not covered under warranty by the way),

Hey Rob, I've been wondering how durable the Aurora inverters are and what the expected lifetime of the units are.

Without overvoltage damage or lightning damage, what is the expected lifetime?

You mention that overvoltage damage is not covered by warranty.  How much have the repairs run?

Is the damage due to overvoltage similar to that from a lightning strike? 
Are they still repairable after a lightning strike?
Thanks,
Clint

[jarrod9155]

I can say so far this has been a great inverter and reliable knock on wood , I believe overvoltage reapair was around 600 bucks plus freight with a omron relay set up you should have to worrie but as far life expectincy not sure .

[imsmooth]

I've had mine for a year without a problem.

[Menelaos]

Those answears to my questions have been a great help...

Max

[Rob Beckers]

Sorry for the late reply; it's been a while since I checked back here...

I've been selling those 6kW wind inverters for 5 years now, literally dozens of pallets to date. So far the only failure I've seen, not due to overvoltage, was a failed USB interface. For the PV inverters the default warranty is now 10 years, and they share the exact same hardware. In other words, the manufacturer (Power-One) believes them to be very reliable.

Now, I have seen two dozen or so inverters blown due to overvoltage. Power-One in North America charges a standard repair fee of $1,000 for those, and that includes shipping the unit back to you (shipping to them is on your dime). What they actually do is not repair anything at all, but send out a brand new inverter. This may change in the future though if they get a repair facility going in North America.

In short, and not just because I sell these inverters, they are very, very, very reliable when used within their parameters. The expectation really is that they should work for 20+ years for the majority of them. We'll have to wait and see if that pans out.

-Rob-

[clintonbriley]

Thanks for the information Rob.
Clint

[willib]

Forgit to include the link to my Genni 
here it is:

http://www.kleinwindanlagen.de/Forum/cf3/topic.php?t=2851

Max

Thats a real nice machine..
Start a new thread on it .

[Rob Beckers]

Max, regarding your questions about the current limit of the Aurora:  Since you mention 7200 Watt I assume you're talking about the PVI-WIND-INTERFACE box from Power-One? That is just a glorified rectifier with some other stuff, and you can easily make your own (or rather, just buy a 3-phase rectifier, for less than $100 you can get one that's rated at 1200V and 100+ Amp, so you'll never have to worry about blowing it). The inverter itself, the PVI-6000-OUTD-US-W (or the German equivalent you have over there) has an input current limit of 36 Amp.

If you provide some more information about the turbine, in particular the exact rotor diameter, and some info about the alternator (ie. how much heat loss is acceptable before melting things) I'll take a stab at making an MPPT table, and I'll explain where the numbers come from so you can make your own adjustments. Do you have the AC phase-to-phase open voltage at a higher RPM by any chance?

-Rob-

[nekit]

Rob Beckers

I'm also using the Power One PVI 6000.  You can see all the specs here     http://fieldlines.com/board/index.php/topic,144309.0.html/  in the "diary" section of this web site title "My 17' turbine so far"

If you don't mind I would love to see what kind of a MPPT curve you think would be best for my setup.

Thanks for the help.

[imsmooth]

Calculating the MPPT table values:

http://www.mindchallenger.com/wind/axial14a.html

[Menelaos]

Hi Rob,

Thanx for your offer!

The rotor diameter was supposed to be 6 meters. I am currently thinking about making it 7 meters but lets assume 6 for now.

The blades will be of this kind:

http://www.windenergie-technik-crome.de/ProfilCK220.htm

I also have the programm for those blades.
So I do know that the cp at TSR 6 will be about 42%. I can calculate the efficiencies for other TSR and Things like that as well.
As the blade profiles are not "twisted", I do not want to go beyond a TSR of 6.
I already have a rectifier ratet at 1600 Volts and 200 Amps, that one should do the job without any problem then :-)

It would be great to see your suggestion of a power table and the explainations.

Max

[Menelaos]

The Generator:

The resistance between 2 Phases is 1,9 Ohms. After rectifying, a load would see a resistance that is 13 percent lower, so that would make 1.65 Ohm for the calculation of heat loss in the stator.

I used wire of 1.6mm Diameter which should be ok for up to 30 Amps continious.
The generator features 12 coils with 220 turns and reaches 70 V DC at 42 RPM, so thats1.66 V/RPM

I consider 1-1.5 KW of heat losses in the stator as no problem. I hope thats all you need, or is there anything else you need to know?

Max

[jarrod9155]

Rob Beckers

I'm also using the Power One PVI 6000.  You can see all the specs here     http://fieldlines.com/board/index.php/topic,144309.0.html/  in the "diary" section of this web site title "My 17' turbine so far"

If you don't mind I would love to see what kind of a MPPT curve you think would be best for my setup.

Thanks for the help.

  Not sure if you have this up and running yet your link doesnt show it up yet running . I have a very simmiliar setup blades and all well mine are 18 foot royalwind blades Im am hooked up to a 4.2 aurora and I havent even come close to to maxing it out I far as I can tell this setup can only put out max 3,000 watts and hour  in 25 mph winds
Im on my second stator the first one wasnt made corrrectlly but did max out 3510 watts but the stator showed heat problems the new stator is wound 12 coils 275 turns  17 awg wire rotor is 18 inches  also  32 magnets . I can tell you that  I havent been that happy with performance but still tweeking it been throw two sets of blades my next move is to try to make my own blades 20 footers  The royal wind blades are awsome but not matching well with this aplacation. I find in a 7 to 10 mph wind the inverter just running draws around 50 to 100 watts  staying on invertering power but that causes it to stall in low winds even with the 18 foot blades. I have since up the tsr on the low end just to stay out of stall . Now I did just have  a windy week and was able to pump out 30 kw into the grid but took 7 days .Interested in seeing what your does to compare and also without a wind box from aurora you will find that you need to add resistance between the dc legs to discharge the capacitors in the inverter or it will stay on all the time something to do with the wire to the mill picking up stray voltage and tricking the inverter to stay on and   drawing power from the grid even when there is no wind.  Please let me know how yours goes







e

[jarrod9155]

Woops  can any one flip that for me  bet know one has ever seen one upside down ha ha