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    Default OT Direct Drive wind turbine generator design

    My grand niece is in high school. Nice kid, smart. Sunday dinner, she asked me - I'm her font of technical explanations - how does a direct drive wind turbine work. I went: "Uhh-h..."

    When I got home, I surfed the web until my finger fell off but all I could find is "black block" diagrams like the ancient map makers placed "here be dragons" and Siemens videos of schooling fish and CG fly arounds of wind turbine pylons mixed with yokels and their whirling trash sculptures. .

    Permanent magnet? A jillion poles? Variable RPM constant frequency? WTF? Somehow some where there has to be info detailing the generator and its control interface with the grid. Blade pitching, asimuth control, siting, world winds, weather cycles, geography I can fake from general knowledge, but the guts? No. Bllank spot.

    Can anyone point me in the right direction for technical information on how the generator and control of a multi megawatt wind turbine work?
    Last edited by Forrest Addy; 04-21-2015 at 09:57 PM.

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    alternator with gearbox, rectified to D.C. sent down to base, big arse invertors synced to grid.

    Or this:
    http://www.gepowerconversion.com/pro...peed-generator

    Looks like there are some 2.0 mw permanent Magnet generators....yikes

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    My info is years out of date but I think the big turbines have a gearbox to increase rpm into the generator. They do make small homeowner direct drive windmills I believe they are using a 400HZ washing machine motor and running it to get 50 or 60 hertz output. Or some use a dc motor rated for 400 volts and run it slow to get 12 volts generated.
    I believe 400 hertz was common in aircraft of WW2 surplus vintage stuff.
    Bill D.

    To Be or Not to Be - Wind Turbine Design ? The Most Amazing Windmills in the World | Wind Power

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    Hello
    Lots of DIY small generators are based on a direct drive motor designed in New Zealand.
    I have one of these washing machines. There are only two moving parts, the agitator and the pump rotor.


    YourGreenDream - Hobby alternative energy production education and resources. Fisher and Paykel Smart Drive generators for windmills, windpower and hydro generators.

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    ENERCON
    Enercon in germany makes direct drive wind turbines.

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    Forrest - many ways to skin this cat using high pole count direct drive motors. Alxion is used quite a bit in the small to mid-size wind turbine designs.

    Wind turbine alternator | Alxion

    I have designed a number of generator control systems (300kW and smaller) using this type of permanent magnet generator. The biggest drawback is overspeed control - we have also used high pole count induction motors that allow you to remove the reactive power and overspeed without risk of electrical damage to connected equipment (as long as it can hang together mechanically which isn't nearly as big a problem with the smaller units)

    Also recently commissioned an Etel system - 176 poles!

    These systems have been remote with islanding and anti-islanding capabilities and up to 500kWh of battery storage - good for setting up a microgrid in a remote area. Standard Siemens S120 inverter connected to the generator and regenerative line module(s) (ALMs) with UL1741 certifications connecting to the grid.

    Same general technology as deployed here - http://www.lucidenergy.com/ . . . we put this system online between Christmas and New Years a few months ago.

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    And aside from the tech details, you have an opportunity here to include her in the search. Easy things like: Refining searches using the already-found links, looking at Google (and other) patent repositories, manufacturer's exploded parts diagrams for repair, Mother Earth News "plastic barrel" turbine construction articles, and even reviewing the responses here, together, can help her "find out how to find things out" if they're not on the first Google page. Helping her learn how to dig deeper than Google will help her quite a bit as life goes on. Could be fun, too!

    Chip

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    Ah... if you look at the last sentence of my OP: "Can anyone point me in the right direction for technical information on how the generator and control of a multi megawatt wind turbine work?"

    Home style, got it pretty well covered. I was referring to the hilltop whoppers with 300 ft rotors that would daunt the Jolly Green Quixote.

    Does the generator work like a giant Samsung washing machine motor?

    How do they center the PM rotor on the stator? Gotta be megatons of magnetic force if it ever gets eccentric. Hell it was a chore centering my 1/24 scale slot car armatures without chipping the magnets.

    The solid state power devices must be either stupendous or massively parallel - or both.

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    Quote Originally Posted by Forrest Addy View Post
    Ah... if you looks at the last sentence of my OP: "Can anyone point me in the right direction for technical information on how the generator and control of a multi megawatt wind turbine work?"

    Home style, got it pretty well covered. I was referring to the hilltop whoppers with 300 ft rotors that would daunt the Jolly Green Quixote.

    Does the generator work like a giant Samsung washing machine motor?

    How do they center the PM rotor on the stator? Gotta be megatons of magnetic force if it ever gets eccentric. Hell it was a chore centering my slot car armatues without chipping the magnets.

    The solid state power devices must be either stupendous or massively parallel - or both.
    I thought my link covered the 1.5 mw and up models....
    Let's try this one:
    https://renewables.gepower.com/wind-.../turbines.html

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    On a related note I've always had an idea to more efficiently harvest power from a home-based wind turbine.

    The following applies mostly to home-based turbines and is not at all applicable to large-scale stuff.

    The turbine is typically a 3-phase generator that is sent down the pole and rectified into DC, then fed into a battery bank or grid-tie inverter. If fed into a battery bank the charge controller is likely a PWM controller (the benefit of running a MPPT controller on a windmill is minimized). The downside to PWM controllers is, if your voltage is below the charge voltage of the batteries you get no power, if you charge voltage is significantly above the voltage of the bank you're wasting power when the PWM controller breaks circuit to limit the voltage. Very few, if any, home based turbines have a turbine speed governor that changes the pitch of the blades; so when winds vary so does your voltage. That's a problem for the simple PWM charging scheme if you're looking to harvest everything the wind can throw at it.

    My idea is two-fold, where-in one, or the other, or both changes could be incorporated in some manner.

    First off the stator, that houses the windings is on an electric actuator that can control the distance between the rotor (permanent magnet) and the stator to effect changes on the EMF, and therefore change the voltage as the wind changes.

    The 2nd idea is staged windings where-in there are 4 separate sets of windings laid over the top of one another that can be controlled in 4-series, 3-series (leaving 1 open-circuit), 2-series/2-parallel, or any number in parallel. The 3 & 4 series arrangement would allow some energy to be harvested in lower winds yet still allow the windings to switch to 4-parallel in high winds to take advantage of the vest amounts of current that can be dumped into the batteries.

    Using this approach would mean that you wouldn't have to furl the turbine out of the wind nearly as often because it would have a much wider operating range.

    Of course the ideal situation is to have a speed-governed blade-pitch system that would completely negate the necessity for any of that.

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    Quote Originally Posted by CountryBoy19 View Post
    Of course the ideal situation is to have a speed-governed blade-pitch system that would completely negate the necessity for any of that.
    Which is what a Mr.Jacobs did....

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    Quote Originally Posted by Forrest Addy View Post
    Ah... if you look at the last sentence of my OP: "Can anyone point me in the right direction for technical information on how the generator and control of a multi megawatt wind turbine work?".....


    Forrest,

    Here's my favorite link to send folks to- http://drømstørre.dk/wp-content/wind...wres/index.htm It's pretty basic, but it's a start .

    Now not all multimegawatt wind turbines are PM - that's a relatively recent development as neodymium magnets come down in price. The magnets also, unfortunately, lose their magnetism when they get hot- over 80 deg C and things start to get wacky. And their inverters have the disadvantage of having to handle full power, while variable reluctance induction generation (presently iterated as Dual Fed Induction Generation- DFIG in the parlance) only needs electronics to handle 30-40 % of the power..

    So most large wind turbines are still induction generators of various ilk driven by planetary speed increasers. It's a design pioneered in the '50s by the Danes (see Gedser mill) and 50 some odd years of development ain't gonna go away overnight.

    Here's a piece that goes deeper. Which Wind Turbine Generator Will Win?

    Here's another overview of various types of large WTG generation, including axial flux.

    http://www.google.com/url?sa=t&rct=j...91427555,d.cWc

    How do they center the PM rotor on the stator? Gotta be megatons of magnetic force if it ever gets eccentric. Hell it was a chore centering my 1/24 scale slot car armatures without chipping the magnets.

    Some of these designs are axial flux, which is a disc-shaped stator made of individual pie shaped coils, stimulated by steel backed magnet rotors on both sides of the stator. So no centering required, but lots of force there, too.

    Helpful?

    Neil

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    I have seen a few big eggbeater type windmills where the generator sits on the ground. This means there is less structure and weight in the air. Of course these are smaller, less then 100' tall, so they do not go high enough to get into the better winds.
    The Siemens sit talks a little about their direct drive generators. read about 1/2 way down this link. These are for machines with about 100 meter diameter rotors. The blades are huge, hauled on special overlong trailers. Must need special permits to move them on the road. If I read it correctly the nacelle, generator and rotor together weigh around 130 tons.
    I do not really know why but the claim is these big machines are safer for birds flying around. They have forced the smaller machines to shut down in bird season at Altamont Pass near San Francisco bay.

    Bill D.

    http://www.energy.siemens.com/co/poo..._family_EN.pdf

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    Quote Originally Posted by neilho View Post


    Forrest,

    Here's my favorite link to send folks to- http://drømstørre.dk/wp-content/wind...wres/index.htm It's pretty basic, but it's a start .

    Now not all multimegawatt wind turbines are PM - that's a relatively recent development as neodymium magnets come down in price. The magnets also, unfortunately, lose their magnetism when they get hot- over 80 deg C and things start to get wacky. And their inverters have the disadvantage of having to handle full power, while variable reluctance induction generation (presently iterated as Dual Fed Induction Generation- DFIG in the parlance) only needs electronics to handle 30-40 % of the power..

    So most large wind turbines are still induction generators of various ilk driven by planetary speed increasers. It's a design pioneered in the '50s by the Danes (see Gedser mill) and 50 some odd years of development ain't gonna go away overnight.

    Here's a piece that goes deeper. Which Wind Turbine Generator Will Win?

    Here's another overview of various types of large WTG generation, including axial flux.

    http://www.google.com/url?sa=t&rct=j...91427555,d.cWc


    Some of these designs are axial flux, which is a disc-shaped stator made of individual pie shaped coils, stimulated by steel backed magnet rotors on both sides of the stator. So no centering required, but lots of force there, too.

    Helpful?

    Neil
    Good article, some of the same points of debate come up in deciding on direct drive vs geared drive light electric vehicle drivetrains

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    I don't know of any specific good sites for info, although there must be some out there.

    BUt, since we have had wind turbine clients, WITH direct drive turbines, mebbe I can throw in some good quality confusion.....

    There are several "common" varieties of utility scale turbine.....

    1) induction generator types. These have to spin at a fairly fixed speed because they are essentially an induction motor hooked to the mains, and then spun by the wind ABOVE normal speed by an amount similar to the amount (slip) they would be slower than synchronous as a motor at that power level. Their speed therefore varies slightly with power output.
    Yes, they need a whole bunch-o-poles to be direct drive at 60 Hz and spin at a reasonable speed. And they need variable pitch blades to control speed and torque as wind speed varies.

    2) Direct connection synchronous types. These have regular synchronous motor type generators, with a field and armature. The field may be a DC field, but these days is more likely to be permanent magnet for efficiency and to avoid runaway if the field fails.
    Again, they are fixed speed, need a whole bunch of poles to stay at a reasonable RPM, and they need variable pitch. They tend to be large diameter, like an old-fashioned slow speed diesel generator.

    3) Indirect connection generators. These can spin at any speed, and don't necessarily need variable pitch, although it may improve operation. They are generally permanent magnet types, but instead of being connected to the power mains directly, they are connected through a dual inverter system.

    The input inverter operates in reverse to take the generated AC, rectify it, and boost it to a DC link voltage. The second inverter takes that DC voltage and puts it out on the mains as AC. Usually the output inverter is programmed to hold the DC link at a fixed voltage, and the booster inverter is programmed to just take whatever the generator gives it, and boost it into the link as a 'current source".
    To hold the DC link voltage, the output inverter varies its power output (by varying output phase slightly). If voltage is high, it sends more power out, or vice-versa.
    What this does is to decouple the turbine speed from the line frequency, and let the turbine utilize virtually any wind power input, from just covering system losses, up to the maximum capability of the inverters and generator.
    They still need a reasonable number of poles, to keep the generated voltage reasonable at slower speed. But their speed and output voltage can vary quite a lot while still putting out solid 60 (or 50) Hz power.

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    One thing that the Siemens article mentioned is their design is a little smaller then others. This allows them to go on standard size trailers and on most roads and bridges. Still to me 70 tons seems like a heavy load. the nacelle is 4.5 meters wide so I think that is oversize but, only a little oversize so no huge restrictions.
    Something I would not have thought about as a design consideration. I wonder how many cranes are around that can lift 145 tons to 120 meters. I bet they cost a lot to rent.
    Bill D.

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    If they are multi megawatt they center them the same way we centered 200 ton rotors in 500 ton stators. Align the bearing housings. Bump back and forth if needed, shim if needed.

    Endbells have some clearance.

    Actually, I would think (but do not KNOW) that they are more accurate IN their machining. Moving a stator or a rotor on Terra Firma is easier than 200 foot in the air.

    Are they Actually PM rotors? Or are they PM stators? Or are any of them PM? Seems to me,copper wound would be cheaper and better. May need excitation but that can be achieved with a rotating rectifier or any external excitation.

    Elaborate, please. A rotor never goes eccentric, because, as you of all people know, a long heavy shaft is NEVER allowed to not be turned to keep sag out of it. 67" rotor WILL sag when it does not turn slowly. As you often say, 50' prop shaft, 12"D will sag.

    How big ARE actual wind turbines. I thought they were in the 100 KW range.

    George

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    Quote Originally Posted by digger doug View Post
    Which is what a Mr.Jacobs did....
    I'm not sure what you're implying, your link went to something entirely unrelated to wind-turbines. Maybe it's that stupid advertising BS again... I've about had it with this new site format.

    I wasn't trying to say that mechanical governors couldn't be used. They are definitely used on large-scale turbines (likely electro-mechanical), but they are less common on small-scale, home-based turbines due to the complexity and added maintenance. For many of us on this site a mechanical or electro-mechanical governor on a home-scale turbine would be a piece of cake and maintaining it would be no problem. But for most people it's over-complicating a system that already seems like "magic" to them.

    The maintenance alone is a big deal. Moving parts fail. A home-based turbine can go through THOUSANDS of blade-pitch adjustments per day, thousands of cycles per day over the course of a year and you better be doing some pretty regular maintenance on your turbine. The challenge is that most home turbines aren't large enough to have a permanent means of doing that maintenance so the owner must lower the turbine, get a bucket truck, etc to work on it.

    That being said, I do know that there are small-scale turbines, even home-built ones, that have blade-pitch governors on them. Fieldlines forum (the PM of alternative energy) has a well-known member that is running (IIRC) a 22 foot diameter turbine with a mechanical fly-weight governor system built into the blade hub. There is also a member that is utilizing an electro-mechanical actuator through a "slip-ring" type of device that runs through the turbine spindle to electronically control blade pitch.

    The added advantage of doing the electro-mech method is you get more active control. The purely mechanical method run through a wider range of turbine rpm simply because that's the nature of the beast (as winds increase the speed of the turbine has to increase to effect more change on the fly-weights, meaning there will be small speed increases due to wind increases). The electro-mech method can theoretically be controlled however you want it to depending on how elaborate you want to make the control scheme. The problem is that mechanically this is outside most peoples ability and of those that have the mechanical ability, very few have the electrical/programming ability as well. Which essentially takes turbine speed governors out of the realm of possibility for most home turbine builders.

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    Jacobs wincharger, the pretty much "model t" of wind generators.

    Has a pitch change mechanism, and yes, made to make thousand's of changes a day.

    Had a neghbors apart to repair. (It had made a couple too many pitch changes, and needed re-bushed)

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    Quote Originally Posted by CountryBoy19 View Post
    I'm not sure what you're implying, your link went to something entirely unrelated to wind-turbines. Maybe it's that stupid advertising BS again... I've about had it with this new site format.
    Wasn't Digger's link. Prob a "Viglink" link. Hover over it and see what pops up. Dunno what browser you're using, but something called Ghostery works for Firefox. And if you elect to have Ghostery show what it's blocking, you'll be surprised (or maybe not, if you're one of those damn cynics ) at how many companies are mining and tracking and linking here. This page, for instance, is haunted by Tradedesk, Doubleclick, Google Analytics, Google Tag manager, Addthis, and Viglink.

    Battling the forces of E-vill is very satisfying.

    Neil

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