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Forum Index : Windmills : Stall---pulse start?
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| KiwiJohn Guru  Joined: 01/12/2005 Location: New ZealandPosts: 691 |
Hi Phill M. We have moved to Ashburton which is 80ks south of Christchurch. I have room for my lathe and a small turret mill. The project at the moment is a concrete bench to take the lathe, shaper, cold cut saw, drill press etc. It should be heavy enough! 
I got a four figure sum from the scrappie when I had my clean out but I kept a couple of F&Ps for potential projects. Maybe I can use them as power feeds on the mill? 
Have a look in 'Other Stuff' forum for my "Non-electric shed project". |
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| domwild Guru Joined: 16/12/2005 Location: AustraliaPosts: 873 |
Phil has said it all before what works but other tricks have not been mentioned to get around that nasty stalling problem with F&Ps: 1. Filing/grinding of poles 2. Twisting of poles 3. Buying the new rotors and rewiring 4. Floating hub 5. Offsetting of rotors with duals 6. Larger prop 7. Loading of rotor with other magnets Ideas with more electronic/mechanical complications; i.e. not KISS: 1. Centrifugal clutch a la chainsaw 2. Pulsing - Glenn's advice there was negative as even he had problems making the F&P into a motor for electric cars - complex 3. Starting motors 4. Mechanical kickers The reliability of a system is the product of the reliability of each component, e.g., if one item has a 0.9 reliability and the other also 0.9, then the whole system has a 0.9x0.9 = 0.81 reliability. Taxation as a means of achieving prosperity is like a man standing inside a bucket trying to lift himself up. Winston Churchill |
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Rastus Guru Joined: 29/10/2010 Location: AustraliaPosts: 301 |
Hi Domwild, Thanks for the additional info.I didn't know Glenn had tried pulsing,and Bob is using a larger rotor on his LG project.However I still have some nagging questions!If I use a magnetic sheild on the stator,would it be possible to actuate it using vacuum?I'm ignorant as to how much cubic air per sec is moved in light winds.The idea is to have a ventury on the tower(at least outside the swept area)with a vacuum line attached,the other end connected to diaphrams in the head to move the sheilds away once cuttin speed is reached.As wind speed increases the sheilds would remain firmly away from the stators.Once wind speed stops the diaphrams return the sheilds over the stator untill wind speed picks up again.An idea in its infantsy or is it infantile?Be kind!Cheers Rastus see Rastus graduate advise generously |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Which Glenn are we talking about? I didn't ever try pulsing, though I may have dicussed the idea from time to time. Anyway, magnetic shields and stuff, dont work sorry to say. You often hear magnetic shields discussed by the magnet motor crowd as the key to making their motors actually work, but of course they dont. It takes as much force to move a magnet shield ( ie, lump of steel ) into and out of the magnet flux path as it takes to move the magnets. As anyone who has tried to separate a F&P stator and magnet hub apart can tell you, you need a lot of force. It would be possible to make a mechanism to do this, but it would be bulky and need a independant power source, like a large paddle or another smaller turbine. This line of thinking to make startup easier is pretty natural and common, I've been there, and most of the members on this forum have been there, but the end result is always the same, its just not pratical. With grunty blades like the GEO222 or larger diameter turbines, overcoming the cogging isn't the issue it once was. A lot of the early F&P based windmills used blades designed for the axial flux alternators, high speed with lots of power but not much down low in the RPM. These just didn't have enough low down power to start a coggy F&P in low winds. Twisting the poles is one of the easiest ways to overcome the problem. Once you make the tool, you can do a whole stator in 5 minutes, and it makes all the difference to startup. Rounded poles is good too, but not as good, and you do loose a little power output, maybe 1 or 2 %. The 7 phase conversion is pretty much cog-free, but you need to buy specific F&P parts to make it work. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| Rastus Guru Joined: 29/10/2010 Location: AustraliaPosts: 301 |
Hi Glenn, I have more to learn.I had in mind that alluminium would work as a magnetic sheild,but that doesn't seem to add up with your last post.Cheers Rastus see Rastus graduate advise generously |
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Don B Senior Member  Joined: 27/09/2008 Location: AustraliaPosts: 190 |
Hi Rastus, I am coming into this thread a little late, as I had not realized that it had been started in lieu of Bob’s LG thread. In the matter of starting a cored generator with a significant cogging effect, the best suggestion that I have for doing this mechanically is to use a centrifugal clutchbetween the turbine ane the generator. Centrifugal clutches are common on many things such as chain saws and line trimmers, and all that is needed is to have the clutch weights and springs selected appropriately for the cut in speed that you want, and the power that you want to transmit. The force developed by the centrifugal weights in the clutch is proportional to the square of the shaft speed, so this helps, although the power to be transmitted is proportional to the cube of the wind speed. I think though that a centrifugal clutch could be made to work. Getting back to the idea of an electrical kick start, this diagram shows what I was suggesting: The connection can be into any one winding downstream of the sliprings (ie down at ground level), and needs only two double pole double throw relays or even switches. Relay (or switch) 1 needs to have a current rating sufficient to carry the maximum output amps from the generator, while relay (or switch) 2 is not really critical. When relay 1 is unenergised, the three windings will connect to the load as normal, and operation will be unaffected. The relay contacts are drawn with the coil unenergised. For a kick start, you would pulse relay 1 when you have sufficient wind speed for a start. You would then energise relay 2, and give relay 1 a second pulse. The first pulse may cause the blades to move except when the correct pole of the rotor has stopped directly at the winding core being pulsed. The second pulse should repel that pole, hopefully giving the blades enough movement to unstall themselves and get going. While an automatic pulsing arrangement would be nice, there is no reason why this could not be a manual operation for those maddening occasions when there is just not quite enough wind to let the blades start of their own accord. It is possible to fit blades that will start even a strongly cogging generator at not much above the minimum generating speed. The old multi blade water pumping windmills would certainly do that. The problem is that there is almost inevitably a trade off between starting torque, and operating speed and efficiency. Unfortunately, it is difficult to have the best of all worlds. Regards Don B |
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| Rastus Guru Joined: 29/10/2010 Location: AustraliaPosts: 301 |
Hi Don B, I like both ideas and think the finer details could be worked out for developement.It,s a problem that the diagram didn't happen for the relay's.The main reason I'm interested in this thread is mills can produce power in lighter winds than it takes to initiate start up,so with a little help it could tick over steadily.Its probably a general wind condition around Australia.The mindset is likely to be that "if there's not enough wind to start the mill,it's not worth worrying about"however there might be a way to change that,taking into account the efforts put towards ringing every last ounze out of mills for peak performance.Who's to say?Thanks for the input,Cheers Rastus see Rastus graduate advise generously |
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| Don B Senior Member Joined: 27/09/2008 Location: AustraliaPosts: 190 |
Hi again Rastus, Sorry about the diagram. It was contained in a word document, and I hadn't expected the diagram to be filleted out when I uploaded the post, and I didn't look at the post itself. I will try again: 
It is well understood that reasonably efficient blade sets can't produce enough torque to start themselves from stationary at at a wind speed at which they could produce useful power. This is also a problem for generators that have no iron core, and hence no cogging, but it is clearly more of a problem where there is cogging load to be overcome. However, as indicated in a previous post, cogging is not all bad, it is an indication of the goodness of the magnetic circuit in a cored stator generator. Efforts to reduce cogging by twisting the core or by increasing the air gap will almost certainly be reducing the effectiveness of the generator. It is a bit like reducing the compression of a car engine to try and make it easier to start - you will almost certainly lose something in the process. Reducing cogging will probably mean that the generator will have to turn faster for a given output. This, in turn, will probably mean that you have lost a margin of generation at low wind speeds that, while small, could provide a significant addition to the total output over a long period of time. So all you have to do is to somehow get your generator to start at its minimum generating wind speed, which is what this thread is all about. Regards Don B |
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| Rastus Guru Joined: 29/10/2010 Location: AustraliaPosts: 301 |
Hi Don B, I'll try to work out some numbers to see if there is a disparity between clutch pressure and wind force.To be ideal it would need sufficient clutch pressure to have no friction losses at low wind production speed.The possible objection to the pulse start is using power to produce low power levels.I've have the idea that I could use a 12v sola charged battery dedicated to run the pulse start circuit,which isn't robbing the generator system.It is ofcourse using power all the same.Thanks for the extra info,cheers Rastus see Rastus graduate advise generously |
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| Don B Senior Member Joined: 27/09/2008 Location: AustraliaPosts: 190 |
Hi Rastus, While a properly set up centrifugal clutch could conceivably help to get a generator with strong cogging away, it still has the disadvantage that the (uncoupled) blades would still not start to rotate until the wind speed was somewhat above the minimum operating speed. It would in fact be much the same situation as the starting of a generator that did not have an iron cored stator (ie no cogging). Despite this, once a centrifugal clutch had started a cogging generator running, I don't think that friction losses would be any consideration. Once the clutch operated, I don't think that there would be any friction losses. The only problem that I can think o with a clutch is if you plan to use short circuiting of the stator windings as a form of overspeed control in high wind speeds. You would really need to turn the blades out of the wind stream in this situation. Incidentally, cogging is not a constant additional load on the generator, just an additional force to be overcome to get it rotating. Once it is rotating, the cogging force actually alternates equally between accelerating and deccelerating the rotor. On the matter of the power used to kick start a generator, the duration of the pulses would be so short that the amount of power used for this would be negligible in the total scheme of things. It is really a matter of comparing the amp-hours used for the pulses as against the extra amp-hours that you are able to generate by starting in low wind speeds. You could think of it in the same way as the power taken by the starter motor in your car. The starter motor draws maybe a hundred amps from the battery, but for only a few seconds. Once the engine is running, the alternator would replace that power in less than a minute. Regards Don B |
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BobMann Senior Member Joined: 30/06/2011 Location: United StatesPosts: 134 |
Hello I done a lot of testing on this from a building view. I am the maker of the Tree Top Wind Mill witch used a car alt PMA from MWAS using a gilmer belt drive at 2.7 to 1. A lot of things come into play bearing drag,grease,weight,belt drag all this take HP to move than you come to magnet cogging. 
all of this stuff must live in some of the most bad ass weather around. I have a few of this units up and running fine over the USA. I have found making it simple and killer strong with less moving parts is best. So I have moved on to the F&P 60 and made up the Mann Smart Drive and with a lot of help from you guys and Bob Down Under I have made a very nice machine. As bob has found out to much Neomagnets can be to much. So I have found it needs to start with the build there is all was so kind of give and take here. 
I found this to work the best so far not to big of a Neomagnet you all was can go big later. just the right angle to free up some of the cogging. Now you can cut the OD of the stator to fine what works best for you. I do like the idea to power up the stator to move it some thing I will try. And if it breaks it must not lock up the turbine.So if you do not brake free at the 20MPH mark with out a start system you must go back to the build. I have found for me and a way so we can all be on the same page is use a inch pound torqe wrench it is a standed way in the world to test some thing like this. At this time I am at 14 inch LB to brake free and 5 inch LB to keep it moving at the center. These numbers can be adjusted by air gap,grease,bearing change and pre run in time. and a few other tricks but at what gain or lose and cost. Now at what speed do you need to start to make any power it is all about the wing unit. A HAWT or VAWT I wish to make some power just below 10 MPH just because it is spinning at 10 MPH do,s not mean it is making power as some of us know some turbines make nothing till they are spining up there in the sper high range. Just some of my views and tested time and time again because I break alot of stuff. Bob Mann |
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| domwild Guru Joined: 16/12/2005 Location: AustraliaPosts: 873 |
Glenn, Sorry, t'was you I had in mind when I commented on pulsing. I remember your remarks some time back, that you tried "pulsing" for motors in electric cars; I do not know if you were using F&Ps back then. You commented on it being rather complex. I hope my memory has not deserted me altogether! Taxation as a means of achieving prosperity is like a man standing inside a bucket trying to lift himself up. Winston Churchill |
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| Rastus Guru Joined: 29/10/2010 Location: AustraliaPosts: 301 |
Hi Don B, I plan to hold the mill in the fully furled position in exstreme events as you've concluded.I'm undecided wether to use AC or Dc to pulse start.Glenn made a suggestion to try a RC12A brushless motor control to run a F&P as a motor on another thread,so I'm considering trying it to pulse start.I quess it uses Dc supply.As far as the clutch is concerned with low cuttin rpm,there's weaker centrifugal force and clutch slip will make it less effective.Higher revs are fine. Hi Bob Mann, It's encouraging to follow your efforts in Research & Developement with your mills.It seems on average F&P can overcome cogging about 18mph and will continue to produce power at 15mph once they have started.So the idea is to pulse it to overcome cogging when 15mph+ winds are "steady".Thankyou for the ftlb specs they are helpfull.Cheers Rastus see Rastus graduate advise generously |
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| BobMann Senior Member Joined: 30/06/2011 Location: United StatesPosts: 134 |
Glenn made a suggestion to try a RC12A brushless motor control to run a F&P as a motor on another thread,so I'm considering trying it to pulse start.I quess it uses Dc supply. Hi Bob Mann, It's encouraging to follow your efforts in Research & Developement with your mills.It seems on average F&P can overcome cogging about 18mph and will continue to produce power at 15mph once they have started.So the idea is to pulse it to overcome cogging when 15mph+ winds are "steady".Thankyou for the ftlb specs they are helpfull.Cheers Rastus I to read Glenn post on that unit it is a low cost unit and can be found on EBay. I would go for the high,s amp unit. We are working on the same lines my plan down the road if I can get some funding is to build a controller that did a few things here we are working on it here but it is a slow prosess. May be you guys and Gismo can build it for my to test on the water tower. use the PC data logger hooked up to 3 anamers wind speed in a triangle on the out premiter of a wind farm use them for wind speed and drection. use the input to kick start the leading turbines at the best range of wind speed. it is if,then,eles code. The PC could do a few other thing to could lock down the units on high winds. look at wind speed to see if it is safe to re start and if done right it would suck the live out all the wind it could low or high speed. If some one can do a build I would help on the parts list I know there is a need for such a unit in the world for the low cost unit wind turbine. Bob Mann |
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| Rastus Guru Joined: 29/10/2010 Location: AustraliaPosts: 301 |
Hi Bob Mann, My progress is turtle pace but I hope to beat the hare over the line!With the PC use I'll leave that to my younger brother,he has a much better grasp of that realm.He's also taking care of battery desulphation so we've made a small start and more importantly we're determined to be successfull.So if we sort pulse start out,you are more than welcome to trial it.I'd prefer to lock down a mill manually just to reassure myself it is done.Cheers Rastus see Rastus graduate advise generously |
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| BobMann Senior Member Joined: 30/06/2011 Location: United StatesPosts: 134 |
Hello I did go to the hobby shop and talked to him. He is big in the RC cars. He said the controller would be about $50 but it is a dig signal so you have to convert to it or for testing buy a cheap hand control for testing. Run $200 all together. But this stuff runs on 12/24 volts I run my stator on hi volts so for a test I would use 3 VW fuel relay I think you would use a tranformer to kick up the volts to the stator just for start kick and let the RC controller run off a small battery. some one will have to do the lay out for it. The link to Green Power talks of the Hi Low relay form ogea?? you could combine both and have a nice low cost setup. If you guys cut up the stators for low volts 12/24 you could use it as a stand alone for testing too. Bob Mann |
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| Don B Senior Member Joined: 27/09/2008 Location: AustraliaPosts: 190 |
Hi all, In applying the KISS principle to bump starting, I would first try using a DC bump from the batteries that you generate into before moving on to anything more exotic (and expensive). For a bump start from any source, you are safest to disconnect the winding(s) of the generator from its normal load (rectifier and battery?) while you are giving it a bump. If you do not then, depending on what sort of a bump you are sending to the generator, its normal load might also load the bump power supply. This is why I used a double pole double throw (DPDT)relay as Relay 1. You also need a DPDT relay for Relay 2 if you are going to use a reversible polarity DC bump start and, referring to the diagram in my previous post, the bump start DC supply would be your batteries. On the matter of relays, finding a DPDT relay with contacts rated for the full current output of your generator might be a problem, however, single pole double throw (SPDT) automotive relays are readily available. Typically, they might be described as a headlight relay. The important thing is to make sure that they are a double throw relay, meaning that they have change over contacts that connect through when energised, and (importantly) also when de-energised. The will have to have at least 5 connection tags to do this - 2 for the coil, and 3 for the contacts. You just need to use 2 relays to make up one DPDT relay. The coils will usually be 12 Volt, and you can connect them in parallel for a 12V bump start control supply, or in series to use a 24V bump start control supply. In Oz, 60A rated 12V coil SPDT relays are available from Jaycar (cat SY4074) for $8.95 each. The contacts of these SPDT automotive relays are usually rated at at least 30 Amps, and should be suitable for almost any generating voltage that is in use. If you want to try a more complicated bump start using AC, etc, you will probably still need relays like this to disconnect the generator windings from the normal load while you connect the bump start system. Regards Don B |
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| Rastus Guru Joined: 29/10/2010 Location: AustraliaPosts: 301 |
Hi Bob Mann, Thanks for the effort you went to following my last post.Your feedback has lead the topic further along. Hi Don B, The previous description and circiut diagram you provided are the basis for the current discussion.Thanks for the latest clue about the mill load.I'm wondering,if the mill is unloaded when pulsed to start and then the load is suddenly applied if it would tend to return the mill to stall.What do you think? Is it likely? At present I'm contemplating the value of AC pulse,with a parrallel circuit of mill and pulse electricals.The pulse circuit includes an isolating switch.To address the rotor stop position and succesfully pulsing every time I'd include the motor stop senser of the F&P washing machine along with the motor control board.That's my latest pipe dream!All comments welcome.I just hope I can understand them Cheers Rastus see Rastus graduate advise generously |
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