Induction Generators and Grid Tie controls

[(unknown)]

How is synchronization achieved with the Grid using induction motor/generators?

I'm searching for a complete review and practical application data of what is often referred to as asynchronous generation. I'm working on a small Bio-Diesel setup on our property and wish to have a grid tied system without the need of storage batteries, inverter, etc.

Please be aware I've read most information on the WEB and how the grid excites the induction motor and how slip both positive and negative play a part - I'm now seeking either a engineering manual or a very comprehensive how-to practical approach book, that will take my knowledge beyond the typical WEB site explanations. If someone knows of a publication/book that explains this subject matter please post it here as a respond so others may also locate the information.

Thanks for all your assistance in this matter,

FT

P.S.

I'm still open to WEB information if you know of an exceptional site that explains Grid Synchronizing of Induction Generators.

[Phil Timmons]

Hey, Texas?

Mrs. Phil tells me you can always tell when someone is from Texas, because they will tell you.  What part of Texas?  Not to be nosy, but I am playing with some similar stuff in the Dallas area.  At least on the generation end.  My bias was a Solar Boiler and turbine as the power source.

Actually I have some detailed file somewhere (I think ) that I pulled from the net a year or two back.  Guess I should try to find it one of the hard-drives.  Anyway, it was pretty old stuff, and used a freq meter to detect grid power loss a and large relay/contactor to disconnect if the grid were lost.

Like you say, the general info is that you use the concept of slip towards the power production end of the world by over-reving the motor.  Should work, we sort of do dynamic braking on equipment the same way.  A consideration for the old bridge crane conversions we do that to is that the motor insulation be of good quality and condition, as a load is a load and it generates heat and stress.  

Anyway, if we find some good up to date stuff, OK, but if not, we can build it and figure it out.  I have plenty of spare parts and motors to play with, and a shop for this type stuff.

Is your bias three-phase equipment, or single-phase motors?  I have either, but sort of figured that single phase 240 volt motors would be best, since that is what normal people have to work with -- and figured I would open-source it all, so that Joe and Jane Normal can replicate it.

But if you are interesting in figuring it out . . . let's play!

oh, hey, looking at your post again, I follow that as far as sync'ing them, you let them come up to speed under grid power (automatically syncs that way) and then you just over-rev them with your power source.  

[(unknown)]

Thanks for the response...

I'm in the Austin Area...

Let me repeat what I believe you state in you last statement...

A.) I connect an Induction Motor to the grid and it begins to run

    off the Grid's power as a motor therefor it is now in Sync

    with the grid at exactly 60Hz. For the sake of this discussion

    lets say this is a 4 pole motor which will rev at the lower 1800 RPMs

    and deliver 20HP at the shaft.

B.) Once the motor has reached its stated RPM

    1. I then must rev my engine to 1800+ RPMs

    2. I engage a clutch of some type at which point the Induction Motor

       starts to generate power instead of consuming power becuase the

       the engine is accelerating the motor above the required RPMS by X %

Okay - this seems simple enough to accomplish.

However if I'm driving the Induction Motor/Generator faster in

order to drive it into generation mode by the very nature that

it is turning faster than needed at what point will the induction

generator come to be out of phase with the grid due to the very need

to accelrate above the rated RPM?

Regards,

FT

P.S.

At this point I'm staying with 240V single phase. My home doesn't

have a 3 phase service drop.

[Phil Timmons]

I LIKE your style.

You took what was stated to you, and repeated it back clearer than it was said to you.

Have you studied Stephen Covey?

------------------------

Let me add another detail to this -- it is called "slip."

The nominal RPMs you listing -- 1800 for a 4 pole motor -- are not what actually come out of the shaft.

(and let me add for other readers, 3600 rpm for a 2 pole, and 1200 for a 6 pole motor)

The real RPMs under load are closer to 1725 (or so).

The difference is the lag.  In that lag field is where power transfer from the electrical and magnetic energy are transferred to the mechanical domain.

Maybe think of this like wind on sailboat that is just running with the wind, with the big spinnaker parachute sail up.  It does not go quite as fast as the wind, but it is dragged along by the wind.  That is what the electromagnetic field does to the shaft.  It drags it along, but there is some slip.

Now when it comes to our area of interest, we are going to push it faster.  As we go faster than the field the power is pushed and dragged by us.  So ideally we should be able to speed up the rpm of the motor by the difference of full load slip added to the nominal no-load speed and it should produce the same of amount of current being pumped back up the system as the motor would consume at full load.

So putting that into our sample model of an 1800 rpm motor, which has a full rpm of 1725 (means slip = 75 rpm) -- gives if we are connected to the grid to energize the field and we turn it at 1800 + 75 rpm, we should be pushing the full load current up the grid.

The overall system voltage stays about the same, the frequency stays the same, it is just we are a "source" of current rather than a "sink" or consumer

----------------------------

Let me re-state, that I have never personally done this in the real world.

But that is my understanding (and I am not particularly a stooge in this field ) and it seems reasonable.

A couple of cautions are that the motor was not designed or built to be such a generator (which does not mean it will not do it just fine), and many motors are not built to do their job continuously, and/or at full load.  So doing this may violate warranties, and UL listings -- as well as possibly toast some things while we sort it all out.

---------------------------

About your application -- 20 hp systems are big enough to real exciting (in a not so good way) if something does not work well, as well the components tending to be expensive.

My end goal is to run a few parallel 10hp units at about 70% of capacity.

I would propose we try this with some 1 to 5 hp sized equipment to get started and see how that does before we blow-up some big stuff.  

I have some of that type stuff, along with pulleys, belts, relays, motor starters, breakers, mounting frames, and I think about everything we will need for some low power tests.

[(unknown)]

I decided to add a drawing to assist me in asking question(s) that will further assist me collect the information I need to succeed with my project.




In all the discussions of Grid tied systems the comment is made a facility must be made to sense that the power from the Grid is present and if it is not the disconnect must remove my system from the grid. I completely inderstand the need for this function.




However, If I'm generating more electricity/power than what is being consumed by my personal use therefore the excess amount(s) of power are flowing into the Grid - if so, how in the world will the Grid tie components sense the presense of the Grid; being power is flowing into the Grid not into my Grid Tie connection point?




Best regards,

FT

[(unknown)]

Phil,
Yes I have studied Stephen Covey and many other Six Sigma quality sources.



I believe I understand your comments:



   A.)   There is a slip of 0.0416%

   B.)   If we counter the slip by the offsetting percentage it will

        create a Delta of 0.083%

   C.)   Start small and test taking all precautions.

   D.)   Tests should have well defined objectives in

        controlled environments.




So let's define a basic scenarios to build upon. All input being welcome. Open forum to all members



Criteria:

1.)   Safety is our Prime Directive

2.)   Create a MOP for each test. (MOP = Method of Procedure)

3.)   Post MOP on Forum to receive suggestions and cautions

4.)   Take all suggestion under advisement - Agree or Agree to Disagree

5.)   Document Test Environment

6.)   Document Results

7.)   Post Results

8.)   Have Fun




In light of your suggestions I will use the Grid with properly fused/breaker circuits, I will install a dedicated ground receptacle in my shop bench to use. I'm sure I will pop the breaker more than once in learning how to properly adjust the motor into generation mode.



I will find a used low power Induction Motor to start testing with - off I go to the surplus store.



I will use another electric motor to drive the Induction Motor into generation. I will have to device a speed controller for the mechanical drive motor.



I need a clutch to connect these two together - open for all suggestion...




DVM (in hand)

Amp Meters (need)

Oscilloscope (in hand)

Power Meter (in hand)

Hand tools (in hand)



Will a typical Surge Suppressor available at all computer outlets assist in reverse?  I don't want to blow the electronics in our home by my testing in the shop.  



Other suggestions?....



Regards,



FT

[Phil Timmons]

Ahh, good question.  Being a perfectionist EE, myself, I am less than happy with I have gotten for an answer to that, as well.  In my first reply I mentioned something about a frequency meter.  If the local generator (that would be our equipment) senses anything off of the steady 60 hz (US and Texas) that the grid is forcing on everything connected, it would "know" the grid was open and open the big contactor/relay that would be part of our equipment disconnecting means.  So you are then disconnected from the grid.  

Without the grid to hold our local voltage system steady at (for our purposes) 240 volts, 60 cycle, it would drift to a higher frequency since we are slightly over-running our motor/generator, and probably some unknown higher voltage depending on our local load.

If you look at a stand-alone back-up power generator that is separated from the grid by a transfer switch/relay, they have a governor/frequency counter that varies the throttle for the engine speed to create the 60 hertz on a local system as the actual electrical load varies, and voltage regulators.

If we do our controller correctly, our system would only try to speed up to the limit of the nominal RPM + slip RPM, while watching the current being produced up to the limits of the current carrying and producing capacity of our system.    

There are some other aspects we should ask about, as well:

(just a sample, not meant to be everything.)

1. Power buy-back policies.
   
2. Insurance requirements as an energy producer, and of course --
   
3. Taxes.
   
   

I am in a yahoogroup with a bunch of policy-wonks and some PV production contractor types who will probably know those things.  It is called North Texas Renewable Energy Group.  (ntreg@yahoogroups.com).  You may want to sign on to them.  They discuss a lot of things that are on this board, as they effect the Texas environs.

Another thought about your diesel engine connection  . .  yeah, I suppose a clutch would be a reasonable connection between the engine and the motor-turned-generator.  With a turbine (my bias) you could just let it coast up to speed and then hit it with throttled steam to run the speed into the generating range.  Not that I am promoting it, you could use a bio-diesel fired turbine.  It may get better "mileage" than a piston engine.  But that (mechanical) is outside what I really know well.

There is a homebrew turbine group you may want to look at:

http://phoenixnavigation.com/ptbc/home.htm

A note -- They are Tesla folks, if you are familar . . . and yeah, I know, Tesla folks tend to be a little "out there."  But these guys do everything open source and on-line, and have produced working equipment.

[Phil Timmons]

Well that is OUTSTANDING!

Can I hire you?

Whew.  Outstanding.

And I am with you on safety first.  The Wright Bros. may have been their own test pilots, but I cannot see where any of this is worth getting killed or even hurt over.

As far as a good safety protocol, let me think that over tonight.  I tend to wake up thinking about stuff like this.

I would not fully declare that a surge protector would keep everything safe.  Let me ponder that, too.  

I have some surplus motors, relays, pulleys, and belts around if you would like to try them, too.  I am thinking a belt with slightly different pulley sizes would do the trick.  The smaller pulley motor will overdrive the slightly larger pulley motor and turn it into a generator, if this stuff works correctly.

Your test equipment list sounds good, and I will probably breadboard up some sort of freq. counter to check actual shaft speed and probably some sort of current metering device.  I have commercial "amp-probes" -- they clamp around the wire, but also probably thousands of surplus solenoid coils that can be used as current transformers.

And yeah, sorry to everyone else as far as hogging this conversation.  If anyone sees anything they know is not correct, or safe, please set us straight.

[(unknown)]

Phil,

With your information to guide me, I started a different search and I came up with the following information that a typical Grid Tied system posses. With your information, I now fully understand each of these items:

Grid shorted --

  Normally, when the utility power fails, the Grid Tie System momentarily tries to power the entire neighborhood. This condition looks like a short circuit to the Grid Tie System and shall cause it to reach the preset over-current protection setting and shuts off. It then opens it's internal relay and disconnects from the utility grid. This protective system operates instantly (ideally under four milliseconds).

Grid open --

  The Grid Tie System shall tell when there is no current being delivered to the grid and it will disconnect. This is used when a disconnected switch is opened or the power line which feeds the installation is cut. This protective system may require up to one second to respond.

Islanding --

  This occurs when the grid has failed and the "neighborhood" that the Grid Tie System is powering requires the same amount of power that the Grid Tie System can supply. This balanced condition is often called "islanding". The islanding detection circuit shall check the grid condition on each cycle. The Grid Tie System  shall watch the utility grid and waits for it to rise a couple of volts before it begins to invert again. This is done on each cycle when SELL mode is activated. Typically, disconnection is achieved in a few cycles after the utility has failed. If a large electric motor is connected, it may provide enough generator capacity that the Grid Tie System  thinks the grid is still connected. This can fool this protective system. Two additional protective systems must be provided to then handle this condition: over/under frequency and over/under voltage detection.

Over/Under Frequency --

  Since the Grid Tie System shall lock onto the frequency of the "Islanded" utility grid, the frequency of the system will drift out of regulation in a short amount of time during an islanding condition. This protective system may require up to one second to respond. The Grid Tie System shall shut off disconnecting after the frequency exceeds +/- 1 hertz of the nominal frequency.

Over/Under Voltage --

  Since the Grid Tie System does not regulate the voltage of the utility grid while selling power into it, the AC voltage will drift out of regulation in short amount of time during an islanding condition. This protective system may require up to one second to respond. The Grid Tie System shall shut off and disconnect after the voltage exceeds =/- 10% of the nominal AC voltage.

This is ideal - If anyone knows of a UL listed manufacture of just such a box - please post the information. Every commercial unit I come across is part of a Inverter. The local utility provider requires this unit to be UL Listed - AND I FULLY AGREE! And the same is true of my insurance provider. I can setup a homebrew series of components - Generator , Engine, etc, BUT the Safety unit that disconnects my generator from the Grid must be UL listed and rated according to NEC rules! ( As you can tell from the verbage this seems to be part of a RFI or RFQ) but I've been unsuccessful in locating the unit that will or met the RFI/Q.

Regards,

FT

[Phil Timmons]

hmmm, you need a product, but the product does not seem to exist . . .

need a product, but it does not exist . . .

sounds like AN OPPORTUNITY!

I am teasing, but if that is the case, there could be a commercial demand for such a thing.

I am thinking that TXU (or other suppliers) must have spec's for this as most all utilities have at least some industrial "co-generators" on their system.  And those folks are way out of the inverter range.

A note regarding UL listings, is that we often mute the issue by building new or weird toys out of all UL listed components, and we use them in the manner intended by the manufacturer.  While it does not give us a specific listing for the assembled device, it makes it compliant.  Although I have never seen that "tested" in court.

What I am thinking is that using a UL listed frequency sensor -- with drop-out device, and using a UL listed voltage sensor -- also with drop out device, and hooking them up in a logical "AND" (means it requires both freq. and voltage) to pull in a big (UL listed) contactor/relay may meet the letter and requirements of these specifications you have found.

And a freq. counter/relay and voltage relay system sort of matches that old schematic I had.  Power equipment does not tend to advance very fast.

[Drives]

Guys:

I have "back fed" the power line with 3 phase induction motors for years.  My company uses 2 motors belted together with slightly different pulley sizes.  We repair VFD's so when we want to load test them, we start one motor with the VFD, and get it up to the predetermined speed ours is 53Hz hence, 1546RPM...pay attention to direction!  Once the driven motor is up to speed, we close a circuit breaker to connect the generating motor "across the line" it is spinning at nameplate RPM of 1750.  Then all you do is increase the driven motor's speed until you see the current that you want.  No mechanical clutch is needed.

To answer some questions, I'll present an analogy.  Could you instaneously increase the level of the great lakes with a garden hose?  No.  No matter how hard you drive your motor into generating power (the garden hose)...you will never change the voltage or frequency of the grid (the great lake) you are tied to.  The motor will not "fall" out of sync or other wise.  Just keep an eye on the current, and you will be all set.  Another nice aspect of this system is that if the grid goes down, it will stop generating as well...intrinsically (sp) safe.

Hope this helps.

[Phil Timmons]

Thanks Dean,

That pretty much matches our expectations.  One technical detail I should mention about loss of grid power -- you are correct that MOST of the time it would stop generating, but there is a condition called "Islanding" -- in other words a small "island" around the generator where things might just happen to be in balance -- power generated nearly matches power being consumed -- so that the local system stays in balance, and keeps generating.  That is the condition that makes local backfeed generation such as this not always intrinsically safe.

However, in the "island" condition the system we have been describing would then begin to operate at a slightly higher frequency (since we are operating in the nominal speed + slip mode), and probably a slighter higher voltage, since we are producing power.

That is why the safety equipment we are discussing watches both the frequency and voltage, and if either get outside the tight bounds that the fully connected grid imposes, our safety equipment needs to disconnect and shut our system down.

--------------

So I asked the brain-trust at the North Texas Renewable Energy Group about all this as well, since they do have direct experience in connecting equipment to the grid.  Most of their views regarded the use of inverter based systems.  I follow that SMA seems to be a popular brand of inverter.  Those inverters are already UL listed for connection and directly feeding onto the grid so the local utility (TXU in our case) just blesses those installations without much care.

After pointing out that our application was a little larger power output and did not use an inverter, they gave me several citations of sources and standards --

One is "UL 1741"  That is a Underwriter's Lab standard, but I have not yet looked at it, so I am not sure if covers only inverter systems, or rotating generators (our system) or both.  

One member advised, ". . . generated power needs to be synchronized to the line, which involves electronic aspects of UL1741.  This document covers issues such as islanding, disconnect/reconnect times, and much more.  For notes, the latest release of UL1741 is about 150 pages long."

And they provided other the Texas state standards for this arena as well:

"You can find the Particulars on http://www.puc.state.tx.us/

This will help http://www.puc.state.tx.us/search/rulesquery.cfm

http://www.puc.state.tx.us/rules/subrules/electric/index.cfm    Chapter 25 Rules"

and another list:

1)  Guide to Electric Choice -  Listing of Retail Electric Providers

http://www.powertochoose.com

2)  PUCT Substantive Rules 25.211 and 25.212  Interconnection of On-Site

Distributed Generation and Technical Requirements for

Interconnection and Parallel Operation of Distributed Generation (Site Map

- Rules and Laws - Electric - Substantive Rules - 25.211 - 25.212)

http://www.puc.state.tx.us/rules/subrules/electric/index.cfm

3) PUCT Requirements for Precertification of Distributed Generation

Equipment  (Site Map - Electric - Projects - Project No. 22318)

http://www.puc.state.tx.us/electric/projects/22318/22318.cfm

4)  PUCT Distributed Generation Manual (Site Map - Electric - Projects -

Project No. 21965)

http://www.puc.state.tx.us/electric/projects/21965/21965.cfm

And one member sent one set of documents that may include propriety information, so I will need to review and check with those sources before distributing them.  However, if I find anything useful to our discussion in them, I can probably separate the useful from the propriety and share it.

The march continues!

[Drives]

Phil:

I'm aware that a standard generator can cause this "islanding effect", however how can a standard induction motor continue to generate power when you remove it's source of excitation?  A standard generator has either magnets, or a seperate excitation coil that is intially powered by a separate power source.  An induction motor needs the line power...I have heard of people taking an induction motor and "zapping" it to get it to generate power, yet I don't understand how it continues to generate.  It may have something to do with the circulating current through just the right size load resistance?  I have never it seen it happen in my experience.

Using a conventional generator, I strongly support all of the safety devices that the power company demands.  Yet, even if you back fed the grid with a conventional generator, typicially (not always), but typically won't the excessive load of the grid cause your generator to draw excessive current, and open your overcurrent protection?

[Phil Timmons]

Hey Dean,

First, let me re-emphasize that I have not yet tried this in the real world . . . but this afternoon I am setting up a part of the shop for this, so Look-Out!

My real experince in this direction is VFD's, [variable frequency drives] like you.  We use them for crane controllers, with dynamic braking (turns the motor into a generator, and "dumps" the load through a big, BIG, resistor/heater bank.  And VFD's for normal motor, fan, conveyor, and test equipment drives.

What I (think I) understand about "Islanding" is that it only occurs with a larger system fault condition where an small area (small compared to the overall grid) is still connected to the generating source, and causing at least some load on the generating source.

When a back-up generator is running and pumping upstream, it is doing so with its own voltage regulation and frequency control.  So if there were a big load (bigger than the generator could handle, it bog down the generator and kick its circuit breakers.  If the load is less than the generator could handle, I would think it would continue merrily along as long as fuel were present.  That could be really dangerous to linemen, so I suppose that is why backup generators required full transfer switches.

However . . . (here comes the balancing trick) . . . if the island were being fed by an over-RPM-ed induction motor (the scenario we are discussing), there could be a condition where that local "island" was creating a load nearly equal to the output of the over-RPM-ed motor.  In that case, you could find the voltage holding its own.  Consumption would about equal to output.  That would mean the field in our over-RPM-ed motor COULD continue to exist.  (and no, for the "Free Energy" folks it would not be perpetual motion, we would be putting energy into the system via the rotating shaft).  

However, while that balanced load COULD keep the field in existence, since our over-RPM-ed motor is in fact, over-RPM-ed, the output frequency would increase, as there is no longer the larger grid to keep it subdued.  That is the reason we would monitor the frequency and drop off our system if we detected frequency variation.  The voltage may tend to float around as well, and that is why we look for voltage variation, and also disconnect if that is found.

[Vernon]

I have used a 3 phase 40HP induction motor as an induction generator as a test load for DC motors of similar power. The motor requires a thermal overload relay that will drop out a contactor and a magnetic circuit breaker for instantaneous fault protection. The motor requires exciting vars provided by the system and will not generate as an "island" for more than a few cycles if it is separated from the system. The contactor will effect undervoltage separation by dropping out. I would use a Scientific Columbus or similar watt transducer to measure the amplitude and direction of power. I would also have an ammeter in each phase (for a 3 phase machine). There is no need to synchronise anything, just run the prime mover up to the approximate speed and energise the contactor. Observe the power measurement and advance the throttle until the desired output is obtained or rated full load amps is reached, this will typically occur about 50 RPM above the synchronous speed. It is important to have an overspeed "trip" that will close the throttle should system separation occur. I might use a small tach generator and comparator for this.

[Phil Timmons]

Hey thanks, Vernon,

That is some good information.  I suppose the normal overloads in a typical motor starter would work well for what you are describing regarding overcurrent.

My first bias was towards 3 phase, as well, because that is what I have available at our location.  (240 volt open delta (high leg type))  But many people only have single phase 240, and I can use our two lower legs in a single phase manner, so I figured I would build what others could easily repeat.  

I do concur that an overspeed tach (actually a LED-based pulse counter) is a good add-on, as well.  I am using one in my test setup but it would be easy to ruggedize a little and make part of the overall controller.

and hey, not to beat an overly dead horse to absolute death, but -- the island stuff should be a very rare condition that requires a very balanced island (load of the island to our source) but the freq counter and voltage variance detection are part of what I follow the UL requirements to detect and prevent it.

[(unknown)]

Hi again,

This thread really took off...

I'm glad I came here to seek enlightenment, I can't tell you each how much I appreciate your input, but I can see that I'm not the only one that is "still" in need for truly reliable synchronization control and protection.

Through my many contacts, I was finally directed to the source. I have uploaded three file to give each of you access via this forum

I will now be able to meet all the Grid Tie requirements.

Regards,

HERE IS THE INFORMATION:

<"http://www.otherpower.com/images/scimages/3409/Synchronizing_Unit_SPM_D11.pdf" width=80%>

<"http://www.otherpower.com/images/scimages/3409/Governing_Fundamentals_and_Power_Management.pdf" width=80%>

<"http://www.otherpower.com/images/scimages/3409/PID_Loops__Training.pdf" width=80%>

I will now move foward with allocating time to building my generator... I will post additional information with photos and the project developes.

FriendlyTexas

[(unknown)]

Okay,

Thanks for this info.

I understand you analogy.

FT

[(unknown)]

Wow,

Thanks for this information. I found the same... everyone I found has experience with inverter based systems, however this would be extremely expensive for what I'm trying to accomplish.

I have located the equipment I was seeking. See posting below (same thread) just further along.

Thanks,

FT

[(unknown)]

Hi again,

Not sure why the 1st and 3rd file are not working.

I Have renamed them to see if this works...

http://www.otherpower.com/images/scimages/3409/PIDloops.pdf

http://www.otherpower.com/images/scimages/3409/SyncUnit.pdf

Lets try these...

FT

[(unknown)]

Folks this unit also looks promising...

http://www.otherpower.com/images/scimages/3409/ProtectionRelay.pdf

Later, FT

[(unknown)]

OKay...

All of you on this forum probably already knew this but I had to figure it all out one slow and time-consuming step at a time¡K  f¼

I followed this rabbit and it just does not work out.

Keeping a Grid Tied generator even with free Waist Vegetable Oil (WVO) is cost prohibitive. I thought with my source of WVO I could make the costs at least break even, but they do not. The cost of acquiring the collection equipment, collecting the WVO, Processing the WVO and the maintenance cost of the generator just blow the cost model to smithereens. While I¡¦m all for labors of love, I can¡¦t afford to create a cash drain. I don¡¦t mind if all my man hours are ¡¥volunteer¡¦ hours but at least it has to pay for its own existence.  

Soooo¡K.   I am off looking for a different way. (¡K how many ways I will learn and calculate that will not work or even be self sustaining before I get it¡K)

Therefore, I need some input on my second way of getting there.

Due to our surroundings we have a nice supply of air ( I realize that all surveys point to the fact that my area is only a Cat. 2 wind supply but it may still work for a small system). Again, here I have little to no desire to using an inverter (Trace, etc) because of the costs. However, I believe it will require batteries but if someone knows of a way around having to use batteries please let me know.

   Wind => Windmill => Charging Regulator => Batteries => DC Motor coupled to a Generator ==> Grid

Your thoughts and constructive opinions are Welcome

Regards,

FT

[powerbuoy]

Friendly:

Do you know what this Woodward multifunction relay (over/under freq, voltage etc.) cost?

Thx,

Powerbuoy